Colonic perineurioma (benign fibroblastic polyp): case report and review of the literature

A Case of Multiple Perineuriomas in the Colon With Underlying Neurofibromatosis Type I

A 45-year-old woman was referred to us after a positive fecal occult blood test. Colonoscopy revealed a 20-mm polyp in the transverse colon and a 10-mm polyp in the sigmoid colon. Endoscopic mucosal resection was performed as a diagnostic treatment. Both resected polyps were histologically diagnosed as perineuriomas. She was later found to exhibit multiple café-au-lait spots on the skin and subsequently diagnosed as having neurofibromatosis type I (NF-1). Perineuriomas are rare benign peripheral nerve sheath tumors, with no reports of multiple colonic lesions in a patient with NF-1 to date. NF-1 might be associated with the onset of multiple perineuriomas.

Epithelial-Stromal Polyps of the Colon Are Not Perineuriomas

OBJECTIVES

Some colorectal polyps contain serrated or tubular crypts surrounded by whorls of spindle cells that expand the mucosa. These epithelial-stromal polyps have been termed benign fibroblastic polyps or, more commonly, perineuriomas. We hypothesized that these lesions are pathogenetically heterogeneous polyps that share in common exuberant fibroblastic proliferations derived from the pericryptal sheath.

METHODS

Forty-six epithelial-stromal polyps containing serrated crypts (n = 21) and nonserrated crypts (n = 25) were evaluated with epithelial membrane antigen and BRAF V600E immunohistochemical stains, and a subset was subjected to next-generation sequencing for BRAF mutations. Polyp morphology and immunohistochemical results were correlated with clinical information.

RESULTS

Epithelial-stromal polyps containing serrated crypts were significantly associated with other sessile serrated polyps (43%, P = .01) and hyperplastic polyps (29%, P = .006). They also showed BRAF V600E abnormalities (95%) and strong, patchy epithelial membrane antigen staining of spindle cells (95%). In contrast, polyps with nonserrated crypts lacked BRAF alterations and infrequently showed robust EMA staining of stromal cells (16%, P < .01).

CONCLUSIONS

Benign epithelial-stromal polyps with serrated epithelium are biologically similar to sessile serrated polyps and should be classified as such to ensure appropriate clinical surveillance. The nature of polyps without serrated crypts is less clear, but evidence that they are perineuriomas is circumstantial at best.

A Solitary Sigmoid Perineurioma in an Otherwise Healthy 30-Year-Old Male

Colorectal perineuriomas are rare benign fibroblastic polyps of the colon found on colonoscopy and usually present as a sessile polyp distal to the splenic flexure. We report a case of sessile sigmoid perineurioma in a young healthy male. He presented with chronic constipation and underwent colonoscopy, which showed a 3-4 mm sessile polyp in the sigmoid colon. Biopsy results were significant for a perineurioma. These polyps are peripheral nerve sheath tumors composed of bland spindle cells with ovoid nuclei in a whorling appearance. The differential diagnosis of these nerve sheath tumors includes ganglioneuromas, schwannomas, neuromas, neurofibroma, or Schwann cell hamartomas, and gastrointestinal stromal tumor (GIST). While these polyps are regarded as benign, it is prudent to rule out other tumors that have malignant potential.

Cap-assisted Endoscopic Mucosal Resection of Rectal Perineurioma Mimicking a Neuroendocrine Tumor

Colorectal perineuriomas are benign mucosal-based mesenchymal tumors composed of perineurial cells and show serrated or hyperplastic crypts in epithelium on histopathological evaluation. Most perineuriomas are usually presented as sessile polyps and often as subepithelial tumors. In this case, colonoscopy revealed a rectal subepithelial tumor (measuring approximately 7 mm) with yellowish- colored normal mucosa. A rectal neuroendocrine tumor was suspected, and cap-assisted endoscopic mucosal resection was performed. Histopathological examination of the resected specimen revealed bland spindle cells showing immunopositivity for CD34. The patient was finally diagnosed with rectal perineurioma.

Spindle cell proliferations of the sigmoid colon, rectum and anus: a review with emphasis on perineurioma

A wide range of spindle cell proliferations are found uncommonly in the sigmoid colon, rectum and anus. They usually present as polyps, and include reactive lesions and benign and malignant neoplasms which may be primary or metastatic. They are less frequently described in the literature compared to those in the upper gastrointestinal tract, and may be underdiagnosed. The widespread use of sigmoidoscopy in symptomatic patients and bowel cancer screening programmes means that histopathologists must be aware of, and adopt a logical approach to, diagnosing spindle cell proliferations in biopsy and polypectomy specimens. This is particularly relevant given the strong association of some mesenchymal polyps with hereditary cancer syndromes. This review article will focus on perineurioma and the recent debate in relation to its overlap with fibroblastic polyp. The clinical, endoscopic, histological and immunohistochemical features of spindle cell proliferations which should be considered in the differential diagnosis of perineurioma will be discussed. There is also a brief reference to malignant spindle cell tumours of diagnostic importance.

Colonic Perineurioma's Malignant Proximity to Serrated Colonic Polyps

A colonic perineurioma is often considered a benign cousin to a colonic polyp. However, in the submucosal type of perineurioma, it is important to rule out the malignant gastrointestinal stromal tumor (GIST). Alternatively, in the BRAF-positive serrated types of perineuriomas, surveillance is equivalent to intervals designated to serrated polyps due to a similar malignant potential. These versions serve as reminders that colonic perineuriomas are not to be disregarded.

Intramucosal fat is uncommon in large bowel polyps but raises three differential diagnoses

AIMS

This case series intends to expand currently limited knowledge regarding the existence and diagnostic significance of intramucosal fat in colorectal polyps.

METHODS

Clinicopathological features of nine such polyps were reported following histopathological review, including S100 and EMA immunohistochemistry.

RESULTS AND CONCLUSIONS

Such review subdivided seven polyps into three groups: (1) mucosal perineurioma/serrated polyps with fat among the perineurial stroma (three cases); (2) submucosal lipomas with adipose tissue extending into the overlying mucosa (two cases) and (3) polyps with intramucosal adipose tissue only, that is, the newly described but less-recognised entity known as intramucosal lipoma (two cases). The two remaining polyps of this series did not include submucosa but, from assessing their muscularis mucosae, were favoured to represent intramucosal lipomas. The first two phenomena are formally described for the first time by this case series. The last of these three diagnoses should prompt investigations for Cowden syndrome, but intramucosal lipomas are more often sporadic/non-syndromic.

A Colonic Perineurioma

Perineurioma is a mesenchymal neoplasm best known in soft-tissue pathology. A colonic perineurioma is a relatively recently described entity and sometimes encountered in specimens from the large intestine, especially distal colon. Without its recognition, a perineurioma can be misdiagnosed as other more common gastrointestinal spindle cell neoplasms. Here, we describe a case of colonic perineurioma with polypoid growth extruding into the intestinal lumen. Case. A woman in her seventh decade of life underwent a follow-up colonoscopy after an uneventful resection of a benign colonic polyp. A previously undetected 6-mm polyp was found in the sigmoid colon and was resected endoscopically. Microscopic examination of the lesion revealed a proliferation of bland spindle cells in the lamina propria mucosae, which were immunohistochemically positive for epithelial membrane antigen, claudin 1, and glucose transporter-1. A colonic perineurioma was diagnosed.