[870] Renal Mucinous Tubular and Spindle Cell Carcinoma: Expanding Our Knowledge of Immunohistochemical and Cytogenetic Findings.

Anna R Laury, Marcela Riveros-Angel, Venkata S Sabbisetti, Paola Dal Cin, Michelle S Hirsch. Brigham and Women's Hospital, Boston, MA

Background: Mucinous tubular and spindle cell carcinoma (MTSCC) is a recently described rare subtype of renal cell carcinoma (RCC). It is a heterogenous tumor composed of epithelioid cells forming tubules and cords, admixed with spindle cell foci, typically associated with a mucinous/myxoid stroma. The differential diagnosis of MTSCC includes papillary RCC (PRCC) due to overlapping architectural and immunohistochemical findings. The few previously reported karyotypes have described multiple monosomies; however, fewer than typically seen in chromophobe RCC (ChRCC). The goal of this study was to better characterize the immunoprofile and chromosomal abnormalities (as determined by conventional karyotype and FISH) in MTSCCs, particularly as compared to PRCC, ChRCC, and oncocytoma (ONC).
Design: 22 cytogenetically confirmed renal epithelial neoplasms (5 MTSCCs, 6 PRCCs, 5 ChRCCs, & 6 ONCs) were immunostained for RCC, CK7, CK20, CD10, AMACR, hKIM-1, S100A1, Galectin3, WT1, HMB45, CD15, cKit, and E-cadherin. Staining was scored as negative (0), rare (1+, <10%) or positive (2+, 10-50% or 3+, >50%). All analyses were interpreted blind to morphologic and karyotypic diagnoses.
Results: Conventional cytogenetics demonstrated that the MTSCCs contained multiple monosomies, including losses of 1, 6, 14, 15 and 22. Positive immunohistochemical findings are presented in Table 1. The presence of Galectin3, cytoplasmic (cy) WT-1, and E-cadherin plus the absence of CD10 support the diagnosis of MTSCC over PRCC. The absence of AMACR, S100A1 and KIM-1 can help distinguish ChRCC from MTSCC when overlapping cytogenetic findings (multiple monosomies) are present; Galectin-3 is not helpful for this distinction. CK7, CK20, RCC, CD15, cKit, and HMB45 are less useful discriminators.

Neoplasm (N)Galectin3E-CadherinWT1 (cy)CD10AMACRS100A1KIM-1
MTSCCA (5)3321443
PRCC (6)0005652
ChRCC (5)5500000
ONC (6)6101050

Conclusions: This study presents the karyotypic findings of 5 additional MTSCCs, confirming that multiple chromosomal monosomies (esp. 1, 6, 14, 15, and 22) are common in MTSCC. It also demonstrates a new and unique immunohistochemical panel (Galectin3+, WT1+, E-cadeherin+/CD10-) which can aid in the diagnosis of MTSCCA over PRCC. The presence of AMACR, S100A1, and KIM-1 also support a diagnosis of MTSCC over ChRCC. FISH, in combination with morphologic and immunophenotypic findings, is predicted to aid in the diagnosis of MTSCC, especially when conventional cytogenetics is not available.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 85, Wednesday Morning


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