Int J Clin Exp Pathol 2015;8(2):2103-2110 www.ijcep.com /ISSN:1936-2625/IJCEP0004419
Case Report Melanotic oncocytic metaplasia of the nasopharynx: a case report with a focus on immunohistochemical analyses and literature review Shogo Tajima1,2, Aki Ohkubo3, Matsumi Yoshida3, Kenji Koda2, Ichirota Nameki3 1 2
Department of Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Departments of Pathology, 3Otolaryngology, Fujieda Municipal General Hospital, Shizuoka, Japan
Received December 3, 2014; Accepted January 28, 2015; Epub February 1, 2015; Published February 15, 2015 Abstract: Melanotic oncocytic metaplasia (MOM) of the nasopharynx is an extremely rare lesion, with only 21 cases reported in English literature to date. MOM typically occurs near the Eustachian tube opening in Asian men in their 60 s to 70 s. Here, we present a case of MOM in a 57-year-old Japanese man who is a heavy smoker. The patient did not have complaints; MOM was diagnosed incidentally as 4 flat elevated lesions with brown to black discoloration, ranging from 2 to 3 mm in maximal diameter, were found in the right torus tubarius. On suspecting melanoma, the largest lesion was biopsied. Microscopic examination identified both oncocytic metaplasia and melanin pigmentation of the epithelium in the same gland. Upon immunohistochemical examination, melanocytes displayed reactivity for 3 out of 4 melanocytic markers; immunopositivity for S-100 protein, Melan-A, and MITF and immunonegativity for HMB-45 was observed. Normal melanocytes in the nearby surface respiratory epithelium displayed the same pattern of immunoreactivity. Immunopositivity for S-100 protein and immunonegativity for HMB-45 have been previously reported in MOM. Reduction of stimulation of melanocytes in a longstanding lesion like MOM may explain the immunonegativity for HMB-45. S-100 protein, in conjunction with more specific marker for melanocytes, Melan-A or MITF, could prove the definite presence of melanocytes in this case of MOM. As it has been shown by previous reports that MOM pursues a benign course, it will be sufficient to follow up the patients regularly for the remaining 3 lesions. Keywords: Melanotic oncocytic metaplasia, nasopharynx, immunohistochemistry
Introduction Melanotic oncocytic metaplasia (MOM) of the nasopharynx is an extremely rare lesion, first described by Shek et al. in 1995 [1]. There have been only 21 cases reported in English literature to date [1-12]. MOM has typically been diagnosed near the Eustachian tube opening in Asian men in their 60s to 70 s. MOM lesions are usually a few millimeters in size with a slight elevation and show brown to black discoloration. Multiple lesions and bilateral involvement have sometimes been encountered in patients [5]. The associated representative symptoms such as otitis media and tinnitus may be caused by compression of the Eustachian tube [11]. Although MOM may be macroscopically misidentified as early nasopharyngeal carcinoma,
malignant melanoma, or nevus, it is microscopically distinct from these three diseases; MOM is characterized by an admixture of both melanin pigmentation and oncocytic metaplasia in the same gland [9]. The source of melanin was attributable to the numerous melanocytes found to coexist in MOM. Upon immunohistochemical (IHC) analysis, the melanocytes were found to be positive for S-100 protein and negative for HMB-45, both of which are melanocytic markers; only one study on MOM tested for reactivity with Melan-A, another marker of melanocytes, and found a positive result [12]. In this study, we present an additional case of MOM, where the melanocytes stained positively for S-100 protein and negatively for HMB-45, as found by IHC analysis, as was expected. We further analyzed the immunoreactivity of the melanocytes for two additional melanocytic
Nasopharyngeal melanotic oncocytic metaplasia
Figure 1. Laryngoscopical examination revealed lesions in the right torus tubarius. (A) One of the 4 flat elevated lesions found in the right torus tubarius. It displayed brown to black discoloration and ranged from 2 to 3 mm in maximal diameter. (B) (A) in higher magnification.
