Primary cutaneous mucoepidermoid carcinoma: a case study with a review of the literature

Mucoepidermoid carcinoma (MEC) of the skin is a rare neoplasm with few cases reported in the medical literature. We report a case of MEC of the skin in a 76-year-old man who presented with an infiltrative multinodular lesion on his right cheek. Histological description showed a multilobulated nodulocystic tumor extending throughout the dermis exhibiting glandular and squamoid differentiation. Cribiform nests of epidermoid cells contained glandular spaces with mucin. The nuclei were mildly atypical and contained scattered mitotic figures. A small focus of perineural invasion was evident within the tumor not extending beyond the deep margin with no lymphovascular invasion. There was no overlying intraepidermal carcinoma. Immunohistochemical analysis revealed staining for EMA, PanCK, and p63 whereas CK7, CK20, and CEA were negative. It is important to differentiate primary cutaneous MEC from cutaneous adenosquamous carcinoma, direct extension from an underlying primary salivary gland MEC, or metastasis of MEC from another site. We conclude that primary MEC of the skin is a low-grade neoplasm that should be differentiated from adenosquamous carcinoma. Immunohistochemical staining for p63 has proven to be helpful in differentiating primary epidermal or adnexal tumours and metastatic neoplasms to the skin.