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Melanotic Progonoma: An Unusual Pathology for an Infantile Midline Scalp Mass

blast cells with dense nuclei and scant cytoplasm and some large melanin-pigmented epithelial cells with large vesicular nuclei and prominent nucleoli ( fig. 2 a, b). Immunohistochemistry was positive for synaptophysin (SY38), cytokeratin (AE1/AE3), HMB45, chromogranin (DAKA3), neuron-specific enolase (BBS/NC/Vi-H14) and negative for leukocyte common antigen, S100, desmin and MIC2 (CD99), all consistent with the diagnosis of melanotic neuroectodermal tumor of infancy. Melanotic neuroectodermal tumor of infancy is a rare neoplasm of neural crest origin which usually affects infants during the first year of life [1] . It is also called melanotic progonoma [2] . It occurs most commonly in the maxilla, but mandible, skull, and brain may also be rarely involved [1, 2] . Despite its rapid local growth, melanotic neuroectodermal tumor of infancy is considered as a benign neoplasm. In MRI, the paramagnetic effect of melanin causes the tumor to show increased signal on T1A 10-month-old female infant was referred to our center due to a bulging mass in the scalp midline. This bulging was first noticed about 3 months earlier and had gradually grown to its present size. On clinical examination, there was a firm, nontender mass measuring 3.4 cm in the midline of the head posterior to the coronal suture with no overlying skin changes. There was no evidence of any neurological deficit. A plain radiograph of the skull showed bone expansion and calvarial hyperostosis. Magnetic resonance imaging (MRI) revealed a well-defined subcutaneous lesion of oval shape measuring 4 × 3 × 2.5 cm in the midline of the high skull without involvement of the dura mater or brain parenchyma. The lesion showed hypersignal on T1-weighted and isoto hyposignal on T2-weighted images ( fig. 1 a, b). The patient underwent en bloc total resection of the lesion. The surgery was relatively straightforward; there were no dural adhesions, and bleeding was insignificant. Histopathology showed a biphasic pigmented neoplasm, composed of clusters of tumor cells in nests and cord-like patterns set in a dense collagenous stroma. Tumor cells had a biphasic proliferation pattern: some small neuroReceived: September 11, 2013 Accepted after revision: April 8, 2014 Published online: July 15, 2014