markers, Melan-A and MITF, and found that the cell showed positive staining for both the markers. This pattern of expression signature of melanocytes in MOM is discussed in this report and extensive review of the literature was conducted to extract characteristics of MOM. Clinical findings A 57-year-old Japanese man, who was regularly followed up and treated at a local clinic for hypertension and hyperlipidemia, was referred because of elevated carcinoembryonic antigen (CEA: 8.9 ng/ml; normal range: < 5 ng/ml) levels and a positive result for fecal occult blood test. He is a heavy smoker with a history of smoking 30 cigarettes per day for the past 40 years (Brinkman index: 1200). Upper and lower endoscopic examination revealed no abnormality. By computed tomography (CT), several nodules with central cavities in the bilateral lung were identified. Metastatic or inflammatory lesions were suspected, but the patient refused a TBLB. The head and neck region was examined to search for the origin of a possible metastatic tumor. No palpable mass was found in this region. The patient underwent laryngoscopy, and 4 flat, elevated lesions with brown to black discoloration, ranging from 2 to 3 mm in the maximal diameter, were found in the right torus tubarius (Figure 1A, 1B). Melanoma was 2104
suspected, and a biopsy was collected from the largest lesion; examination revealed MOM. Examination of the nasal cavity, pharynx, and larynx revealed no additional lesions. Subsequently, fluorodeoxyglucose positron emission tomography was performed. No abnormal accumulation was found in the lung or any other organs. Six months later, the patient was reexamined by CT. The lesions that had been initially detected had disappeared and were therefore considered inflammatory lesions. However, the patient’s CEA level was still elevated (6.2 ng/ml); the increased CEA level was suspected to be a result of heavy smoking. As the lesions of the right torus tubarius were not enlarged, he was referred back to the local clinic. Pathological findings The biopsied tissue was fixed in 10% buffered formalin. The specimen was then embedded in paraffin. Sections were cut for hematoxylin and eosin (H&E) staining (2.5 μm thick sections), Fontana-Masson staining (2.5 μm thick sections), and immunohistochemical analysis (IHC; 4 μm thick sections). IHC analysis was performed using an automated slide stainer (Bench-Mark GX; Ventana Medical Systems, Tucson, AZ, USA). Giemsa staining was used as a counterstain for the specimen used for IHC analysis. Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia
Figure 2. Histopathological findings. A. The surface of the lesion was covered by respiratory epithelium with goblet cells. It was composed of pre-existing seromucous glands with diffuse oncocytic metaplasia (× 20). B. Oncocytes presented abundant eosinophilc granular cytoplasm. Brown pigments were also observed in the cytoplasm of many
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Nasopharyngeal melanotic oncocytic metaplasia oncocytes (× 200). C. Upon closer inspection, melanocytes were hardly discernible. Mitotic figures or atypia of oncocytes were not observed. The pigments stained positive with Fontana-Masson staining (inset) (× 400).
Figure 3. Immunohistochemistry of the lesion. Giemsa staining used as a counterstain revealed metachromasia for melanin pigment. Arrows indicate melanocytes. A. Melanocytes stained positive for S-100 protein (× 400). B. Melanocytes stained negative for HMB-45 (× 400). C. Melanocytes were immunoreactive for Melan-A (× 400). D. Melanocytes were immunopositive for MITF (× 400).
Microscopically, the lesion was well demarcated, but was not encapsulated. The surface was covered by respiratory epithelium with goblet cells. The lesion was composed of pre-existing seromucous glands with diffuse oncocytic metaplasia (Figure 2A). Oncocytes presented abundant eosinophilic granular cytoplasm. Brown pigments were also observed in the cytoplasm of many oncocytes (Figure 2B). Upon closer inspection, melanocytes were found to be hardly discernible. Mitotic figures or atypia of oncocytes were not observed (Figure 2C). The brown pigments were positive for Fontana-Masson staining 2106
(Figure 2C, inset), indicating melanin or lipofuscin. IHC analysis revealed melanocytes in the basal layer and intervening glandular cells. The melanocytes were positive for S-100 protein (polyclonal, 1:1000; Dako, Glostrup, Denmark) (Figure 3A). HMB-45 did not show immunoreactivity (HMB-45, 1:100; Dako) (Figure 3B). The melanocytes were found to be immunoreactive to Melan-A (A103, 1:50; Dako) (Figure 3C) and MITF (D5, 1:100; Dako) (Figure 3D). Melanocytes also existed in the surface respiratory epithelium near the lesion, which showed the Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia
Figure 4. Immunohistochemistry of the surface respiratory epithelium. Giemsa staining revealed metachromasia for melanin pigment. A. Melanocytes stained positive for S-100 protein (× 400). B. Melanocytes were negative for HMB-45 staining (× 400). C. Melanocytes were positive for Melan-A staining (× 400). D. Melanocytes were positive for MITF staining (× 400).
