A rare malignant tumor of scalp in a 3-month-old Taiwanese infancy: case report of primitive myxoid mesenchymal tumor of infancy with molecular study.

Primitive myxoid mesenchymal tumor of infancy is an extremely rare and recently recognized soft tissue tumor entity with a tendency for multiple recurrences. Only ten cases have been described in the literature and most cases are reported in Western countries. This tumor ranges in size from 2 to 15 cm and is characterized microscopically by a diffuse growth of primitive cells in a myxoid background with focal fascicles or a herringbone pattern. In this study, we describe a primitive myxoid mesenchymal tumor of infancy on the scalp of a 3-month-old Taiwanese boy. The histology showed typical morphology and the tumor cells showed vimentin and CD99 immunoreactivities. The translocation t(12,15)(p13;q25) was not found by fluorescence in situ hybridization. After complete surgical excision, no recurrence was noted during an 18-month follow-up.