Mucoepidermoid carcinoma with extensive spindled morphology and melanocytic marker expression

Publication date: Available online 12 April 2017
Source:Human Pathology
Author(s): Takashi Oide, Kenzo Hiroshima, Yoko Takahashi, Kazunori Fugo, Masanobu Yamatoji, Atsushi Kasamatsu, Yosuke Endo-Sakamoto, Masashi Shiiba, Katsuhiro Uzawa, Hideki Tanzawa, Toshitaka Nagao, Yukio Nakatani
Mucoepidermoid carcinoma (MEC) is the most common malignant neoplasm of the salivary gland. Albeit common, histological variants have rarely been noted in MEC. Here, we report a 49-year-old man with a sublingual gland tumor. Histologically, the tumor was composed of spindle cells arranged in interlacing fascicules or globular nests. A few bland small glands containing mucous cells were also scattered. The spindle tumor cells completely lacked immunoreactivity for cytokeratin, and exhibited immunoreactivity for vimentin, S-100, HMB-45, Melan A, and SOX10. The tumor was initially suspected to be clear cell sarcoma, malignant melanoma, or PEComa with a few entrapped non-neoplastic duct epitheliums. However, RT-PCR revealed the CRTC3-MAML2 fusion gene product diagnostic of MEC. In fact, a very minor component of the epithelial cells was reminiscent of conventional MEC, whereas major spindled tumor cells possessed markedly altered differentiation. This is the first case report of MEC with extensive spindled morphology and melanocytic marker expression.



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