Article

Fibroblastic polyp of the colon shares features with Vanek tumor.

American Journal of Surgical Pathology (Impact Factor: 4.59). 11/2004; 28(10):1397-8; author reply 1398.
Source: PubMed
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    ABSTRACT: Colorectal perineuriomas are characterized by a mucosal proliferation of benign stromal cells expressing perineurial markers leading to separation and/or disorganization of the crypts that frequently display a serrated/hyperplastic architecture. Previous studies demonstrated a high prevalence of a BRAF p.V600E mutation in perineuriomas with serrated crypts and suggested that perineuriomas without crypt serration may represent an unrelated, different type of polyp. Yet, these molecular analyses included only 2 cases of perineuriomas without crypt serration. In fact, no previous studies can be found in the literature that have separately analyzed serrated and nonserrated perineuriomas and made a comparison between them. We retrospectively evaluated the clinical, histologic, immunohistochemical, and molecular features of 15 perineuriomas without and 45 with crypt serration (NSPs and SPs, respectively). No significant differences were found between the groups with regard to sex, age, location, and size. Histologically, the perineurial proliferation in SPs and NSPs demonstrated similar features with fascicles or bundles of bland, plump spindle cells surrounding and separating the crypts. All lesions showed expression with at least 2 of 4 perineurial cell markers (epithelial membrane antigen, claudin-1, GLUT-1, and collagen type IV). Molecular analysis performed in 20 cases (8 SPs and 12 NSPs) identified BRAF mutation of codon 600 in 5 (62%) SPs including 3 with p.V600E (c.1799T>A) and 2 with p.V600R (c.GT1798_99GT>AG). In contrast, no case of NSPs harbored BRAF mutations (p value 0.004). Our findings confirm that BRAF mutations originate in the serrated epithelium of SPs and demonstrate that SPs and NSPs have similar clinical and endoscopic characteristics and similar stroma, suggesting that they might represent 2 variants of a single lesion.
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    ABSTRACT: Fibroblastic polyps of the colon and intestinal perineuriomas are unusual mucosal lesions with identical clinical and histologic features, and apparent different immunohistochemical and ultrastructural characteristics. However, immunohistochemical distinction was solely based on the results obtained with epithelial membrane antigen (EMA), an antibody whose reactivity on perineuriomas is difficult to demonstrate. Likewise, accurate ultrastructural diagnosis may be flawed by sampling error, preservation artifacts, or paucity of specific diagnostic features. In a recent short communication, it was suggested that both lesions may represent the same entity. To further evaluate this hypothesis, 28 colorectal polyps with clinical and histologic features of colonic fibroblastic polyps/perineuriomas (including 10 cases previously reported as fibroblastic polyps) were stained immunohistochemically for 4 markers of perineurial differentiation, that is, claudin-1, GLUT-1, collagen type IV, and EMA (the latter performed using an extended protocol for antigen retrieval and a kit for signal amplification). In addition, electron microscopy was performed in 4 cases. EMA and claudin-1 stained 26 of 28 (93%) polyps whereas GLUT-1 and collagen type IV were expressed in all of them. EMA reactivity was mostly focal and weak whereas the other markers displayed a diffuse and strong signal. Ultrastructural examination revealed elongated cells with features of perineurial differentiation including long, slender cytoplasmic processes with pinocytotic vesicles and an external lamina. Our findings support the hypothesis that fibroblastic polyps and perineuriomas of the colon represent the same entity. We suggest reclassifying fibroblastic polyps reactive to perineurial markers as perineuriomas. To reach an accurate diagnosis, we recommend employing at least 2 markers of perineurial differentiation, and performing EMA immunostaining with high antibody concentration, prolonged incubation time, and/or extended protocol for antigen retrieval.
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