Aggressive CD34-positive fibrous scalp lesion of childhood: extrapulmonary solitary fibrous tumor.

Although solitary fibrous tumor (SFT) was originally described as a pleural tumor, an increasing number of extrapleural sites of SFTs have been documented. This has been attributed not only to the heightened awareness of the spectrum of histopathological features that characterizes SFTs but also to the recognition of the role of CD34 immunostaining in soft tissue tumors in general, and in SFTs in particular. Despite the large number of documented extrapleural SFTs in adults, cranial SFTs are rare, having been documented in the meninges, scalp, and infratemporal fossa. Extrapleural SFTs are, to date, an unrecognized entity in children. We document an aggressive fibrous scalp lesion in a 30-month-old female child that demonstrated features common to benign cranial fasciitis and SFT. However, based on bright, diffuse CD34 antigen immunopositivity, a diagnosis of SFT was made. The need to include the CD34 antigen stain in a panel of immunohistochemical markers used to assess spindle cell lesions of childhood is emphasized.