December 2004: one-year-old girl with aggressive skull tumor.

December 2004. Twelve-month old girl presented with recurrent subcutaneous lesion in the left parietal region, one year after excision of a "benign" tumor. An MRI demonstrated left temporo-parietal skull tumor infiltrating the soft tissue, surrounding craniotomy flap, and extending to the brain parenchyma. Biopsy revealed biphasic neoplasm displaying nests of poorly differentiated neuroblastic cells positive for synaptophysin and pigmented cuboidal epithelioid cell positive for keratins, epithelial membrane antigen and MHB-45. In addition, some neoplastic cells were immunoreactive for synaptophysin as well as HMB-45 and epithelial markers, suggestive of their origin from a common progenitor. Interestingly, cell with the neuroblastic immunophenotype displayed 80% nuclear MIB-1 reactivity indicating that the aggressiveness of the neoplasm was confined mostly to this pattern of differentiation. The overall histological features are consistent with a rare malignant variant of a melanotic neuroectodermal tumor of infancy.