same staining pattern on IHC for the 4 antibodies (Figure 4A-D). As a counterstain of IHC, Giemsa staining was performed and displayed metachromasia, where the color of pigments changed from brown to green. This phenomenon was observed in all IHC specimens. This observation, together with the positive FontanaMasson staining, demonstrated that the pigments were indeed melanin. The diagnosis of MOM was rendered, supported by the result of H&E staining, special staining, and IHC analysis, along with the results of macroscopic observations. Discussion This case of the extremely rare lesion, MOM, is the 22nd reported case (Table 1) [1-12]. MOM 2107
comprises both oncocytic metaplasia and melanin pigmentation of the epithelium in the same gland. Oncocytic metaplasia of the glandular epithelium alone is sometimes encountered, which is considered an age-related phenomenon in the nasopharynx [13] and is common in the salivary gland [14]. Because oncocytic metaplasia is more frequently encountered than melanin pigmentation in the nasopharynx, it is speculated that melanin pigmentation occurred after oncocytic metaplasia. It has also been suggested that smoking may be a predisposing factor for melanin pigmentation. This speculation is supported by the observed relationship between oral melanin pigmentation and smoking in some Asian populations [15]. Male predominance can be explained by the fact that there are more male than female smokers among Asians [5]. Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia Table 1. Cases of melanotic oncocytic metaplasia of the nasopharynx Case
Author
Year
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Shek et al. [1] Shek et al. [1] Kurihara et al. [2] Hirakawa et al. [3] Xue et al. [4] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Takano et al. [6] Lui et al. [7] Liao et al. [8] Kondo et al. [9] Li et al. [10] Na et al. [11]
1995 1995 1997 1999 1999 2004 2004 2004 2004 2004 2004 2004 2004 2004 2005 2010 2010 2012
19 20 21 22
Na et al. [11] Na et al. [11] Chang et al. [12] Present case
2012 2012 2014 2014
Gender/ Number Site Symptom Age of lesions M/67 Single Eustachian opening Otitis media M/63 Single Eustachian opening Tinnitus M/69 Multiple Left nasopharynx None M/64 Multiple Bilateral Eustachian opening, left pharynx, and nasal cavity Discomfort in the throat M/70 Multiple Bilateral Eustachian opening Tinnitus M/80 Multiple Right nasal cavity and pharynx Hoarseness M/69 Single Left Eustachian opening Hoarseness M/74 Single Left nasopharynx Rhinorrhea F/74 Multiple Right Eustachian opening Discomfort in the throat M/68 Single Nasopharynx None M/65 Single Right Eustachian opening Hemoptysis M/63 Single Left Eustachian opening Epistaxis M/62 Multiple Left Eustachian opening, and bilateral torus tubarius Discomfort in the left ear M/79 Single Right Eustachian opening Otitis media M/Multiple Bilateral nasopharynx None M/73 Multiple Bilateral torus tubarius Nasal congestion M/58 Multiple Bilateral nasopharynx Epistaxis M/72 Multiple Bilateral torus tubarius Headache and impaired hearing M/71 Multiple Left torus tubarius and soft palate Hoarseness M/51 Multiple Right torus tubarius Pain of the tongue M/63 Multiple Nasopharynx Epistaxis M/57 Multiple Right torus tubarius None
Smoking history Unknown Unknown Unknown Unknown Unknown 10/day × 50 yr 40/day × 60 yr Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Non-smoker 20/day × 40 yr 40/day × 50 yr 20/day × 40 yr Unknown 40/day × 40 yr 30/day × 40 yr
M, male; F, female; yr, year.
