BRIEF REPORT
Loss of Conventional Melanocytic Markers in Malignant Melanoma and Lymph Node Metastasis; an Uncommon but Dangerous Pitfall Oliver Chang, MD,*† and Zsolt Argenyi, MD*
Abstract: Although malignant melanomas exhibit a wide range of immunophenotypes, concurrent loss of all 3 conventional melanocytic markers (S-100, Melan-A, and HMB-45) is relatively rare. We report a case of primary malignant melanoma with lymph node metastasis, both exhibiting loss of immunoreactivity for conventional melanocytic markers, while aberrantly expressing epithelial antigenicity (pancytokeratin, CAM 5.2). Key Words: malignant melanoma, immunohistochemistry, markernegative, cytokeratin expression (Am J Dermatopathol 2017;39:760–763)
INTRODUCTION Because of the morphologic and immunophenotypic heterogeneity of malignant melanoma (MM), a number of immunostains play important roles in distinguishing this neoplasm. Conventional melanocytic immunohistochemical stains include S-100, Melan-A, and HMB-45; an extended battery (eg, tyrosinase, microphthalmia transcription factor, and PNL2) may be used in cases with atypical cytomorphologic features or equivocal expression of conventional markers. MM may exhibit a wide range of immunoprofiles, ranging from loss of expression of conventional melanocytic markers,1 to aberrant antigen expression of other cell lineages (eg, epithelial, smooth muscle).2,3 Antigen expression may even evolve during the natural course of the disease, the most common alteration being loss of conventional melanocytic marker expression in metastatic lesions.4 The following case illustrates a conventional marker-negative MM and lymph node metastasis with a shared aberrant immunoprofile lacking several melanocytic markers while exhibiting certain epithelial markers.
CASE REPORT A 58-year-old man with no personal history of malignancy presented with a growing and bleeding low back lesion, biopsied to reveal MM (Fig. 1A). The subsequent excisional specimen contained a markedly atypical compound melanocytic neoplasm with a Breslow From the *Department of Anatomic Pathology, University of Washington Medical Center, Seattle, WA; and †Department of Anatomic Pathology, VA Puget Sound Health Care System, Seattle, WA. The authors declare no conflicts of interest. Reprints: Oliver Chang, MD, Anatomic Pathology and Dermatopathology, VA Puget Sound Health Care System, Seattle, WA 98108 (e-mail: [email protected]). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
760
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thickness of 4.75 mm, epidermal ulceration, and high mitotic index (9/mm2) (Fig. 1B). The architectural arrangement comprised an in situ component (Fig. 1C) on either side of a large, sheet-like/nodular central growth within the dermis. Routine immunohistochemical evaluation revealed some unexpected findings. Although nests along the peripheral aspect of the lesion exhibited strong and diffuse immunoreactivity for melanocytic markers (S-100, Melan-A, HMB-45, PNL2), the central viable dermal component was essentially devoid of immunoreactivity for the same melanocytic immunostains (Figs. 2A–D). Furthermore, these cells exhibited strong positivity in a vaguely nodular pattern for epithelial markers pancytokeratin and CAM 5.2 (Figs. 2E, F). Other markers for squamous cell carcinoma, prostate, lung, gastrointestinal tract, and hematopoietic neoplasms were negative (CK7, CK20, HMWCK, p63, PSA, TTF-1, Napsin-A, CDX-2, OCT3/4, CD3, CD20, and CD30). The accompanying sentinel lymph node was largely replaced by an expansive neoplastic proliferation with similar cytomorphology to the cutaneous melanoma (Fig. 3A). This population carried a similar immunoprofile with the absence of immunostaining for melanocytic markers (Fig. 3B), and positive with pancytokeratin and CAM 5.2 immunoreactivity (Figs. 3C, D). Other immunomarker expression within the lymph node metastasis included PAX-8 (also seen in the excision specimen, but not the original biopsy), GATA-3 (variable), and EMA (rare cells). Several months after interferon-a therapy and negative surveillance imaging, he was discovered to have a subcutaneous lesion within his right lateral hip. The excision contained a malignant neoplasm immunoreactive with pancytokeratin, CAM 5.2, and PAX-8; lesional cells were immunonegative for S-100 and Melan-A. These findings were originally interpreted as a “poorly differentiated carcinoma extending into the subcutis.” An outside consult raised the possibility of renal cell carcinoma, based on PAX-8 immunoreactivity; however, no renal primary was evident on imaging studies. Further immunohistochemical studies revealed expression of melanocytic marker SOX-10 (positive in original biopsy and regions of the excisional specimen with scattered positivity within the lymph node metastasis). Because of the similar immunophenotype as the primary melanoma and with immunohistochemical evidence of melanocytic differentiation, the hip lesion was interpreted to represent metastatic melanoma.
