Mucoepidermoid carcinoma of the breast: high grade variant.

The mucoepidermoid carcinoma is a very rare neoplasm of the breast which histologically resembles mucoepidermoid carcinoma in the salivary glands. It is characterized by sheets of epidermoid cells with area of definite squamous differentiation as well as glandular and cystic spaces lined by atypical mucin-secreting columnar cells. The ultrastructural findings reflect the squamous and adenomatous differentiation seen on light microscopy. The degree of histological differentiation and the infrequency of nodal metastasis suggest an indolent behaviour. This is supported by the absence of recurrence or death due to the disease in 7 of the 8 cases reported to date. Only 1 patient has had extensive axillary nodal metastasis from a mucoepidermoid carcinoma which showed large areas of poorly differentiated cells. The present case is another example of such a high grade variant in which death occurred from pulmonary and vertebral metastases within 6 mth of mastectomy. An aggressive behaviour should be predicted by the presence of a large undifferentiated component in the tumour, necrosis and prominence of mitoses.