Epithelioid leiomyoma of the oral mucosa

Epithelioid leiomyoma of the oral mucosa Ioannis G. Koutlas, DDS, MS, a and J. Carlos Manivel, M D , b M i n n e a p o l i s , M i n n . SCHOOL OF DENTISTRY AND MEDICAL SCHOOL, UNIVERSITY OF MINNESOTA

Oral leiomyomas are rare because of the paucity of smooth muscle in the mouth. The solid and vascular types are the most frequent variants. The purpose of this article is to present the pathologic features and differential diagnosis of an example of epithelioid leiomyoma. A 50-year-old woman presented with a small raised nonpainful polypoid lesion of unknown duration on the right buccal mucosa. The tumor was well demarcated and consisted of large epithelioid cells with distinct cytoplasmic borders, round to oval nuclei, and prominent nucleoli. A few mitoses (4 in 20 high power fields) were present. :Scattered spindle cells were also seen. The cytoplasm was eosinophilic to amphophilic and showed frequent clearing and retraction. Small capillaries were identified and surrounded by neoplastic cells that gave the lesion an angiomyomatous appearance. Masson trichrome stain highlighted focally smooth muscle cells. lmmunohistochemical evaluation revealed staining for vimentin, desmin, and muscle-specific actim. (Oral Surg Oral Med

Oral Pathol Oral Radiol Endod 1996;82:670-3)

L e i o m y o m a s are b e n i g n smooth muscle tumors that occur most often i n the uterus and the gastrointestinal tract. A c c o r d i n g to the W o r l d Health Organization, l e i o m y o m a s are divided into three histologic variants i n c l u d i n g solid, vascular (angiomyoma), and epithelioid; the last is the least c o m m o n . Oral leio m y o m a s are considered u n c o m m o n neoplasms because of the paucity of smooth muscle in the mouth. W h e n encountered, they most often occur in the tongue, the palate, buccal mucosa, and lip. The solid and vascular types are the most frequent. O n l y one report 1 featured histologic and cytologic patterns consistent with the epithelioid variant; that tumor was located in the lip and was diagnosed as atypical leio m y o m a . Epithelioid l e i o m y o m a , also referred to as l e i o m y o b l a s t o m a or " b i z z a r e " l e i o m y o m a , has b e e n observed almost exclusively in the a b d o m i n a l cavity, gastrointestinal tract, and uterus. 2 A few cases have b e e n reported in the upper and lower respiratory tract 3 and one in the skin. 4 CASE REPORT A 50-yearcold woman presented with a small, raised, nonpainful, polypoid lesion on the right buccal mucosa. The overlying mucosa was of normal color. The duration

aAssistantProfessor, Department of Oral Science, Division of Oral Pathology, School of Dentistry, University of Minnesota, Minneapolis. bprofessor, Department of Laboratory Medicine and Pathology, Division of Surgical Pathology, Medical School, University of Minnesota, Minneapolis. Received for publication Mar. 15, 1996;returned for revision Apr. 18, 1996; accepted for publication July 2, 1996. Copyright 9 1996 by Mosby-Year Book, Inc. 1079-2104/96/$5.00 + 0 7114176382

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was not stated. The lesion was excised and no recurrence was reported subsequently.

Pathologic findings The polypoid lesion measured 0.5 cm in greatest diameter. The cut surface was firm and white. Histologically, it was covered by normal keratinizing stratified squamous epithelium (Fig. 1). The tumor was characterized by a proliferation of large epithelioid cells with distinct cytoplasmic borders. Individual nuclei were round to oval and demonstrated a fine chromatin pattern (Fig. 2). Spindle-shaped and blunt-ended nuclei characteristic of leiomyomas were uncommon. The cytoplasm was eosinophilic to amphophilic, and frequent clearing was observed. In many cells the cytoplasm was retracted toward the nucleus. Occasionally, nuclei appeared vesicular and revealed prominent nucleoli. A few regular mitoses (4 per 20 high power fields [HPFs]) were present. Scattered spindle cells were also identified. Small capillaries were also identified within the stroma and surrounded by the neoplastic cells giving the lesion an angiomyomatous appearance. Although a capsule was not identified, delineation of the lesion and separation from adjacent connective tissues was obvious. The surgical margins were free of tumor. Masson trichrome stain depicted, infrequently, smooth muscle cells with characteristic elongated cytoplasmic processes. I m m u n o h i s t o c h e m i c a l stains were performed for vimentin, muscle-specific actin (MSA), desmin, S-100, neuron-specific-enolase (NSE), KP-1 (CD68, monocyte/ macrophage marker), a-antitrypsin (AAT) and a-antichymotrypsin (AACT) using the avidim-biotim-complex (ABC)method. Positive immunostaining was obtained for vimentin, MSA, and desmin (Fig. 3).

