title: An unusual round cell tumor of the tibia with granular cells.
abstract: We present the clinical, radiographic and histopathologic findings of an unusual tumor that originated in the diaphysis of the tibia in a 10-year-old boy. Clinical symptoms had been present for approximately 2 years and radiographic abnormalities for > or = 8 months before biopsy and subsequent resection of the neoplasm. The child is doing well 4 1/2 years later. Microscopically, the tumor was not typical of any bone tumor with which we are familiar. It was a round-cell tumor with extensive fibrosis, prominent cytoplasmic granularity, and isolated immunoreactivity for vimentin, epithelial membrane antigen, and antichymotrypsin. Ultrastructural examination uncovered the presence of both well-formed desmosomes and cell-associated basement membrane material in addition to abundant phagolysosomes. Classification of this tumor is a challenge; the differential diagnosis includes atypical adamantinoma, atypical Ewing's sarcoma, and small-cell osteosarcoma. We favor the former interpretation, although we raise the possibility that it may be a unique lesion.
authors.affiliation: Department of Pathology, Children's Hospital and Medical Center, Seattle, Washington, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Schofield
authors.forename: E U
authors.initials: EU
authors.lastname: Conrad
authors.forename: R M
authors.initials: RM
authors.lastname: Liddell
authors.forename: E J
authors.initials: EJ
authors.lastname: Yunis
mesh_terms: D001859:Bone Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D002648:Child; D003937:Diagnosis, Differential; D016586:Granular Cell Tumor / Q000473:pathology* / Q000648:ultrastructure; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008854:Microscopy, Electron; D013977:Tibia / Q000648:ultrastructure