INTRACISTERNAL COLLAGEN FIBRILS IN PROLIFERATIVE FASCIITIS AND MYOSITIS OF CHILDHOOD

During ultrastructural examination of a difficult to diagnose tumor, s hort spacing collagen fibrils (periodicity of banding, approximately 4 3.2 nm) and native collagen fibrils (periodicity of banding, approxima tely 53 nm) were found in dilated and vacuolated cisternae of rough en doplasmic reticulum and the perinuclear cistern. Original diagnoses fr om several histopathologists included alveolar soft part sarcoma, mali gnant fibrous histiocytoma, atypical fibroxanthoma, and myogenic tumor . The finding of intracisternal collagen (which is but a variety of in tracellular collagen) led to the conclusion that this was a fibroblast ic neoplasm. This, plus a review of the histologic findings, led to th e diagnosis of proliferative fasciitis and myositis of childhood.