Primary Myoepithelioma of Bone

Abstract

The clinical and pathologic features of 8 primary myoepitheliomas of bone were analyzed. There were 5 female and 3 male patients who ranged in age from 16 to 49 (mean, 33.5) years. Three tumors arose in the ilium, 2 in the tibia, and 1 each in the maxilla, sacrum, and L1 vertebral body. Microscopically, the tumors had a solid, lobulated, reticular, or storiform growth pattern and were predominantly composed of spindle-shaped cells arranged in intersecting fascicles with eosinophilic cytoplasm. The round to polygonal epithelioid cells were arranged randomly or formed small clusters and contained variable amounts of eosinophilic or clear cytoplasm. Immunohistochemically, all the tumors were positive for vimentin and S100 protein, and 7 were positive for epithelial membrane antigen. No tumors were positive for keratin (AE1.3/CAM5.2). Smooth muscle actin was positive in 3 tumors and negative in 4, whereas desmin was negative in all 7 tumors tested. Nuclear staining for p63 was negative in 3 tested tumors. Staining for GFAP and CD34 was performed on 4 and 5 tumors, respectively, and all showed no expression. Fluorescence in situ hybridization for EWSR1 rearrangement was performed in 7 tumors. Five tumors (71%) showed the presence of EWSR1 gene rearrangement, and 2 were negative. Cytogenetic studies conducted on 1 tumor showed 46,XY,t(1;22)(q21;q12) associated with EWSR1-PBX1 fusion. Surgical procedures included curettage in 3 patients, resection in 3 patients, and 2 patients only had an open biopsy. Follow-up information was available for 4 patients; all remain free of disease with no recurrence. Although experience with primary myoepithelioma of bone is limited, histologically, banal tumors appear to behave in a benign manner, and conservative surgery appears to be sufficient treatment. Immunohistochemical and molecular analyses are helpful in their accurate identification.

Angiomatoid Fibrous Histiocytoma: The Current Status of Pathology and Genetics

“…Myoepithelial tumors also variably express glial fibrillary acidic protein, smooth muscle actin, calponin, and CD10. EWSR1 rearrangements have been described in about half of soft tissue myoepithelial neoplasms, resulting in fusions with a small group of partner genes, including the POU5F1 gene, [81][82][83] PBX1 gene, 81,84,85 and ZNF444 gene. 81,86 The association of myoepithelial tumors with EWSR1-CREB1, EWSR1-ATF1, or FUS-ATF1 fusions has not been documented, except in one case of a pelvic myoepithelioma, which was described as having the EWSR1-ATF1 fusion.…”

Myoepithelial Tumors

“…5,46 MICROSCOPIC FEATURES Myoepithelial neoplasms in bone show similar morphologic features with soft tissue and skin tumors; most reported tumors are benign. Myoepitheliomas in bone are well-circumscribed multinodular and lobulated tumors with tumor cells arranged in solid and reticular growth patterns within a collagenous, myxoid, and hyalinized stroma (Fig.…”

“…As expected, tumors are positive for EMA and S-100 protein, and show variable reactivity for p63, GFAP, and keratin (AE1/AE3, Cam5.2). 5 …”

“…[1][2][3] Tumors most commonly arise in the subcutis of the extremities and proximal limb girdles; however, they may occur over a broad anatomic distribution (including deep-seated, visceral, and bone locations). [4][5][6] Cutaneous lesions are confined to the dermis and arise frequently in the extremities, trunk, and head and neck regions. [7][8][9] Tumors are classified as mixed tumor/chondroid syringoma, myoepithelioma, and myoepithelial carcinoma.…”

“…Myoepithelial neoplasms show coexpression of epithelial markers (cytokeratin and/or epithelial membrane antigen [EMA]) and S-100 protein. [1][2][3]7,8,10 EWSR1 gene rearrangement has been identified in nearly half of all myoepitheliomas and myoepithelial carcinomas in soft tissue, skin, and bone, as well as rare alternate FUS gene rearrangement [4][5][6][11][12][13][14] ; likewise, EWSR1 gene rearrangement is present in a subset of primary salivary myoepithelial neoplasms (many of which are characterized by clear-cell morphology). 15 At least two-thirds of mixed tumors harbor pleomorphic adenoma gene 1 (PLAG1) gene rearrangement, [16][17][18] similarly PLAG1 gene alterations are present in up to 88% of pleomorphic adenoma 19 and 63% to 75% of carcinoma ex pleomorphic adenoma.…”