[769] High Grade Neuroendocrine Carcinoma of the Anorectum: A Clinicopathologic Study of 7 Cases of a Rare Entity

Homer Wiland, Robert Odze, Stephanie Schulte, John R Goldblum. Cleveland Clinic Foundation, Cleveland, OH; Brigham and Women's Hospital, Boston, MA

Background: High grade neuroendocrine carcinomas (HGNEC) of the gastrointestinal tract are uncommon and may be classified as small cell or large cell type. Given their therapeutic and prognostic implications, it is imperative to establish an accurate diagnosis by histology and immunohistochemistry in order to rule out tumors that may mimic HGNEC. The aim of this study was to evaluate the clinical and pathologic features and outcome of 7 cases of anorectal HGNEC.
Design: Seven cases were obtained by searching the pathology files at two major medical institutions, indicating the rarity of this tumor. Clinical records were assessed for treatment and outcome. We examined many features such as the type of HGNEC (small vs large cell) and the presence or absence of anal intraepithelial neoplasia (AIN) and/or adenomatous changes, among others. All cases were evaluated for synaptophysin, chromogranin, CDX2, p63, and cytokeratin 5/6 expression.
Results: Four cases were large cell NEC and 3 were small cell carcinoma. Two cases revealed a second type of carcinomatous component (1 adenocarcinoma and 1 squamous cell carcinoma), one case had an adenomatous component with high grade dysplasia; no cases demonstrated evidence of AIN. Immunohistochemically, the large/small cell components of the tumors stained for synaptophysin (6/7), chromogranin (5/7), CDX 2 (1/7, focal weak), and CK 5/6 (1/7, focal weak). All cases were negative for p63. All patients were treated with adjuvant chemoradiation with platinum-based chemotherapy for metastatic disease. Four patients died of disease within 2 years of treatment, 2 patients were lost to follow-up, and one patient is alive ten years following diagnosis and currently stable on chemotherapy.
Conclusions: HGNECs of the anorectum are rare, as only 7 cases were identified in the pathology files at two major medical institutions. Correct diagnosis of these tumors is critical given their therapeutic and prognostic implications. Our study suggests that HGNECs of the anorectum may be associated with non-neuroendocrine carcinomatous components. In our experience, such tumors are treated similarly to pure HGNECs.
Category: Gastrointestinal

Monday, March 19, 2012 1:00 PM

Poster Session II # 126, Monday Afternoon


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