DISCUSSION There are many potential confounders that can hinder definitive diagnosis of MM on histopathology alone. MM is well known for carrying features that overlap with malignancies in epithelial and mesenchymal lineages, as well as non-neoplastic entities, for example, hypertrophic scar. In these cases, immunohistochemistry for conventional melanocytic markers (S-100, Melan-A, HMB-45) can provide Am J Dermatopathol Volume 39, Number 10, October 2017
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 39, Number 10, October 2017
Loss of Conventional Melanocytic Markers
FIGURE 1. A, Low back melanoma with epidermal ulceration and a sheet-like/nodular growth. (hematoxylin and eosin, ·4 magnification); inset: strong, diffuse SOX-10 immunoreactivity. B, High-power view of the malignant population, exhibiting enlarged, pleomorphic cells with increased N:C and high mitotic index (·4 magnification); inset: pleomorphic cells with several mitotic figures (·60 magnification). C, melanoma in situ at the peripheral of the lesion (hematoxylin and eosin, ·10 magnification); inset: Melan-A red immunostaining highlighting in situ melanoma (·10 magnification).
antigenic evidence of melanocytic differentiation. Of these markers, S-100 is the most sensitive, often retained when other marker expression is lost, as seen in spindle cell and Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
desmoplastic melanomas5; however, melanomas of various histopathologic profiles may exhibit loss of S-100 expression as well.6 Triple-antigen negative melanomas are www.amjdermatopathology.com |
761
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Chang and Argenyi
Am J Dermatopathol Volume 39, Number 10, October 2017
FIGURE 2. Scattered nodules toward the peripheral aspect of the central nodule highlighted by S-100 (A), Melan-A (B), HMB-45 (C), and PNL2 (D). The central sheet-like portion is predominantly negative for the aforementioned melanocytic markers, and instead expressed epithelial antigens pancytokeratin (E) and CAM 5.2 (F). ·4 magnification.
exceedingly rare, representing only 1 of 322 assayed melanomas in one study.6 S-100-negative metastatic melanomas are well reported,7 with the loss of expression being loosely associated with conferral of metastatic potential. This is evidenced by many cases having S-100-positive primaries.8 Analysis of more than 1500 metastatic melanomas showed the time interval of S-100 loss ranging from 3 weeks to 3 years.7 It is unknown how long the patient carried the primary lesion, but we hypothesize the primary lesion lost S-100 expression before metastasizing, thereby explaining the matching immunoprofile of the metastatic focus. An alternate hypothesis is poor fixation within the central component of the excision specimen; however, this seems
unlikely given the loss of markers within the concurrent sentinel lymph node metastasis. Comparative genomic hybridization on an S-100positive primary melanoma and its associated S-100-negative metastasis revealed that metastatic cells carry identical cytogenetic changes to the primary lesion, but with additional copy number gains and losses, including the Melan-A encoding gene.9 Instances of metastases positive for melanoma markers that were absent in the primaries have been reported as well.10,11 In addition to loss of melanocytic marker expression, MM may aberrantly express nonmelanocytic antigens. Of the 106 surveilled melanomas, 7% exhibited CAM 5.2 positivity with loss of S-100, HMB-45, and NKI/C3
762
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
| www.amjdermatopathology.com
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 39, Number 10, October 2017
Loss of Conventional Melanocytic Markers
FIGURE 3. A, Sentinel lymph nodes involved by metastatic disease with similar cytomorphology as the primary cutaneous lesion (hematoxylin and eosin, ·4 magnification). B (clockwise from upper left: S-100, Melan-A, HMB-45, SOX-10), As with the primary lesion, the metastatic focus was largely devoid of melanocytic markers, except for scattered positive nuclei for SOX-10, and expressed epithelial antigens pancytokeratin (C; ·10 magnification) and CAM 5.2 (D; ·10 magnification).
