title: Pseudosarcomatous fibroblastic/myofibroblastic proliferation in perinephric adipose tissue adjacent to renal cell carcinoma: a lesion mimicking well-differentiated liposarcoma.
abstract: Cytologically atypical stromal cells were found in the perinephric adipose tissue, mimicking well-differentiated liposarcoma in 12 of 59 (20%) consecutive nephrectomy specimens that were resected for renal cell carcinoma. Morphologically, the atypical cells included enlarged, hyperchromatic spindle cells and floret-type multinucleate cells. Of 59, 10 (17%) renal cell carcinomas invaded through the renal capsule into the perinephric adipose tissue. Of these cases, three (30%) contained the aforementioned atypical cells. In contrast, 9 of 49 cases without extrarenal invasion (18%) contained the atypical stromal cells. Of the 12 cases with atypical stromal cells, 3 (25%) were associated with extrarenal involvement. The atypical spindle cells exhibited focal to variable positivity for smooth muscle actin and desmin in 3 of the 14 cases (including two cases from our consultation files) each. Cytokeratin AE1/AE3, cytokeratin Cam 5.2, cytokeratin 7, epithelial membrane antigen, and S-100 were negative in all cases. Amplification of MDM2 gene region, which is commonly observed in well-differentiated liposarcoma, was absent by fluorescence in situ hybridization (FISH) in the atypical stromal cells. Immunohistochemistry and FISH suggest that the atypical cells are most consistent with reactive fibroblasts/myofibroblasts. Recognition of these atypical fibroblasts/myofibroblasts may help in avoiding the potential pitfall of misdiagnosing them as well-differentiated liposarcoma.
authors.affiliation: Department of Anatomic Pathology, Pathology and Laboratory Medicine Institute, The Cleveland Clinic and The Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA.
authors.forename: Munir R
authors.initials: MR
authors.lastname: Tanas
authors.forename: Chalenpoj
authors.initials: C
authors.lastname: Sthapanachai
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nonaka
authors.forename: Jonathan
authors.initials: J
authors.lastname: Melamed
authors.forename: Andre M
authors.initials: AM
authors.lastname: Oliveira
authors.forename: Michele R
authors.initials: MR
authors.lastname: Erickson-Johnson
authors.forename: Brian P
authors.initials: BP
authors.lastname: Rubin
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D014408:Biomarkers, Tumor / Q000032:analysis; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000473:pathology*; D003937:Diagnosis, Differential; D005347:Fibroblasts / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D008080:Liposarcoma / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor