title: Parachordoma exists--but what is it?
abstract: Parachordoma is a very rare peripheral soft tissue tumor of unknown lineage, which has been described under other names, all of which imply a similarity to chordoma. It forms a circumscribed firm tumor, usually in deep soft tissue, with a variety of histologic patterns and cytologic features, including cords and nests of cells, some of which are vacuolated. The ultrastructure and immunophenotype indicate epithelial differentiation and parachordomas are additionally S-100 protein positive. This tumor is distinct from extraskeletal myxoid chondrosarcoma and probably from soft tissue myoepithelioma. While histologically it somewhat resembles chordoma, parachordoma has a wider range of appearances, and the two neoplasms differ in their detailed cytokeratin immunophenotype and their clinical behavior. Parachordoma is a slowly growing tumor with occasional late recurrence; cases with reported metastasis have not been histologically convincing. This commentary discusses the terminology, origin, and possible nature of this enigmatic neoplasm.
authors.affiliation: Royal Marsden Hospital, London, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Fisher
mesh_terms: D000293:Adolescent; D000328:Adult; D001132:Arm; D002081:Buttocks; D002648:Child; D002812:Chondroma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D003094:Collagen / Q000032:analysis; D005205:Fascia; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009006:Monosomy; D009418:S100 Proteins / Q000032:analysis; D012983:Soft Tissue Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D013848:Thigh; D013909:Thorax; D014314:Trisomy
chemical_list: D009418:S100 Proteins; D007633:Keratins; D003094:Collagen