title: Malignant pigmented clear cell epithelioid tumor of the kidney: clear cell ("sugar") tumor versus malignant melanoma.
abstract: A 73-year-old woman presented with an hemorrhagic kidney tumor initially interpreted as a renal cell carcinoma (RCC). A retroperitoneal recurrence infiltrating the duodenal wall was made up of clear cells, some of which contained Fontana-Masson positive pigment, immunopositive for HMB-45, S-100 protein, actin, and vimentin. The same immunohistochemical profile was retrospectively reproduced in the kidney tumor, where melanosomes were also found ultrastructurally. Lipomatous differentiation was not observed. There was no history of malignant melanoma (MM), or stigmata of tuberous sclerosis. The patient died of disease 5 years after the initial diagnosis. This neoplasm can be considered as a malignant, pigmented, clear-cell epithelioid variant of angiomyolipoma, or "sugar" tumor of the kidney, with the peculiarity of having a previously unreported component of pigmented cells visible on light microscopy. This finding raises the possibility that the exceptional cases of MM reported in renal parenchyma may be pigmented variants of epithelioid angiomyolipoma rather than true MM.
authors.affiliation: Department of Pathology of the Hospital Clínic, Facultat de Medicina de la Universitat de Barcelona, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Ribalta
authors.forename: J
authors.initials: J
authors.lastname: Lloreta
authors.forename: A
authors.initials: A
authors.lastname: Munné
authors.forename: S
authors.initials: S
authors.lastname: Serrano
authors.forename: A
authors.initials: A
authors.lastname: Cardesa
mesh_terms: D000368:Aged; D018207:Angiomyolipoma / Q000737:chemistry / Q000175:diagnosis* / Q000601:surgery; D014408:Biomarkers, Tumor / Q000032:analysis; D002292:Carcinoma, Renal Cell / Q000175:diagnosis; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007680:Kidney Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000601:surgery; D008545:Melanoma / Q000737:chemistry / Q000175:diagnosis* / Q000601:surgery; D020460:Melanosomes / Q000648:ultrastructure; D009364:Neoplasm Recurrence, Local / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor