Primary mediastinal melanotic schwannian tumors: A clinicopathological and immunohistochemical study of 5 cases

Mediastinal neurogenic tumors are unusual and more so is the presence of melanotic neurogenic tumors. We present five cases of mediastinal melanotic neurogenic tumors. The patients are five men between the ages of 34 and 43 years (average: 38.5 years). All patients presented with non-specific symptoms that included back pain and cough. Diagnostic imaging revealed the presence of a posterior mediastinal mass without connection to the spinal canal, and surgical resection was accomplished in all of the patients. Histologically, the five tumors showed a spindle epithelioid cellular proliferation, nuclear atypia, mitotic activity, and melanin deposition. Histochemical stain for Fontana Masson clearly demonstrated the presence of melanin pigment in all the cases, while S-100 protein was only focally positive in tumor cells. Other immunohistochemical stains including SOX-10, MITF, HMB-45, and Melan A were negative. Clinical follow-up showed that two patients died 22 and 30 months after initial diagnosis; one remains alive, 6 months after initial diagnosis; two patients were lost to follow up. Melanotic neurogenic tumors represent a diagnostic challenge for pigmented thoracic tumors and careful analysis of the morphology and immunohistochemistry is required to lead to proper diagnosis.