[1951] Spectrum of PTEN Expression in Non-Pancreatic Gastrointestinal Neuroendocrine Tumors

Maryam J Zenali, Russell Broaddus, Ronald Bassett, Stanley R Hamilton. The University of Texas MD-Anderson Cancer Center, Houston, TX; The University of Texas MD Anderson Cancer Center, Houston, TX

Background: Loss of PTEN expression is associated with tumorigenesis in several tumor types including endometrial, prostatic and colorectal adenocarcinoma. PTEN expression profile in non-pancreatic gastrointestinal neuroendocrine tumors is unclear. In this study, we evaluated PTEN immunoreactivity in 104 neuroendocrine tumors of the foregut, midgut, and hindgut.
Design: 119 cases of non-pancreatic gastrointestinal neuroendocrine tumors were collected from the pathology archives, 2002 to 2011. Sufficient material was available in104 cases. In 37 cases both primary and metastasis and in 4 more than one primary or metastatic site were examined. Immunohistochemistry for PTEN (Dako; clone: 6H2.1; dilution 1:100) was performed and recorded as P: strong homogenous; R: reduced in more than 50%; H: heterogeneous: positive with few foci of loss; L: loss in all or in overwhelming majority.
Results: From 104 cases, 98 were low grade, 4 intermediate, and 2 high grade. Locations were ileum (74), stomach (12), colorectal (11), duodenum (4), jejunum (2), and esophagus (1). Majority were high stage (III+IV: 86/104) and 82 of 104 had positive lymph nodes. Immunohistochemical results are summarized in tables 1 and 2.

Table 1: overall immunoexpression pattern
Patterns of StainingLossHeterogeneousReducedPositive
4 patients with multiple sites examined were only used once

Table 2: Expression of PTEN in primary compared with expression in metastasis

Conclusions: Loss of PTEN was noted in high grade tumors (neuroendocrine carcinoma) (2/2, one died) and in patients with reduced survival, irrespective of grade (6 of total 9 patients, the remaining 3 showed a reduced pattern of expression). These results support role of PTEN inactivation towards aggressive behavior in non-pancreatic gastrointestinal neuroendocrine tumors. Of interest, different sites of same tumor (primary and metastasis) showed similar patterns of immunoreactivity (same pattern was observed in 28/37 pairs). We did not find statistically significant correlations between expression pattern and disease stage, lymph node status, or patient's age.
Category: Pathobiology

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 274, Wednesday Morning


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