Myoepithelial carcinoma of the posterior mediastinum: An uncommon site for a rare tumor

Myoepithelial carcinoma (MC) is a rare tumor that arises from myoepithelial cells; most commonly in the salivary glands, but other infrequent body sites such as the breast, lung, lower limb, upper limb, head and neck, vulva, and vagina can be involved. We report the first case of myoepithelial carcinoma arising in the posterior mediastinum of a 51 year-old male who presented with a mediastinal mass and subsequently underwent tumor debulking surgery. Grossly, the specimen consisted of multiple tan–gray firm fragments of tissue with an overall measurement of 7.0 cm in greatest dimension. Histologic examination revealed an ill-defined, infiltrative lesion with a biphasic cell population. The tumor cells were diffusely positive for epithelial and myoepithelial markers, confirming the above diagnosis. Recognition of this entity at an uncommon site may present a diagnostic challenge due to its morphologic heterogeneity and the differential diagnosis includes benign and malignant tumors, which could lead to over or under-treatment, respectively