[915] Renal Small Cell Oncocytoma with Pseudosettes – A Histomorphologic, Immunohistochemical, Ultrastructural and Molecular Genetic Study of 10 Cases.

Fredrik B Petersson, Tomas Vanecek, Michal Michal, Naoto Kuroda, Milan Hora, Ondrej Hes. Charles University and University Hospital, Plzen, Czech Republic; National University Health System, Singapore, Singapore; Red Cross Hospital, Kochi, Japan

Background: A clinicopathological characterization of a rare subtype of renal oncocytoma (RO), the small cell oncocytoma with pseudorosettes (SCOP) is presented. This subset of SCO may present differential diagnostic problems, especially on core biopsies.
Design: 10 cases of SCOP were identified out of 391 ROs from our registry. Detailed morphologic immunohistochemical studies and molecular genetic (FISH and CGH) analyses were performed.
Results: The cohort comprised of 6 females and 4 males, age 51 to 84 years. The tumors were composed of small basophilic cells (“oncoblasts”) with scant cytoplasm and monomorphic nuclei. No necrosis or mitotic activity were discerned. In all cases, a varying number of pseudorosettes were identified. The pseudorosettes were composed of small globules of (PAS-positive) hyaline basal membrane-like material surrounded by small oncoblastic cells. The immunohistochemical profile of the neoplastic cells was: positivity for AE1-3 (10/10), EMA (10/10), c-kit (6/10), MIA, Pax 2 (9/10), AMACR (6/10), CD10 (5/10), parvalbumin (8/10), claudin 7 (10/10) and claudin 8 (3/10). No immunoreactivity for carbonic anhydrase IX, HMB-45, S100A1, TFE3. Using CGH, no chromosomal changes were identified in 3 examined cases. No numerical changes of chromosomes 7 and 17 were revealed on FISH analysis.
Conclusions: 1, SCOP constitute a morphologically homogenous subset of tumors group within SCOs. 2, The immunohistochemical profile of SCOP was variable and differed in significant respects from that of conventional renal oncocytoma. 3, No genetic abnormalities were detected on CGH analysis. 4, All tumors behaved in a benign fashion.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 90, Wednesday Morning


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