title: Diffuse intra-abdominal clear cell myomelanocytic tumor: report of an unusual presentation of "PEComatosis" simulating peritoneal mesothelioma.
abstract: We report a case of diffuse myomelanocytic tumor of the peritoneum that simulates, clinically and instrumentally, a malignant mesothelioma. The patient was a 70-year-old woman with a history of ancient hysterectomy for fibroids, who presented with abdominal discomfort. Exploratory laparotomy revealed diffuse encasing of the peritonealized organs by a thin, fleshy, gray-white tissue rind. Scattered tumor masses were present as well. A dominant lesion measuring 6 cm in larger size was resected from the pelvis. Histological examination revealed a tumor composed of epithelioid and spindle cells, exhibiting either a clear or slightly eosinophilic cytoplasm and a mild to moderate nuclear pleomorphism. Focal areas of necrosis could be documented. Immunohistochemically, tumor cells were positive for HMB45, melan-A, and smooth muscle actin, but negative for other antibodies, including epithelial markers, desmin, and S100 protein. We believe that this case represents an example of myomelanocytic tumor of uncertain biologic potential, a member of the recently devised perivascular epithelioid cell tumors (PEComa), with an unusual presentation simulating a diffuse mesothelial neoplasm. The origin of this particular lesion is briefly discussed in light of the recent literature published on the subject.
authors.affiliation: Department of Anatomic Pathology, City Hospital, I 35013 Cittadella, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Salviato
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Altavilla
authors.forename: Graziella
authors.initials: G
authors.lastname: Busatto
authors.forename: Stefano
authors.initials: S
authors.lastname: Pizzolitto
authors.forename: Giovanni
authors.initials: G
authors.lastname: Falconieri
mesh_terms: D000008:Abdominal Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D000368:Aged; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor / Q000032:analysis; D049109:Cell Proliferation; D003937:Diagnosis, Differential; D015622:Epithelioid Cells / Q000737:chemistry / Q000473:pathology*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D019394:Ki-67 Antigen / Q000032:analysis; D018230:Leiomyoma, Epithelioid; D058950:Melanoma-Specific Antigens; D008654:Mesothelioma / Q000175:diagnosis*; D009363:Neoplasm Proteins / Q000032:analysis; D010534:Peritoneal Neoplasms / Q000175:diagnosis*; D018235:Smooth Muscle Tumor / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins