YOSHIMURA
J Oral Maxillofac
1231
AND SAITO
Surg
48:1231-1235.1990
Desmoplastic
Variant of Ameloblastoma:
Report of a Case and Review of the Literature YASURO YOSHIMURA,
DDS, PHD,* AND HISAAKI SAITO, DDSt
Ameloblastomas are among the most common odontogenic tumors, generally occurring in the jaws, but rarely in other parts of the body.‘” They appear as bone swellings, cystic lesions, and softtissue tumors that at times become very large.lm3 Although they may occasionally be diagnosed clinically from their appearance and radiographic features, the final diagnosis depends on the histopathologic findings obtained from biopsied or surgically excised tissue specimens.4 Before the findings of Eversole et a1,3*5classifications based on the histologic features of ameloblastoma generally included the follicular, plexiform, squamous metaplastic, granular cell, basal cell, hemangiomatous, and unicystic types. ’ However, recently a new and unusual variant has been added, the histologic features of which are characterized by marked stromal desmoplastic proliferation. ‘*4 The incidence of follicular and plexiform ameloblastoma is relatively high, whereas desmoplastic
FIGURE process.
1. Intraoral view showing expansion of the alveolar
Received from the Department of Oral and Maxillofacial Surgery, Shimane Medical University, Shimane, Japan. * Professor. t Instructor. Address correspondence and reprint requests to Dr Yoshimura: 89-1, Enya chb, Izumo City, Shimane, Japan (693). 0 1990 geons
American
0278-2391/90/481
Association l-0020$3.00/0
of Oral
and Maxillofacial
Sur-
FIGURE 2. A, Occlusal view showing small multilocular spaces and wide divergence of the lateral incisor and canine tooth. B, Axial CT showing a mass with an ill-defined boundary and a slightly higher density than that of the adjacent soft tissue invading the left maxillary sinus and hard palate. Various-sized high-density masses are visible at the periphery.
1232
DESMOPLASTIC
VARIANT OF AMELOBLASTOMA
FIGURE 3. A, Photomicrograph showing odontogenic epithelial islands scattered throughout the abundant desmoplastic stroma (original magnification x40). B, Photomicrograph showing an odontogenic epithelial island in which the peripheral layer is formed by ameloblastlike cells (original magnification x200). C, Photomicrograph showing odontogenic epithelial island without ameloblastic cellular polarization. Central hypercellularity, squamous in nature, can be observed (original magnification X200). D. Photomicrograph showing myxoid changes in the stroma. Also note cystic islands (original magnification x 100).
ameloblastoma occurs infrequently. Hence, the uninitiated pathologist may fail to recognize and diagnose the latter accurately, especially when the specimen consists of only a small amount of biopsied material. This article describes a case of desmoplastic variant of ameloblastoma that occurred in the left maxilla, and provides a brief review of the literature because of the rarity and unusual radiographic-histologic features of this type of ameloblastoma.5*6 Report of a Case A 36-year-old Japanese woman was referred to the department of oral and maxillofacial surgery, Shimane Medical University Hospital, for examination and treatment of a tumor of the maxilla on October 13,198l. She gave a history of a left facial swelling beginning about 3 years previously that had become slightly enlarged since that time. There were no particular features of significance in the medical history except for appendicitis for which an appendectomy was performed when the patient was 22 years old. Examination showed a firm, painless swelling of the left maxilla (Fig 1). The growth had a bonelike hardness, was nontender, and had a normal mucous membrane cov-
ering. There were no enlarged regional lymph nodes or other abnormalities in the oral cavity or the nasopharynx. A panoramic radiograph showed an expansive, multilocular, ovoid tumor extending into the left maxillary sinus from the alveolar bone. The occlusal radiograph showed a multilocular, ill-defined lesion with a honeycomb appearance and an irregular border (Fig 2A). On computed tomographic (CT) imaging, the tumor was seen to have invaded the maxillary sinus. It had an indistinct boundary and possessed several small, high-density masses (Fig 2B). From these clinical and radiologic findings, possible diagnoses included ameloblastoma, odontogenic myxoma, calcifying epitheliat odontogenic tumor, fibrous dysplasia, reparative giant cell granuloma, and aneurysmal bone cyst. To obtain a correct diagnosis, a biopsy was taken, and the lesion was diagnosed as a desmoplastic ameloblastoma. The lesion was excised by a subtotal maxillectomy under general anesthesia on October 30, 1981. Macroscopically, the excised mass was composed of solid tissue in the inferior alveolar portion and cystic tissue in the upper portion of the maxilla. Histologic examination showed the tumor to be an atypical ameloblastoma, ie, generally composed of odontogenic epithelial islands and cords showing no clear ameloblastic polarization scattered in a pronounced desmoplastic stroma (Fig 3A). However, in some areas, the epithelial components showed peripheral cuboidal and/or columnar cell alignment, surrounding
stellate reticulum cells (Fig 3B). The central areas of the epithelial islands corresponding to stellate reticulum showed hypercellularity in some places (Fig 3C) and few cystic spaces in others (Fig 3D). The cells that composed the central hypercellular portion of these epithelial islands were spindle- or polygonal-shaped, whereas in the epithelial islands with cystic change, the cavity contained eosinophilic amorphous deposits or epithelial cell clusters, or was empty. An abundant collagenous fibrous connective tissue stroma seemed to compress the odontogenit epithelial islands from the periphery. Myxoid changes were also observed in one area (Fig 3D). A diagnosis of ameloblastoma, desmoplastic variant, was made. Because the patient was dissatisfied with the degree of facial deformity after the operation, reconstructive surgery was undertaken on April 28, 1989, which consisted of anterior maxillary augmentation with porous hydroxyapatite block (Fig 4). At present, April 10, 1990, the patient is well, without problems and lesion-free approximately 9 years later (Fig 5).
Discussion
FIGURE 4. A, Plaster model of patient’s life mask and wax model, used for facial reconstruction. B, The fabricated hydroxyapatite implant.
FIGURE 5.
In general, the occurrence of desmoplastic ameloblastoma is low. According to a histopathologic study of 116 ameloblastomas undertaken by Waldron and ElMofty,2 only 14 cases of the desmoplastic variant were identified. The study further showed that the maxilla is most frequently involved, and the lesions tend to develop in the anterior or premolar region.2 In mandibular desmoplastic ameloblastoma, lesions also are located in the premolar or anterior regions.’ They present as a tumor or swelling, in a similar fashion to other ameloblastomas.2*5*6 According to the review of the six cases in Table 1, the lesions all occurred in females, and four of the lesions were located from the anterior to the premolar region. In the two other cases, with large overgrown masses, the points of origin were not ascertainable.23536 These six cases, as well as the 14 cases of Waldron
Facial view (A) after the maxillary resection and (B) after reconstructive
surgery.
1234 Table 1.
Author(s)
DESMOPLASTIC
Cases of Desmoplastic Ameloblastoma Since First Reported by Eversole et al (1984)
Patient Age (yr)/Sex
Location
Chief Complaints or Symptoms
Eversole et al, 1984
SOIF
33
Swelling (nontender buccal expansion)
Eversole et al, 1984
47/F
from 33 to 43
Recent shifting of the anterior mandibular teeth
Right maxilla
Facial disfigurement caused by tumor Recurrent swelling
Eversole et al, 1984
VARIANT OF AMELOBLASTOMA
?/F*
Time Between Recognition of Symptoms and First Examination 2 mo
?
>16-18 yr
Gratz & Makek, 1988
59/F
Right premolar region
Gratz & Makek, 1988
33/F
Left maxilla
Maxillary swelling
6 yr
Yoshimura & Saito, 1990
36/F
Left maxilla
Maxillary bone expansion
3 yr
1 yr
* The patient was reported as a Malaysian woman approximately
and El-Mofty, were all intraosseous ameloblastomas.2,5,6 Generally, it is said that typical radiologic features of ameloblastoma are not observed in desmoplastic ameloblastoma. 2 The radiographic findings in six cases reported by Waldron and El-Mofty resembled fibro-osseous lesions in four cases, ameloblastoma simulating a radicular cyst in one case,
X-ray, CT Findings Scalloped radiolucency that exhibited alternating zones of lesional delineation and poor margination Diffuse, poorly delineated, mottled, radiolucencylradiopaque lesion
Massive expansile growth with a mottled appearance Osteolytic lesion with clear destructive invasion in the cortical portion of alveolar bone and small calcified material in the tumor Osteolytic lesion with expansive multilocular appearance, pushing up the left maxillary sinus (CT picture) Massive expansile growth with honeycomb appearance and ill-defined margin, and uneven density tumor with indistinct margin (CT picture)
Treatment
Remarks
?
Block resection and reconstruction employing metallic crib with cancellous bone and hematopoietic marrow Hemimaxillectomy and maxillary prosthesis
An initial trephine bone biopsy indicated an atypical epithelial odontogenic neoplasm or hamartoma
Mandibular resection and iliac bone transplantation
The lesion was operated on as a cyst 1 yr before Free from tumor for 13 yr
Maxillary resection and reconstruction with lyophilized cartilage
The patient first visited the clinic for other complaints Free from tumor for 9 mo
Partial maxillectomy and reconstruction with apatite
Free from tumor for about 9 yr
Free from tumor for 2 yr
45 to 50 years of age.
and a large globulomaxillary cyst in the other. Furthermore, the following radiographic features were noticed: localized irregular radiolucency with an indistinct border, ill-defined margins mixed with a radiolucentkadiopaque appearance, and tine, irregular calcifications in the peripheral portion of the lesion.2,5*6 Radiologically, the case reported in this article not
YOSHIMURA
1235
AND SAITO
only showed multilocular spaces, but also radiolucency-radiopacity in an ill-defined expansive pattern. Another imaging feature was the unclear boundary between the tumor and normal tissue. At first, we suspected a calcifying epithelial odontogenit tumor or a fibro-osseous lesion, rather than an ameloblastoma. Computed tomography scans in this case showed that the tumor seemed to invade the alveolar process and palatal bone, with an obscure boundary between the tumor and normal tissue. The internal structure had a slightly higher density than the surrounding soft tissue and contained several highdensity masses. These high-density masses were probably residual bone particles. Typically, small lesions of this variant may be well circumscribed and easily enucleated in toto from the intraosseous bed,2 but larger tumors generally possess no clear separation from normal tissue, suggesting a locally aggressive behavior. The cut surface in our case showed a solid appearance; however, the portion protruding into the maxillary sinus also contained cystic areas. As already described, marked stromal desmoplastic tissue proliferation is one of the most important features of this lesion. Such extensive stromal desmoplasia in epithelial tumors might inhibit growth of tumor cells. This finding was indirectly supported by Shivas and Douglas,’ who reported long survival rates in patients with elastosis in breast carcinoma. Myxoid areas have been observed in several cases,2 which also was true in this case. Other tumors that must be histologically differentiated from this type of ameloblastoma include basal cell-type ameloblastoma, ameloblastic fibroma, odontogenic fibroma, and, in particular, squamous odontogenic tumor.8 However, an abundant desmoplastic proliferation of the stroma, loss of mature, cell-rich connective tissue, and existence of some ameloblastoma-like structures should lead to the correct diagnosis. The biologic behavior of this variant is said to be similar to other types of ameloblastoma,’ except for unicystic ameloblastoma, which has clinical, radiographic, and gross features more closely resembling
a non-neoplastic cyst and with a less aggressive biologic nature.’ No reports of a malignant form of desmoplastic ameloblastoma have been found in the literature. Although various treatments have been proposed,4 complete resection is recommended for the desmoplastic ameloblastoma to avoid recurrence, because of the lack of distinct boundaries between the tumor and normal tissues in many cases.5*6 It has been shown that enucleation or curettage of this variant results in recurrence.” The prognosis of this type of ameloblastoma has not been clearly established because of the lack of documentation, although the cases in Table 1 were satisfactorily resolved with surgery. Summary A case of desmoplastic variant of ameloblastoma is reported. The lesion, in a 36-year-old Japanese woman, was successfully treated by partial maxillectomy. Reconstruction was carried out with a block of hydroxyapatite about 7 years and 6 months later. Six cases, including our case, reported up to the present are summarized and reviewed. References 1. Regezi JA, Kerr DA, Courtney RM: Odontogenic tumors: Analysis of 706 cases. J Oral Surg 36:771, 1978 2. Waldron CA, El-Mofty SK: A histopathologic study of 116 ameloblastomas with special reference to the desmoplastic variant. Oral Surg 63:441, 1987 3. Pindborg JJ, Kramer IRH: Histological typing of odontogenie tumours, jaw cysts, and allied lesions. Geneva, World Health Organization, 1971 4. Gardner DC, Pecak AMJ: The treatment of ameloblastoma based on pathologic and anatomic principles. Cancer 46:2514, 1980 5. Eversole LR, Leider AS, Hansen LS: Ameloblastomas with pronounced desmoplasia. J Oral Maxillofac Surg 42:735, 1984 6. G&z KW, Makek M: Das desmoplastische Ameloblastom Ein neuer motphologischer Subtyp des Ameloblastoms. Dtsch Z Mund Kiefer Gesichts Chir 12:445, 1988 7. Shivas AA, Douglas JG: The prognostic significance of elastosis in breast carcinoma. J Roy Co11 Surg Edinb 17:315, 1972 8. Pullon PA, Shafer WC, Elzay RP, et al: Squamous odontogenie tumor. Report of six cases of a previously undescribed lesion. Oral Surg 40:616, 1975 9. Robinson L, Martinez MC: Unicystic ameloblastoma. A prognostically distinct entity. Cancer 40:2278, 1977