"What the Mind Does Not Know, the Eye Does Not See": Epididymal Melanotic Neuroectodermal Tumor of Infancy Misdiagnosed as Paratesticular Rhabdomyosarcoma-A Rare Case Report.

Extra-testicular scrotal masses may be seen in young children, spanning a broad spectrum of lesions from benign entities to aggressive malignancies. Though rare, melanotic neuroectodermal tumor of infancy (MNTI) is a very important differential diagnosis of scrotal masses in infants due to its close histologic resemblance to more aggressive malignant small round cell tumors involving this region. An 18-month-old baby presented with a 10-month history of a scrotal mass, which was surgically excised and initially misdiagnosed as rhabdomyosarcoma, with a plan for post operative chemotherapy. Histopathologic review at our institute, with immunohistochemical support led to the correct diagnosis of MNTI, thus avoiding unnecessary chemotherapy. Morphologic findings and detailed differential diagnosis of this rare tumor are discussed.