[795] Immunohistochemical Stain for Cytokeratin 7, S100A1, and Claudin 8 Is Valuable in Differential Diagnosis of Chromophobe Renal Cell Carcinoma from Renal Oncocytoma

SS Kim, C Choi, YD Choi. Chonnam National University Hospital, Gwangju, Republic of Korea; Chonnam National University Hwasun Hospital, Hwasun eup, Chollanamdo, Republic of Korea

Background: Some cases of chromophobe renal cell carcinomas (CRCC) have overlapping histologic features with renal oncocytoma. Although both CRCC and renal oncocytoma are originated from the intercalated cells of collecting ducts, each type has different biological behavior. We studied the difference of CK7, S100A1, and claudin 8 immunomarkers in classical chromophobe renal cell carcinoma (ChRC), renal oncocytoma (RO), and tumor of overlapping histology (TOH).
Design: We used archived specimens of 24 classical ChRCs, 25 RO, and 11 TOH. The author analyzed the immunohistochemical expressions of CK7, S100A1, and claudin-8 in differentiation of CRCC and renal oncocytoma. Based on this data we applied and analyzed immunohistochemical stain in tumors of overlapping histology.
Results: CK7 was positive in 21 out of 24 classical ChRCs, and was negative in 23 of 25 ROs. S100A1 was negative in all classical ChRCs, and was positive in 23 of 25 ROs. Claudin 8 was positive with membranous pattern in 14, and with cytoplasmic pattern in one of 24 classical ChRCs, respectively. However, it was positive with cytoplasmic pattern in 24 of 25 ROs. When the immunoreactivity of three immunomarkers are combined as a panel, classical ChRCs and ROs revealed different immunophenotypes. Accordingly, 11 TOHs could be classified as 6 ChRCs and 5 ROs. We examined 4 cases of TOH by electron microscopy, and found that the ultrastructural findings were concordant with the diagnoses based on immunophenotypes.
Conclusions: We demonstrate that classical ChRC and RO reveal very significant difference in CK7, S100A1, and claudin 8 immunoreactivity. And also suggest that a panel of three immunostains could be used to classify TOH into ChRC and RO.
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 106, Tuesday Morning