expression.8 Actin-rich variants have also been documented, as well as expression of CD34 and epithelial membrane antigen.4 Our particular case represents an unusual combination of almost total loss of conventional melanocytic immunomarker expression, along with the acquisition of cytokeratin expression (pancytokeratin and CAM 5.2). In these cases, one may benefit from other—less often used—markers of melanocytic development (eg, MITF, SOX-9).12,13 Even with constant reinforcement of the incredible variety of clinical and pathologic presentations of MM, this report serves as a reminder to not underestimate the capriciousness of this entity, especially if the lesion is not fully represented in the biopsy. It is therefore prudent, especially under circumstances with strong clinical suspicion, to use a wide battery of melanocytic markers in an effort to avoid misdiagnosing a melanoma with an unusual immunophenotype. REFERENCES 1. Shinohara MM, Deubner H, Argenyi ZB. S100, HMB-45, and Melan-A negative primary melanoma. Dermatol Online J. 2009;15:7. 2. Banerjee SS, Eyden B. Divergent differentiation in malignant melanomas: a review. Histopathology. 2008;52:119–129. 3. Magro CM, Crowson AN, Mihm MC. Unusual variants of malignant melanoma. Mod Pathol. 2006;19(suppl 2):S41–S70.
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
4. Trefzer U, Hofmann M, Reinke S, et al. Concordant loss of melanoma differentiation antigens in synchronous and asynchronous melanoma metastases: implications for immunotherapy. Melanoma Res. 2006;16: 137–145. 5. Ohsie SJ, Sarantopoulos GP, Cochran AJ, et al. Immunohistochemical characteristics of melanoma. J Cutan Pathol. 2008;35:433–444. 6. Viray H, Bradley WR, Schalper KA, et al. Marginal and joint distributions of S100, HMB-45, and Melan-A across a large series of cutaneous melanomas. Arch Pathol Lab Med. 2013;137:1063–1073. 7. Aisner DL, Maker A, Rosenberg SA, et al. Loss of S100 antigenicity in metastatic melanoma. Hum Pathol. 2005;36:1016–1019. 8. Bishop PW, Menasce LP, Yates AJ, et al. An immunophenotypic survey of malignant melanomas. Histopathology. 1993;23:159–166. 9. Guo R, Wang X, Chen J, et al. Comparative genomic hybridization in a case of melanoma that loses expression of S100, HMB45, Melan A and tyrosinase in metastasis. Int J Clin Exp Pathol. 2014;7:468–473. 10. Argenyi ZB, Cain C, Bromley C, et al. S-100 protein-negative malignant melanoma: fact or fiction? A light-microscopic and immunohistochemical study. Am J Dermatopathol. 1994;16:233–240. 11. Sheth A, Arsenovic N. Melanoma markers-negative primary melanoma with melanoma markers-positive metastasis. Int J Surg Pathol. 2011;19: 127–130. 12. Guo R, Franco-palacios M, Russell M, et al. Micropthalmia transcription factor (MITF) as a diagnostic marker for metastatic melanomas negative for other melanoma markers. Int J Clin Exp Pathol. 2013;6:1658–1664. 13. Rao P, Fuller GN, Prieto VG. Expression of Sox-9 in metastatic melanoma— a potential diagnostic pitfall. Am J Dermatopathol. 2010;32:262–266.
