Myoepithelial Carcinoma of Soft Tissue: A Case Report and Review of the Literature

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Myoepithelial carcinoma of soft tissue is extremely rare although its counterpart of the salivary gland is relatively common and well-known with similar morphology. The histogene-sis of myoepithelial carcinoma of soft tissue is still unknown. In fact, the tumor may present with myoepithelial differentiation but not originate from myoepithelial cells. 1 The tumor cells are heterogeneous in terms of cell type and architecture. The tumor cells may be epithelioid, spindled, clear, or plasmacytoid. The growth pattern varies and can be solid sheets, reticular, or tra-becular architecture without ductal differentiation. 2 Myoepithe-lial carcinoma usually shows cytologic atypia, mitotic activity, infiltrative growth, or tumor necrosis. 2 Only few studies have been reported because of the rarity of myoepithelial carcinoma of soft tissue. Consequently the clinical and pathologic characterization has been limited. Also, the limitation of definite diagnostic criteria and prognostic parameters makes the diagnosis and management of myoepithelial carcinoma of soft tissue difficult. Here we report the first case of myoepithelial carcino-ma of soft tissue in Korea. A 69-year-old male presented with a palpable mass in the right shoulder area. The mass had been noted 6 months prior and the size of the mass had recently increased. On physical examination , the round and firm mass was fixed on the upper aspect of the right scapula without tenderness. The sonography revealed a heterogeneous echoic solid mass. A local excision was performed. The mass was located in the subcutaneous soft tissue just above the trapezius muscle and measured 4.0×3.5×2.0 cm. The solid mass was lobulated and the cut surface of the mass was gray tan with multiple necrotic foci (Fig. 1A). The tumor was confined to the subcutaneous soft tissue without dermal invasion. Although the tumor showed a well-circumscribed lobu-lating border, microscopic tumor infiltration into the adjacent soft tissue was observed (Fig. 1B). The tumor presented with various histologic growth patterns including solid sheet, tra-becular, reticular patterns, and short fascicle with myxoid and hyalinized stroma. Although tumor cells had a heterogeneous cytomorphology consisting of epithelioid cells, spindle cells, clear cells, and plasmacytoid cells, the tumor cells generally showed vesicular or coarse chromatin, distinct nucleoli, and thick irregular nuclear membrane (Fig. 2). Numerous mitoses were noted (up to …