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Nasopharyngeal melanotic oncocytic metaplasia Melanocytes are consistently present in MOM as a source for melanin pigmentation in oncocytes [1-12]. Melanocytes have been reported to exist in the epithelium and stroma of the nasal cavity [16] and are postulated to colonize in MOM. Ultrastructurally, oncocytes in MOM lack premature melanosomes, in which melanin is produced [3]. Hence, the melanin pigment in MOM is believed to be passed on from the adjacent melanocytes via their dendrites [3]. Upon IHC examination of previous reports, there were some cells in MOM consistently found to be positive for S-100 protein and negative for HMB-45, both of which are melanocytic markers. Only one previous study confirmed the presence of melanocytes in MOM using a third melanocytic marker, Melan-A [12]. As S-100 protein is the most sensitive marker for melanocytes [17], positive staining for S-100 was expected. However, positive staining for S-100 protein does not conclusively identify cells as melanocytes due to its lack of specificity [17]. Although HMB-45 is a more specific marker for melanocytes than S-100 protein [17], it stains premelanosome glycoprotein abundant in adult melanocytes during stimulation and normal adult skin melanocytes are not stained [18]. This is a likely explanation for why HMB-45 staining was not observed in previous studies. It may also be presumed that melanocytes in MOM are not in a highly stimulated state at the time of biopsy, indicating a previously developed and longstanding nature of MOM. In contrast, we speculate that melanocytes were stimulated during MOM development, judging by the abundant melanin pigmentation. Another melanocytic marker, Melan-A, which is the same as MART-1, a transmembrane protein of melanocytes [19], is more sensitive than HMB-45 [20]. Melan-A/MART-1 stains normal skin melanocytes [19], explaining the positive staining of melanocytes in MOM for Melan-A. MITF is an integral transcriptional regulator in melanocytes and expression of this gene is required [21]. This fact may explain the finding that melanocytes in MOM are positive for MITF. All the reported cases of MOM followed a benign clinical course; there have not been any cases of recurrence or progression of MOM [11]. Simple excision, including excisional biopsy, is a suitable treatment of choice for MOM [6]. 2109
In conclusion, this is the 22nd reported case of MOM occurring in an Asian man who is a heavy smoker. Asian ethnicity and the history of heavy smoking are likely related to the development of MOM. In addition to 2 frequently used melanocytic markers, S-100 protein and HMB-45, 2 additional melanocytic markers with high specificity, Melan-A and MITF, were used in this case. The use of these additional markers increases the accuracy of the diagnosis, as S-100 is less specific as a marker for melanocytes and HMB-45, a more specific marker, hardly recognizes melanocytes not being stimulated. Some cells of MOM in this case were shown to stain positively for Melan-A and MITF, which indicated the definite presence of melanocytes. Using S-100 protein and HMB-45 alone would not be sufficient for evaluating benign and dormant melanocytic lesions. Since MOM pursues a benign course, it will be sufficient to follow up regularly with the patient to evaluate progression of the remaining 3 lesions that were not biopsied. Disclosure of conflict of interest None. Address correspondence to: Dr. Shogo Tajima, Department of Pathology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-0033, Japan. Tel: +81-35841-3341; Fax: +81-3-3815-8379; E-mail: [email protected]
References [1] [2] [3]
[4] [5]
[6]
Shek TW, Luk IS, Nicholls JM and Fok KO. Melanotic oncocytic metaplasia of the nasopharynx. Histopathology 1995; 26: 273-275. Kurihara K and Nakagawa K. Pigmented variant of benign oncocytic lesion of the pharynx. Pathol Int 1997; 47: 315-317. Hirakawa E, Miki H, Ohmori M, Kobayashi S, Haba R and Nagai Y. Melanin pigmented oncocytic metaplasia of the nasopharynx. Virchows Arch 1999; 434: 455-457. Xue WC and Hui YZ. Melanotic oncocytic metaplasia of the nasopharynx. Histopathology 1999; 35: 481-482. Sakaki M, Shek TW, Hirokawa M, Kashima K, Daa T, Gamachi A and Sano T. Melanotic oncocytic metaplasia of the nasopharynx: a report of seven cases and review of the literature. Virchows Arch 2004; 444: 345-349. Takano K, Sato J, Shirasaki H, Yamazaki N, Hoki K and Himi T. Melanin pigmented oncocytic metaplasia of the nasopharynx. Auris Nasus Larynx 2004; 31: 161-163.
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Nasopharyngeal melanotic oncocytic metaplasia [7]
[8] [9]
[10]
[11]
[12] [13] [14] [15]
Lui PC, Chan AB, Chan KF, Choi CH and Tse GM. Melanocytic and non-melanocytic oncocytic metaplasia of the nasopharynx. Pathology 2004; 36: 504-505. Liao CT and Kuo TT. Images in pathology. Melanotic oncocytic metaplasia of the nasopharynx. Int J Surg Pathol 2005; 13: 279. Kondo T, Mori K, Oka S and Morinaka S. Melanotic oncocytic metaplasia of the nasopharynx as a benign mimicker of malignant melanoma: a case report. Diagn Pathol 2010; 5: 5. Li Y, Lu ZH, Lu W and Chen J. Images for diagnosis. Melanotic oncocytic metaplasia of nasopharynx: a case report with review. Chin Med J (Engl) 2010; 123: 1230-1232. Na JY, Kim YH, Choi YD and Lee JS. Melanotic oncocytic metaplasia of the nasopharynx: a report of three cases and review of the literature. Korean J Pathol 2012; 46: 201-204. Chang IW, Wang CC, Liu KW, Lan CH and Hung CH. Melanotic oncocytic metaplasia of the nasopharynx. Pol J Pathol 2014; 65: 162-164. Morin GV, Shank EC, Burgess LP and Heffner DK. Oncocytic metaplasia of the pharynx. Otolaryngol Head Neck Surg 1991; 105: 86-91. Hartwick RW and Batsakis JG. Non-Warthin’s tumor oncocytic lesions. Ann Otol Rhinol Laryngol 1990; 99: 674-677. Hedin CA and Axell T. Oral melanin pigmentation in 467 Thai and Malaysian people with special emphasis on smoker’s melanosis. J Oral Pathol Med 1991; 20: 8-12.
