title: Digestive PEComas: a solution when the diagnosis fails to "fit".
abstract: We report two cases of digestive/intra-abdominal PEComa. The first lesion developed in the caecum of a 36-year-old woman, the second in the pararectal region of a 35-year-old woman. The first tumor was formed from spindle cells arranged in fascicles, the second contained predominantly epithelioid cells with prominent nucleoli. Immunohistochemically, tumor cells expressed smooth muscle actin and melanocyte markers (HMB45), S-100 protein and CD117 were negative. Based on the morphologic aspect and, above all, on the immunohistochemical study the diagnosis of PEComa was retained for both lesions. In the gastrointestinal tract, the principal differential diagnoses of PEComas are gastrointestinal stromal tumors, particularly the round cell/epithelioid subtype, and metastases of carcinoma and melanoma. Other differential diagnoses include rhabdomyosarcoma, paraganglioma, leiomyosarcoma, and clear cell sarcoma.
authors.affiliation: Institut Universitaire de Pathologie, Lausanne, Switzerland. muriel.genevay@hcuge.ch
authors.forename: Muriel
authors.initials: M
authors.lastname: Genevay
authors.forename: Thomas
authors.initials: T
authors.lastname: Mc Kee
authors.forename: George
authors.initials: G
authors.lastname: Zimmer
authors.forename: Gieri
authors.initials: G
authors.lastname: Cathomas
authors.forename: Louis
authors.initials: L
authors.lastname: Guillou
mesh_terms: D000008:Abdominal Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000601:surgery; D000328:Adult; D018207:Angiomyolipoma / Q000737:chemistry / Q000175:diagnosis* / Q000601:surgery; D014408:Biomarkers, Tumor / Q000032:analysis; D002277:Carcinoma / Q000175:diagnosis / Q000556:secondary; D003937:Diagnosis, Differential; D015622:Epithelioid Cells / Q000737:chemistry / Q000473:pathology*; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000737:chemistry / Q000175:diagnosis; D006801:Humans; D007124:Immunoenzyme Techniques; D008545:Melanoma / Q000175:diagnosis / Q000556:secondary; D009363:Neoplasm Proteins / Q000737:chemistry; D010236:Paraganglioma, Extra-Adrenal / Q000175:diagnosis; D012509:Sarcoma / Q000175:diagnosis
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins