Cranial fasciitis.

We present the clinical, roentgenographic, light-microscopic, immunohistochemical, and ultrastructural findings in two children with cranial fasciitis. A 7-year-old boy and a 3-year-old girl presented with rapidly expanding masses on the scalp. Roentgenographic studies showed erosion of the underlying cranium in one case. Both lesions showed proliferations of elongated spindle cells in a focally myxoid matrix, together with areas of hemorrhage, vascular proliferation, and chronic inflammation. Occasional cells with atypical nuclei were observed, but mitotic figures were uncommon. Immunoperoxidase studies showed negative or equivocal staining for desmin, factor VIII-associated antigen, S100 protein, and macrophage antigen. In one lesion there was focal positivity for alpha 1-antichymotrypsin, and in another lesion, some cells stained positively for smooth-muscle actin. Electron microscopy showed cells with dilated endoplasmic reticulum, bundles of microfilaments, pinocytotic vesicles, and focal external membrane material, features of myofibroblasts. Both lesions were excised and there has been no recurrence in 7 years in one case and 1 year in the other case. Cranial fasciitis is closely related to nodular fasciitis, but it has a predilection for the scalp of children. Despite its rapid growth, it has a benign clinical course and is cured by excision with or without curettage of the underlying bone. Our immunohistochemical and ultrastructural observations indicate that, like nodular fasciitis, cranial fasciitis represents a proliferation of fibroblasts and myofibroblasts.