DISCUSSION Epithelioid l e i o m y o m a s are exceedingly rare in locations other than the a b d o m i n a l cavity, gastrointestinal tract, and uterus. In the literature, there are no

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Fig. 1. Panoramic view depicts polypoid well-demarcated lesion covered by stratified squamous epithelium. (Hematoxylin-eosin stain; original magnification x7.5.)

Fig. 2. Epithelioid cells with large vesicular nuclei. Note retraction of cytoplasm and clear appearance of individual cells. (Hematoxylin-eosin stain; original magnification x200.)

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ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY December 1996

Fig. 3. Neoplastic ceUs stain for desmin. (ABC method, hematoxylin counterstain; original magnification xlO0.)

documented lesions arising in the oral cavity. There is only one example arising on the lip. 1 The characteristic cytologic criteria of conventional leiomyomas are not present in the epithelioid variants; likewise, M a s s o n trichrome stain, which characteristically highlights the cytoplasm of conventional smooth muscle tumors, is not very helpful in the epithelioid variants. The smooth muscle phenotype should be confirmed with immunohistochemical or ultrastructural methods. Several neoplasms that exhibit epithelioid morphologic characteristics should be considered in the differential diagnosis. Nerve sheath neoplasms including schwannoma, neurofibroma, and the epithelioid variant of solitary circumscribed (palisaded and encapsulated) neuroma 5 were excluded because o f negative S-100 and neuron-specific enolase staining. In addition, the lesion was not encapsulated. The diagnosis of epithelioid h e m a n g i o m a was not considered likely because there were no epithelioid cells lining capillaries. Epithelioid histiocytoma 6 was not considered a choice because o f negative immunostaining of neoplastic cells for A A T , A A C T and with KP-1 antibody. In epithelioid histiocytoma cytoplasmic clearing is not a distinct feature. Diagnostic criteria o f malignant conditions, as seen in epithelioid

leiomyosarcoma, 2 were absent. Although a few mitoses were identified, the lesion was small (0.5 cm), superficial, polypoid, and well-circumscribed. Myofibroblastoma or myofibroblastic reactive proliferations were also included in the differential diagnosis. There is only one reference o f myofibroblastoma of the oral m u c o s a arising in the tongue. 7 That lesion exhibited immunoreactivity for smooth muscle actin but not for desmin. However, myofibroblastomas have been reported to express desmin 8 and not actin 9 or to express b o t h J ~ The diagnosis of a m y o fibroblastoma was not favored in the present case because of the distinct histologic features of individual neoplastic cells.

REFERENCES

1. Hagy DM, Halperin V, Wood III C. Leiornyoma of the oral cavity: review of the literature and report of a case. Oral Surg Oral Med Oral Pathol 1964;17:748-55. 2. Enzinger FM, Weiss SW, editors. Epithelioid smooth muscle tumors. In: Soft tissue tumors. 3rd ed. St. Louis: Mosby, 1995:511-22. 3. Hellquist HB, Hellqvist H, Vejlens L, Lindholm CE. Epithelioid leiomyoma of the larynx. Histopathology 1994;24:155-9. 4. Musso LA, Rae JM. Epithelioid leiomyorna: a case report. Aust J Dermatol 1982;23:116-8. 5. Tsang WY, Chan JK. Epithelioid variant of solitary circumscribed neuroma of the skin. Histopathology 1992;20:439-41.

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Volume 82, Number 6 6. Glusac EJ, 13arr RJ, Everett MA, Pitha J, Santa Cruz DJ. Epithelioid cell histiocytoma: a report of 10 cases including a new cellular variant. Am J Surg Pathol 1994;18:583-90. 7. Sabin AA, Ro JY, Ordofiez NG, Luna MA, EI-Naggar AK, Goepfert H, et al. Myofibroblastoma of the tongue: an immunohistochemical, ultrastructnral, and flow cytometric study. Am J Clin Pathol 1990;94:773-7. 8. Wargotz ES, Weiss SW, Norris HJ. Myofibroblastoma of the breast: sixteen cases of a distinctive benign mesenchymal tumor. Am J Surg Pathol 1987;11:493-502. 9. Fletcher CD, Tsang WY, Fischer C, Lee KC, Chan JKC. Angiomyofibroblastoma of the vulva: a benign neoplasm

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distinct from angiomyxoma. Am J Surg Pathol 1992;16:37382. 10. Hen'era GA, Johnson WW, Lockard VG, Walker BL. Soft tissue myofibroblastomas. Mod Pathol 1991;4:571-7.

Reprint requests: Ioannis G. Koutlas, DDS, MS Assistant Professor Division of Oral Pathology University of Minnesota 515 Delaware Street S.E. #16-127 Minneapolis, MN 55455

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