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[16] Uehara T, Matsubara O and Kasuga T. Melanocytes in the nasal cavity and paranasal sinus. Incidence and distribution in Japan. Acta Pathol Jpn 1987; 37: 1105-1114. [17] Clarkson KS, Sturdgess IC and Molyneux AJ. The usefulness of tyrosinase in the immunohistochemical assessment of melanocytic lesions: a comparison of the novel T311 antibody (anti-tyrosinase) with S-100, HMB45, and A103 (anti-melan-A). J Clin Pathol 2001; 54: 196-200. [18] Smoller BR, McNutt NS and Hsu A. HMB-45 recognizes stimulated melanocytes. J Cutan Pathol 1989; 16: 49-53. [19] Fetsch PA, Fetsch JF, Marincola FM, Travis W, Batts KP and Abati A. Comparison of melanoma antigen recognized by T cells (MART-1) to HMB-45: additional evidence to support a common lineage for angiomyolipoma, lymphangiomyomatosis, and clear cell sugar tumor. Mod Pathol 1998; 11: 699-703. [20] Busam KJ and Jungbluth AA. Melan-A, a new melanocytic differentiation marker. Adv Anat Pathol 1999; 6: 12-18. [21] Widlund HR and Fisher DE. Microphthalamiaassociated transcription factor: a critical regulator of pigment cell development and survival. Oncogene 2003; 22: 3035-3041.
Int J Clin Exp Pathol 2015;8(2):2103-2110
Case Report Melanotic oncocytic metaplasia of the nasopharynx: a case report with a focus on immunohistochemical analyses and literature review Shogo Tajima1,2, Aki Ohkubo3, Matsumi Yoshida3, Kenji Koda2, Ichirota Nameki3 1 2
Department of Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Departments of Pathology, 3Otolaryngology, Fujieda Municipal General Hospital, Shizuoka, Japan
Received December 3, 2014; Accepted January 28, 2015; Epub February 1, 2015; Published February 15, 2015 Abstract: Melanotic oncocytic metaplasia (MOM) of the nasopharynx is an extremely rare lesion, with only 21 cases reported in English literature to date. MOM typically occurs near the Eustachian tube opening in Asian men in their 60 s to 70 s. Here, we present a case of MOM in a 57-year-old Japanese man who is a heavy smoker. The patient did not have complaints; MOM was diagnosed incidentally as 4 flat elevated lesions with brown to black discoloration, ranging from 2 to 3 mm in maximal diameter, were found in the right torus tubarius. On suspecting melanoma, the largest lesion was biopsied. Microscopic examination identified both oncocytic metaplasia and melanin pigmentation of the epithelium in the same gland. Upon immunohistochemical examination, melanocytes displayed reactivity for 3 out of 4 melanocytic markers; immunopositivity for S-100 protein, Melan-A, and MITF and immunonegativity for HMB-45 was observed. Normal melanocytes in the nearby surface respiratory epithelium displayed the same pattern of immunoreactivity. Immunopositivity for S-100 protein and immunonegativity for HMB-45 have been previously reported in MOM. Reduction of stimulation of melanocytes in a longstanding lesion like MOM may explain the immunonegativity for HMB-45. S-100 protein, in conjunction with more specific marker for melanocytes, Melan-A or MITF, could prove the definite presence of melanocytes in this case of MOM. As it has been shown by previous reports that MOM pursues a benign course, it will be sufficient to follow up the patients regularly for the remaining 3 lesions. Keywords: Melanotic oncocytic metaplasia, nasopharynx, immunohistochemistry
Introduction Melanotic oncocytic metaplasia (MOM) of the nasopharynx is an extremely rare lesion, first described by Shek et al. in 1995 [1]. There have been only 21 cases reported in English literature to date [1-12]. MOM has typically been diagnosed near the Eustachian tube opening in Asian men in their 60s to 70 s. MOM lesions are usually a few millimeters in size with a slight elevation and show brown to black discoloration. Multiple lesions and bilateral involvement have sometimes been encountered in patients [5]. The associated representative symptoms such as otitis media and tinnitus may be caused by compression of the Eustachian tube [11]. Although MOM may be macroscopically misidentified as early nasopharyngeal carcinoma,
malignant melanoma, or nevus, it is microscopically distinct from these three diseases; MOM is characterized by an admixture of both melanin pigmentation and oncocytic metaplasia in the same gland [9]. The source of melanin was attributable to the numerous melanocytes found to coexist in MOM. Upon immunohistochemical (IHC) analysis, the melanocytes were found to be positive for S-100 protein and negative for HMB-45, both of which are melanocytic markers; only one study on MOM tested for reactivity with Melan-A, another marker of melanocytes, and found a positive result [12]. In this study, we present an additional case of MOM, where the melanocytes stained positively for S-100 protein and negatively for HMB-45, as found by IHC analysis, as was expected. We further analyzed the immunoreactivity of the melanocytes for two additional melanocytic
Nasopharyngeal melanotic oncocytic metaplasia
Figure 1. Laryngoscopical examination revealed lesions in the right torus tubarius. (A) One of the 4 flat elevated lesions found in the right torus tubarius. It displayed brown to black discoloration and ranged from 2 to 3 mm in maximal diameter. (B) (A) in higher magnification.
markers, Melan-A and MITF, and found that the cell showed positive staining for both the markers. This pattern of expression signature of melanocytes in MOM is discussed in this report and extensive review of the literature was conducted to extract characteristics of MOM. Clinical findings A 57-year-old Japanese man, who was regularly followed up and treated at a local clinic for hypertension and hyperlipidemia, was referred because of elevated carcinoembryonic antigen (CEA: 8.9 ng/ml; normal range: < 5 ng/ml) levels and a positive result for fecal occult blood test. He is a heavy smoker with a history of smoking 30 cigarettes per day for the past 40 years (Brinkman index: 1200). Upper and lower endoscopic examination revealed no abnormality. By computed tomography (CT), several nodules with central cavities in the bilateral lung were identified. Metastatic or inflammatory lesions were suspected, but the patient refused a TBLB. The head and neck region was examined to search for the origin of a possible metastatic tumor. No palpable mass was found in this region. The patient underwent laryngoscopy, and 4 flat, elevated lesions with brown to black discoloration, ranging from 2 to 3 mm in the maximal diameter, were found in the right torus tubarius (Figure 1A, 1B). Melanoma was 2104
suspected, and a biopsy was collected from the largest lesion; examination revealed MOM. Examination of the nasal cavity, pharynx, and larynx revealed no additional lesions. Subsequently, fluorodeoxyglucose positron emission tomography was performed. No abnormal accumulation was found in the lung or any other organs. Six months later, the patient was reexamined by CT. The lesions that had been initially detected had disappeared and were therefore considered inflammatory lesions. However, the patient’s CEA level was still elevated (6.2 ng/ml); the increased CEA level was suspected to be a result of heavy smoking. As the lesions of the right torus tubarius were not enlarged, he was referred back to the local clinic. Pathological findings The biopsied tissue was fixed in 10% buffered formalin. The specimen was then embedded in paraffin. Sections were cut for hematoxylin and eosin (H&E) staining (2.5 μm thick sections), Fontana-Masson staining (2.5 μm thick sections), and immunohistochemical analysis (IHC; 4 μm thick sections). IHC analysis was performed using an automated slide stainer (Bench-Mark GX; Ventana Medical Systems, Tucson, AZ, USA). Giemsa staining was used as a counterstain for the specimen used for IHC analysis. Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia
Figure 2. Histopathological findings. A. The surface of the lesion was covered by respiratory epithelium with goblet cells. It was composed of pre-existing seromucous glands with diffuse oncocytic metaplasia (× 20). B. Oncocytes presented abundant eosinophilc granular cytoplasm. Brown pigments were also observed in the cytoplasm of many
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Nasopharyngeal melanotic oncocytic metaplasia oncocytes (× 200). C. Upon closer inspection, melanocytes were hardly discernible. Mitotic figures or atypia of oncocytes were not observed. The pigments stained positive with Fontana-Masson staining (inset) (× 400).
