[852] Oncocytic Papillary Renal Cell Carcinoma with Inverted Nuclear Pattern: A Distinct Subtype with an Indolent Clinical Course

BH Park, KE Kim, GY Gong, YM Cho, JY Ro, WS Park, KJ Jee. Asan Medical Center, Seoul, Republic of Korea; The Methodist Hospital, Houston, TX; Natinal Cancer Center, Goyang, Republic of Korea; Haartman Institute, University of Helsinki, Helsinki, Finland

Background: Papillary renal cell carcinomas (PRCC) are the second most common renal cell carcinoma (RCC), accounting for approximately 10% of RCC. There are two types of PRCCs, which have different histologic features and clinical behavior with poorer prognosis in type 2. We present seven cases of a histologically distinct oncocytic papillary renal cell carcinoma (OPRCC) with an inverted nuclear pattern and histologic features overlapping with those of types 1 and 2 PRCC.
Design: Thirty three cases of pure PRCC were reviewed and seven cases of OPRCC with an inverted nuclear pattern were identified. We assessed their clinical and histologic features, immunohistochemical profile, and genomic aberration, in comparison with those of types 1 and type 2 PRCC. The oncocytic features was defined as abundant eosinophilic granular cytoplasm and inverted pattern as polarization of nuclei toward the surface of papillae as a single layer.
Results: The median age of the seven patients was 67 years. Grossly, tumors were well-circumscribed and small (1.2 cm 0.4 cm). Microscopically, the OPRCCs were composed of well-developed thin papillae, lined with a single layer of cuboidal-to-columnar oncocytic cells. The tumor cells had eosinophilic granular cytoplasm and round-to-oval nuclei. The nuclei were characteristically polarized toward the surface of the papillae and contained mostly small nucleoli. The tumors showed high expression of AMACR, CK7, MUC1, VEGF, E-cadherin, and CD117, low expression of CD10, and no expression of CK20. Genetically, we observed gains of chromosomes 3p, 11q, and 17q, and loss of chromosome 4q. All seven patients were alive with no recurrence or metastasis at a mean follow-up time of 37.1 23.7 months.
Conclusions: OPRCCs show unique pathologic features with indolent clinical behavior and are more similar clinicopathologically to type 1 than to type 2 PRCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 105, Tuesday Morning