[1170] The Lung-Restricted Marker Napsin A Is Highly Expressed in Clear Cell Carcinomas of the Ovary

Patricia L Kandalaft, Christina Isacson, Allen M Gown. PhenoPath Laboratories, PLLC, Seattle, WA; CellNetix Pathology and Laboratories, Seattle, WA; IMPRIS, Seattle, WA

Background: Napsin A is a member of the aspartic proteinase family that is expressed at high levels in type II pneumocytes and pulmonary macrophages and has been recently demonstrated to be a relatively specific and sensitive marker of lung adenocarcinomas. However, napsin A expression has also been identified in a subset of renal papillary and clear cell carcinomas, as well as a small number of thyroid carcinomas. Recently, we identified expression of napsin A in a case of clear cell carcinoma (CCCa) of ovary and, therefore, wished to determine the extent of napsin A in a series of CCCas, comparing results with other gynecologic tract (GYN tract) carcinomas, including endometrioid adenocarcinomas (EnCa) and high grade papillary serous carcinomas (PSCa) of ovary.
Design: A series of 12 CCCa, 10 EnCa and 10 PSCa were tested by immunohistochemistry (IHC) with a monoclonal antibody to napsin A (IP64, Leica), comparing results with antibodies to another lung-restricted marker, TTF-1 (SPT24, Leica), and a GYN-restricted marker, PAX8 (BC12, Biocare). The following scoring criteria were employed: 0 = negative, <1% = rare cell, 1-25% = focal, 26-75% = variable, and >75% = uniform.
Results: All 12 of 12 (100%) of CCCas were napsin A-positive, with all 12 cases showing variable to uniform expression. In contrast, 3/11 (27%) of EnCa, 0/10 (0%) of PSCa were napsin A-positive. The lung-restricted marker, TTF-1, was positive in 0/12 (0%) of CCCa, 1/11 (9%) EnCa, and 1/10 (10%) PSCa, usually either rare cells positive or focally positive. The GYN-restricted marker, PAX-8, was positive in 9/9 (100%) CCCa, 9/10 (90%) EnCa, and 10/10 (100%) PSCa; all cases were uniformly positive.
Conclusions: Napsin A is highly expressed in clear cell carcinomas of ovary, occasionally expressed in endometrioid adenocarcinomas and not expressed in serous papillary carcinomas. This unexpected finding suggests that napsin A may assist in separating CCCa from its mimics in GYN tract and could prove critical in the evaluation of metastatic carcinomas of unknown primary in which ovarian carcinoma is in the differential diagnosis. A potential pitfall, however, could be the rare case of TTF-1-positive/napsin A-positive endometrioid adenocarcinoma. These findings underscore the importance of using a complete antibody panel to include multiple “organ-specific” markers in identifying carcinomas of unknown primaries.
Category: Gynecologic & Obstetrics

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 147, Tuesday Afternoon


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