Figure 3. Immunohistochemistry of the lesion. Giemsa staining used as a counterstain revealed metachromasia for melanin pigment. Arrows indicate melanocytes. A. Melanocytes stained positive for S-100 protein (× 400). B. Melanocytes stained negative for HMB-45 (× 400). C. Melanocytes were immunoreactive for Melan-A (× 400). D. Melanocytes were immunopositive for MITF (× 400).
Microscopically, the lesion was well demarcated, but was not encapsulated. The surface was covered by respiratory epithelium with goblet cells. The lesion was composed of pre-existing seromucous glands with diffuse oncocytic metaplasia (Figure 2A). Oncocytes presented abundant eosinophilic granular cytoplasm. Brown pigments were also observed in the cytoplasm of many oncocytes (Figure 2B). Upon closer inspection, melanocytes were found to be hardly discernible. Mitotic figures or atypia of oncocytes were not observed (Figure 2C). The brown pigments were positive for Fontana-Masson staining 2106
(Figure 2C, inset), indicating melanin or lipofuscin. IHC analysis revealed melanocytes in the basal layer and intervening glandular cells. The melanocytes were positive for S-100 protein (polyclonal, 1:1000; Dako, Glostrup, Denmark) (Figure 3A). HMB-45 did not show immunoreactivity (HMB-45, 1:100; Dako) (Figure 3B). The melanocytes were found to be immunoreactive to Melan-A (A103, 1:50; Dako) (Figure 3C) and MITF (D5, 1:100; Dako) (Figure 3D). Melanocytes also existed in the surface respiratory epithelium near the lesion, which showed the Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia
Figure 4. Immunohistochemistry of the surface respiratory epithelium. Giemsa staining revealed metachromasia for melanin pigment. A. Melanocytes stained positive for S-100 protein (× 400). B. Melanocytes were negative for HMB-45 staining (× 400). C. Melanocytes were positive for Melan-A staining (× 400). D. Melanocytes were positive for MITF staining (× 400).
same staining pattern on IHC for the 4 antibodies (Figure 4A-D). As a counterstain of IHC, Giemsa staining was performed and displayed metachromasia, where the color of pigments changed from brown to green. This phenomenon was observed in all IHC specimens. This observation, together with the positive FontanaMasson staining, demonstrated that the pigments were indeed melanin. The diagnosis of MOM was rendered, supported by the result of H&E staining, special staining, and IHC analysis, along with the results of macroscopic observations. Discussion This case of the extremely rare lesion, MOM, is the 22nd reported case (Table 1) [1-12]. MOM 2107
comprises both oncocytic metaplasia and melanin pigmentation of the epithelium in the same gland. Oncocytic metaplasia of the glandular epithelium alone is sometimes encountered, which is considered an age-related phenomenon in the nasopharynx [13] and is common in the salivary gland [14]. Because oncocytic metaplasia is more frequently encountered than melanin pigmentation in the nasopharynx, it is speculated that melanin pigmentation occurred after oncocytic metaplasia. It has also been suggested that smoking may be a predisposing factor for melanin pigmentation. This speculation is supported by the observed relationship between oral melanin pigmentation and smoking in some Asian populations [15]. Male predominance can be explained by the fact that there are more male than female smokers among Asians [5]. Int J Clin Exp Pathol 2015;8(2):2103-2110
Nasopharyngeal melanotic oncocytic metaplasia Table 1. Cases of melanotic oncocytic metaplasia of the nasopharynx Case
Author
Year
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Shek et al. [1] Shek et al. [1] Kurihara et al. [2] Hirakawa et al. [3] Xue et al. [4] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Sakaki et al. [5] Takano et al. [6] Lui et al. [7] Liao et al. [8] Kondo et al. [9] Li et al. [10] Na et al. [11]
1995 1995 1997 1999 1999 2004 2004 2004 2004 2004 2004 2004 2004 2004 2005 2010 2010 2012
19 20 21 22
Na et al. [11] Na et al. [11] Chang et al. [12] Present case
2012 2012 2014 2014
Gender/ Number Site Symptom Age of lesions M/67 Single Eustachian opening Otitis media M/63 Single Eustachian opening Tinnitus M/69 Multiple Left nasopharynx None M/64 Multiple Bilateral Eustachian opening, left pharynx, and nasal cavity Discomfort in the throat M/70 Multiple Bilateral Eustachian opening Tinnitus M/80 Multiple Right nasal cavity and pharynx Hoarseness M/69 Single Left Eustachian opening Hoarseness M/74 Single Left nasopharynx Rhinorrhea F/74 Multiple Right Eustachian opening Discomfort in the throat M/68 Single Nasopharynx None M/65 Single Right Eustachian opening Hemoptysis M/63 Single Left Eustachian opening Epistaxis M/62 Multiple Left Eustachian opening, and bilateral torus tubarius Discomfort in the left ear M/79 Single Right Eustachian opening Otitis media M/Multiple Bilateral nasopharynx None M/73 Multiple Bilateral torus tubarius Nasal congestion M/58 Multiple Bilateral nasopharynx Epistaxis M/72 Multiple Bilateral torus tubarius Headache and impaired hearing M/71 Multiple Left torus tubarius and soft palate Hoarseness M/51 Multiple Right torus tubarius Pain of the tongue M/63 Multiple Nasopharynx Epistaxis M/57 Multiple Right torus tubarius None
Smoking history Unknown Unknown Unknown Unknown Unknown 10/day × 50 yr 40/day × 60 yr Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Non-smoker 20/day × 40 yr 40/day × 50 yr 20/day × 40 yr Unknown 40/day × 40 yr 30/day × 40 yr
M, male; F, female; yr, year.