www.amjdermatopathology.com |
763
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Loss of Conventional Melanocytic Markers in Malignant Melanoma and Lymph Node Metastasis; an Uncommon but Dangerous Pitfall Oliver Chang, MD,*† and Zsolt Argenyi, MD*
Abstract: Although malignant melanomas exhibit a wide range of immunophenotypes, concurrent loss of all 3 conventional melanocytic markers (S-100, Melan-A, and HMB-45) is relatively rare. We report a case of primary malignant melanoma with lymph node metastasis, both exhibiting loss of immunoreactivity for conventional melanocytic markers, while aberrantly expressing epithelial antigenicity (pancytokeratin, CAM 5.2). Key Words: malignant melanoma, immunohistochemistry, markernegative, cytokeratin expression (Am J Dermatopathol 2017;39:760–763)
INTRODUCTION Because of the morphologic and immunophenotypic heterogeneity of malignant melanoma (MM), a number of immunostains play important roles in distinguishing this neoplasm. Conventional melanocytic immunohistochemical stains include S-100, Melan-A, and HMB-45; an extended battery (eg, tyrosinase, microphthalmia transcription factor, and PNL2) may be used in cases with atypical cytomorphologic features or equivocal expression of conventional markers. MM may exhibit a wide range of immunoprofiles, ranging from loss of expression of conventional melanocytic markers,1 to aberrant antigen expression of other cell lineages (eg, epithelial, smooth muscle).2,3 Antigen expression may even evolve during the natural course of the disease, the most common alteration being loss of conventional melanocytic marker expression in metastatic lesions.4 The following case illustrates a conventional marker-negative MM and lymph node metastasis with a shared aberrant immunoprofile lacking several melanocytic markers while exhibiting certain epithelial markers.
CASE REPORT A 58-year-old man with no personal history of malignancy presented with a growing and bleeding low back lesion, biopsied to reveal MM (Fig. 1A). The subsequent excisional specimen contained a markedly atypical compound melanocytic neoplasm with a Breslow From the *Department of Anatomic Pathology, University of Washington Medical Center, Seattle, WA; and †Department of Anatomic Pathology, VA Puget Sound Health Care System, Seattle, WA. The authors declare no conflicts of interest. Reprints: Oliver Chang, MD, Anatomic Pathology and Dermatopathology, VA Puget Sound Health Care System, Seattle, WA 98108 (e-mail: [email protected]). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
760
| www.amjdermatopathology.com
thickness of 4.75 mm, epidermal ulceration, and high mitotic index (9/mm2) (Fig. 1B). The architectural arrangement comprised an in situ component (Fig. 1C) on either side of a large, sheet-like/nodular central growth within the dermis. Routine immunohistochemical evaluation revealed some unexpected findings. Although nests along the peripheral aspect of the lesion exhibited strong and diffuse immunoreactivity for melanocytic markers (S-100, Melan-A, HMB-45, PNL2), the central viable dermal component was essentially devoid of immunoreactivity for the same melanocytic immunostains (Figs. 2A–D). Furthermore, these cells exhibited strong positivity in a vaguely nodular pattern for epithelial markers pancytokeratin and CAM 5.2 (Figs. 2E, F). Other markers for squamous cell carcinoma, prostate, lung, gastrointestinal tract, and hematopoietic neoplasms were negative (CK7, CK20, HMWCK, p63, PSA, TTF-1, Napsin-A, CDX-2, OCT3/4, CD3, CD20, and CD30). The accompanying sentinel lymph node was largely replaced by an expansive neoplastic proliferation with similar cytomorphology to the cutaneous melanoma (Fig. 3A). This population carried a similar immunoprofile with the absence of immunostaining for melanocytic markers (Fig. 3B), and positive with pancytokeratin and CAM 5.2 immunoreactivity (Figs. 3C, D). Other immunomarker expression within the lymph node metastasis included PAX-8 (also seen in the excision specimen, but not the original biopsy), GATA-3 (variable), and EMA (rare cells). Several months after interferon-a therapy and negative surveillance imaging, he was discovered to have a subcutaneous lesion within his right lateral hip. The excision contained a malignant neoplasm immunoreactive with pancytokeratin, CAM 5.2, and PAX-8; lesional cells were immunonegative for S-100 and Melan-A. These findings were originally interpreted as a “poorly differentiated carcinoma extending into the subcutis.” An outside consult raised the possibility of renal cell carcinoma, based on PAX-8 immunoreactivity; however, no renal primary was evident on imaging studies. Further immunohistochemical studies revealed expression of melanocytic marker SOX-10 (positive in original biopsy and regions of the excisional specimen with scattered positivity within the lymph node metastasis). Because of the similar immunophenotype as the primary melanoma and with immunohistochemical evidence of melanocytic differentiation, the hip lesion was interpreted to represent metastatic melanoma.
