Peripheral nerve sheath tumors of the gastrointestinal tract: a multicenter study of 58 patients including NF1-associated gastric schwannoma and unusual morphologic variants

Abstract

The frequency and morphological spectrum of gastrointestinal peripheral nerve sheath tumors (PNSTs) from consecutive case material has not been studied in the c-KIT era. We reviewed all mesenchymal gastrointestinal (GI) lesions at our departments according to current diagnostic criteria. PNSTs formed the third commonest group of mesenchymal GI tumors with a lower frequency (< or =5%) compared to gastrointestinal stromal tumors (GISTs; approximately 50%) and smooth muscle neoplasms ( approximately 30%). Granular cell tumors (GCTs; n = 31) and schwannomas (n = 22) were the most common types of PNSTs encountered. Rare tumors included neurofibromatosis 1 (NF1)-associated PNSTs (n = 5) and gastric perineurioma (n = 1). Thirteen schwannomas (including also some recent cases) were initially diagnosed as GIST, leiomyoma, or neurofibroma. Unusual histological variants included sigmoid GCT with prominent lipomatous component (n = 1), reticular-microcystic schwannoma of small (n = 1) and large (n = 1) bowel, NF1-associated gastric schwannoma (the first case to date), and psammomatous melanotic colonic schwannoma unrelated to Carney complex (n = 1). PNSTs coexisted with GIST in four patients (three had definite NF1). In conclusion, PNSTs of the GI tract are rare uniformly benign neoplasms that may show schwannian, perineurial, fibroblastic, or mixed differentiation. Most of them (92%) occurred sporadically unassociated with NF1 or NF2. Gastrointestinal PNSTs are still underrecognized by general pathologists. Awareness of their diverse morphology will help to avoid confusing them with smooth muscle neoplasms and GIST that they may closely mimic.

Case report of unusual cause of lower GI bleeding

“…The mean age at GIST diagnosis was 49 years compared to a mean age of 56 years for small bowel GISTs in genera l. Most NF-1 associated GISTs present as small asymptomatic lesions with low mitotic activity and they generally follow a benign clinical course [8,9].…”

Ileal perineurioma as a cause of intussusception

“…4 Very few reports of perineuriomas arising in the gastrointestinal tract have been published. [5][6][7][8][9][10] Hornick et al 5 first described perineuriomas of the intestine. They presented 10 cases of intestinal perineuriomas, of which nine were located in the colon and one in the jejunum, with no cases located in the ileum.…”

“…2 Perineuriomas have also been reported in unusual locations such as the kidneys 3 and the paratesticular region. 4 Very few reports [5][6][7][8][9][10] have described perineuriomas in the gastrointestinal tract, and these have mainly been in the stomach, colon and jejunum. We report the clinicopathological and immunohistochemical features of a case of ileal perineurioma, of soft-tissue type, manifested clinically through intestinal obstruction due to intussusception.…”

Microcystic/Reticular Schwannoma of the Proximal Sigmoid Colon: Case Report With Review of Literature

“…Even conventional gastrointestinal schwannomas occur sparingly and tend to localize in the stomach. 3 The recently described microcystic/reticular variant is more common in the large intestine. Only 2 of the 12 cases reported so far have occurred in the stomach.…”

“…This series included 5 cases located in the gastrointestinal tract; the remaining 5 cases were located in the bronchial wall, left adrenal gland, right arm, and subcutaneous tissue of the back and within the muscle of the upper back. Subsequently to that series, 7 more cases [3][4][5][6] of this variant involving the luminal gastrointestinal tract have been described. Adding to these recent publications, we report another example of this rare variant that was initially identified in our department well before publication of the 2008 series 2 and describe for the first time to our knowledge ultrastructure findings and significant differential diagnostic considerations.…”