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Nasopharyngeal melanotic oncocytic metaplasia Melanocytes are consistently present in MOM as a source for melanin pigmentation in oncocytes [1-12]. Melanocytes have been reported to exist in the epithelium and stroma of the nasal cavity [16] and are postulated to colonize in MOM. Ultrastructurally, oncocytes in MOM lack premature melanosomes, in which melanin is produced [3]. Hence, the melanin pigment in MOM is believed to be passed on from the adjacent melanocytes via their dendrites [3]. Upon IHC examination of previous reports, there were some cells in MOM consistently found to be positive for S-100 protein and negative for HMB-45, both of which are melanocytic markers. Only one previous study confirmed the presence of melanocytes in MOM using a third melanocytic marker, Melan-A [12]. As S-100 protein is the most sensitive marker for melanocytes [17], positive staining for S-100 was expected. However, positive staining for S-100 protein does not conclusively identify cells as melanocytes due to its lack of specificity [17]. Although HMB-45 is a more specific marker for melanocytes than S-100 protein [17], it stains premelanosome glycoprotein abundant in adult melanocytes during stimulation and normal adult skin melanocytes are not stained [18]. This is a likely explanation for why HMB-45 staining was not observed in previous studies. It may also be presumed that melanocytes in MOM are not in a highly stimulated state at the time of biopsy, indicating a previously developed and longstanding nature of MOM. In contrast, we speculate that melanocytes were stimulated during MOM development, judging by the abundant melanin pigmentation. Another melanocytic marker, Melan-A, which is the same as MART-1, a transmembrane protein of melanocytes [19], is more sensitive than HMB-45 [20]. Melan-A/MART-1 stains normal skin melanocytes [19], explaining the positive staining of melanocytes in MOM for Melan-A. MITF is an integral transcriptional regulator in melanocytes and expression of this gene is required [21]. This fact may explain the finding that melanocytes in MOM are positive for MITF. All the reported cases of MOM followed a benign clinical course; there have not been any cases of recurrence or progression of MOM [11]. Simple excision, including excisional biopsy, is a suitable treatment of choice for MOM [6]. 2109
In conclusion, this is the 22nd reported case of MOM occurring in an Asian man who is a heavy smoker. Asian ethnicity and the history of heavy smoking are likely related to the development of MOM. In addition to 2 frequently used melanocytic markers, S-100 protein and HMB-45, 2 additional melanocytic markers with high specificity, Melan-A and MITF, were used in this case. The use of these additional markers increases the accuracy of the diagnosis, as S-100 is less specific as a marker for melanocytes and HMB-45, a more specific marker, hardly recognizes melanocytes not being stimulated. Some cells of MOM in this case were shown to stain positively for Melan-A and MITF, which indicated the definite presence of melanocytes. Using S-100 protein and HMB-45 alone would not be sufficient for evaluating benign and dormant melanocytic lesions. Since MOM pursues a benign course, it will be sufficient to follow up regularly with the patient to evaluate progression of the remaining 3 lesions that were not biopsied. Disclosure of conflict of interest None. Address correspondence to: Dr. Shogo Tajima, Department of Pathology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-0033, Japan. Tel: +81-35841-3341; Fax: +81-3-3815-8379; E-mail: [email protected]
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