DISCUSSION There are many potential confounders that can hinder definitive diagnosis of MM on histopathology alone. MM is well known for carrying features that overlap with malignancies in epithelial and mesenchymal lineages, as well as non-neoplastic entities, for example, hypertrophic scar. In these cases, immunohistochemistry for conventional melanocytic markers (S-100, Melan-A, HMB-45) can provide Am J Dermatopathol Volume 39, Number 10, October 2017
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 39, Number 10, October 2017
Loss of Conventional Melanocytic Markers
FIGURE 1. A, Low back melanoma with epidermal ulceration and a sheet-like/nodular growth. (hematoxylin and eosin, ·4 magnification); inset: strong, diffuse SOX-10 immunoreactivity. B, High-power view of the malignant population, exhibiting enlarged, pleomorphic cells with increased N:C and high mitotic index (·4 magnification); inset: pleomorphic cells with several mitotic figures (·60 magnification). C, melanoma in situ at the peripheral of the lesion (hematoxylin and eosin, ·10 magnification); inset: Melan-A red immunostaining highlighting in situ melanoma (·10 magnification).
antigenic evidence of melanocytic differentiation. Of these markers, S-100 is the most sensitive, often retained when other marker expression is lost, as seen in spindle cell and Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
desmoplastic melanomas5; however, melanomas of various histopathologic profiles may exhibit loss of S-100 expression as well.6 Triple-antigen negative melanomas are www.amjdermatopathology.com |
761
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Chang and Argenyi
Am J Dermatopathol Volume 39, Number 10, October 2017
FIGURE 2. Scattered nodules toward the peripheral aspect of the central nodule highlighted by S-100 (A), Melan-A (B), HMB-45 (C), and PNL2 (D). The central sheet-like portion is predominantly negative for the aforementioned melanocytic markers, and instead expressed epithelial antigens pancytokeratin (E) and CAM 5.2 (F). ·4 magnification.
exceedingly rare, representing only 1 of 322 assayed melanomas in one study.6 S-100-negative metastatic melanomas are well reported,7 with the loss of expression being loosely associated with conferral of metastatic potential. This is evidenced by many cases having S-100-positive primaries.8 Analysis of more than 1500 metastatic melanomas showed the time interval of S-100 loss ranging from 3 weeks to 3 years.7 It is unknown how long the patient carried the primary lesion, but we hypothesize the primary lesion lost S-100 expression before metastasizing, thereby explaining the matching immunoprofile of the metastatic focus. An alternate hypothesis is poor fixation within the central component of the excision specimen; however, this seems
unlikely given the loss of markers within the concurrent sentinel lymph node metastasis. Comparative genomic hybridization on an S-100positive primary melanoma and its associated S-100-negative metastasis revealed that metastatic cells carry identical cytogenetic changes to the primary lesion, but with additional copy number gains and losses, including the Melan-A encoding gene.9 Instances of metastases positive for melanoma markers that were absent in the primaries have been reported as well.10,11 In addition to loss of melanocytic marker expression, MM may aberrantly express nonmelanocytic antigens. Of the 106 surveilled melanomas, 7% exhibited CAM 5.2 positivity with loss of S-100, HMB-45, and NKI/C3
762
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
| www.amjdermatopathology.com
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Am J Dermatopathol Volume 39, Number 10, October 2017
Loss of Conventional Melanocytic Markers
FIGURE 3. A, Sentinel lymph nodes involved by metastatic disease with similar cytomorphology as the primary cutaneous lesion (hematoxylin and eosin, ·4 magnification). B (clockwise from upper left: S-100, Melan-A, HMB-45, SOX-10), As with the primary lesion, the metastatic focus was largely devoid of melanocytic markers, except for scattered positive nuclei for SOX-10, and expressed epithelial antigens pancytokeratin (C; ·10 magnification) and CAM 5.2 (D; ·10 magnification).
expression.8 Actin-rich variants have also been documented, as well as expression of CD34 and epithelial membrane antigen.4 Our particular case represents an unusual combination of almost total loss of conventional melanocytic immunomarker expression, along with the acquisition of cytokeratin expression (pancytokeratin and CAM 5.2). In these cases, one may benefit from other—less often used—markers of melanocytic development (eg, MITF, SOX-9).12,13 Even with constant reinforcement of the incredible variety of clinical and pathologic presentations of MM, this report serves as a reminder to not underestimate the capriciousness of this entity, especially if the lesion is not fully represented in the biopsy. It is therefore prudent, especially under circumstances with strong clinical suspicion, to use a wide battery of melanocytic markers in an effort to avoid misdiagnosing a melanoma with an unusual immunophenotype. REFERENCES 1. Shinohara MM, Deubner H, Argenyi ZB. S100, HMB-45, and Melan-A negative primary melanoma. Dermatol Online J. 2009;15:7. 2. Banerjee SS, Eyden B. Divergent differentiation in malignant melanomas: a review. Histopathology. 2008;52:119–129. 3. Magro CM, Crowson AN, Mihm MC. Unusual variants of malignant melanoma. Mod Pathol. 2006;19(suppl 2):S41–S70.
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
4. Trefzer U, Hofmann M, Reinke S, et al. Concordant loss of melanoma differentiation antigens in synchronous and asynchronous melanoma metastases: implications for immunotherapy. Melanoma Res. 2006;16: 137–145. 5. Ohsie SJ, Sarantopoulos GP, Cochran AJ, et al. Immunohistochemical characteristics of melanoma. J Cutan Pathol. 2008;35:433–444. 6. Viray H, Bradley WR, Schalper KA, et al. Marginal and joint distributions of S100, HMB-45, and Melan-A across a large series of cutaneous melanomas. Arch Pathol Lab Med. 2013;137:1063–1073. 7. Aisner DL, Maker A, Rosenberg SA, et al. Loss of S100 antigenicity in metastatic melanoma. Hum Pathol. 2005;36:1016–1019. 8. Bishop PW, Menasce LP, Yates AJ, et al. An immunophenotypic survey of malignant melanomas. Histopathology. 1993;23:159–166. 9. Guo R, Wang X, Chen J, et al. Comparative genomic hybridization in a case of melanoma that loses expression of S100, HMB45, Melan A and tyrosinase in metastasis. Int J Clin Exp Pathol. 2014;7:468–473. 10. Argenyi ZB, Cain C, Bromley C, et al. S-100 protein-negative malignant melanoma: fact or fiction? A light-microscopic and immunohistochemical study. Am J Dermatopathol. 1994;16:233–240. 11. Sheth A, Arsenovic N. Melanoma markers-negative primary melanoma with melanoma markers-positive metastasis. Int J Surg Pathol. 2011;19: 127–130. 12. Guo R, Franco-palacios M, Russell M, et al. Micropthalmia transcription factor (MITF) as a diagnostic marker for metastatic melanomas negative for other melanoma markers. Int J Clin Exp Pathol. 2013;6:1658–1664. 13. Rao P, Fuller GN, Prieto VG. Expression of Sox-9 in metastatic melanoma— a potential diagnostic pitfall. Am J Dermatopathol. 2010;32:262–266.
www.amjdermatopathology.com |
763
Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
