Crystalloid formation in gastrointestinal schwannoma

Gastric schwannoma: a benign tumour often mistaken clinically, radiologically and histopathologically for a gastrointestinal stromal tumour--a case series

INTRODUCTION

Gastric schwannomas are rare mesenchymal tumours that arise from the nerve plexus of the gut wall. They present with non-specific symptoms and are often detected incidentally. Pre-operative investigation is not pathognomonic and many are therefore diagnosed as gastrointestinal stromal tumours (GISTs). Operative resection is usually curative as they are almost always benign, underpinning the importance of differentiating them from GISTs.

METHODS

Three cases of gastric schwannomas were identified over a seven-year period. The clinical details and management were reviewed retrospectively.

RESULTS

There were two women and one man with a mean age of 62 years (range: 51–69 years). Two patients presented with bleeding and one with abdominal pain. The mean tumour size was 5.2cm (range: 2–10cm) and the tumours were resected completely following total or wedge gastrectomies. Histology in all cases showed spindle cells with a cuff of lymphoid tissue. Immunohistochemistry confirmed positive S100 staining and negative CD117 and DOG-1 staining in all cases.

CONCLUSIONS

We report our experience with these unusual primary stromal tumours of the gut and their presentations, preoperative investigations, operative findings and pathological findings are discussed. Operative resection in all cases has been considered curative, which is supported by previous series confirming the excellent prognosis of gastric schwannomas.

Intraabdominal schwannomas: a single institution experience

INTRODUCTION

Intraabdominal schwannomas are rare, benign tumors. This study presents a single institution experience with 12 such tumors.

METHODS

Between 1991 to 2006, 12 patients with a pathologically proven intraabdominal schwannoma were identified from a series of 216 mesenchymal tumors and were reviewed retrospectively.

RESULTS

There were nine females and three male patients with a median age of 58 years (range 35-88 years). Eleven patients were symptomatic, and the tumors were located in the stomach (n = 8), jejunum, colon, rectum, and lesser sac. Multiple preoperative investigations including endoscopies with biopsies and computed tomography (CT) scans were performed, but none yielded a correct definitive preoperative diagnosis. The median tumor size was 52 mm (range 18-95 mm). Pathological examination demonstrated the 11 gastrointestinal tract (GIT) schwannomas to be solid homogenous tumors, which were highly cellular and were composed of spindle cells with positive staining for S100 protein. The pathological appearance of the lesser sac schwannoma was distinct as it demonstrated cystic degeneration with hemorrhage and Antoni A and B areas on microscopy typical of soft tissue schwannomas. All 12 patients were disease-free at a median follow-up of 22 months (range 1-120 months).

CONCLUSION

Intraabdominal schwannomas are rare tumors, which are most frequently located within the GIT. GIT schwannomas are difficult if not impossible to diagnose preoperatively as endoscopic and radiologic findings are nonspecific. The treatment of choice is complete surgical excision because of diagnostic uncertainty, and the long-term outcome is excellent as these lesions are uniformly benign.

Tactile-like corpuscles in gastric mucosa: a case report

Background

The presence of tactile corpuscle-like structures in Schwannomas, Neurofibromas and Neuroid Intradermal Melanocytic Nevi is well-documented. We report a case describing the presence of such structures in the lamina propria of grossly normal gastric mucosa.

Case presentation

A 30 year-old male underwent esophagogastrectomy for carcinoma. Examination of hematoxylin and eosin stained sections reveal tactile corpuscle-like structures in the mucosa adjacent to the main tumor mass.

Conclusion

This is a rare phenomenon and a literature search revealed only one paper describing such structures in the benign colonic mucosa of a colectomy done for carcinoma. We did not come across any cases in the literature describing such structures in gastrointestinal specimen resected for reasons other than carcinoma. To our knowledge this would be the first case reporting the existence of tactile corpuscles-like structures in gastric mucosa.

Schwannoma of the gastrointestinal tract: a clinicopathological, immunohistochemical and ultrastructural study of 33 cases

AIMS

Thirty-three cases of gastrointestinal schwannomas were analysed to elucidate their peculiar clinicopathological, immunohistochemical and ultrastructural features.

METHODS AND RESULTS

The patients were 16 men and 17 women, whose ages ranged from 27 to 81 years (median 52.6 years). Tumour size ranged from 10 to 120 mm in diameter. Follow-up in 23 cases from 6 months to 13 years showed no recurrences or metastases. Microscopically, all tumours were composed of spindle cells with focal epithelioid cells in four cases. In all cases except one, there were peripheral cuff-like lymphoid aggregates. Immunohistochemically, tumours were strongly positive for S100 protein and vimentin, the tumours were variably positive for nestin (78.8%, 26/33) and glial fibrillary acidic protein (63.6%, 21/33), three tumours had CD34+ cells, but all were negative for CD117, alpha-smooth muscle actin and desmin. Ultrastructurally, the tumours were composed of elongated spindle shaped cells with prominent parallel membranous structures.

CONCLUSIONS

Gastrointestinal schwannomas have characteristic histological features, especially the presence of a lymphoid cuff, that are different from their soft tissue and central nervous system counterparts. Gastrointestinal tract schwannomas behave in a benign fashion.

Evaluation of NF2 and NF1 tumor suppressor genes in distinctive gastrointestinal nerve sheath tumors traditionally diagnosed as benign schwannomas: s study of 20 cases

A significant percentage of conventional schwannomas, whether sporadic or associated with neurofibromatosis 2 (NF2), show loss of heterozygosity (LOH) at NF2 and/or NF2 inactivating mutations. Similarly, a significant percentage of neurofibromas show LOH at NF1 and/or NF1 inactivating mutations. There are no molecular genetic data on gastrointestinal (GI) nerve sheath tumors traditionally diagnosed as benign schwannomas, rare neoplasms possibly derived from the schwannian elements dispersed between the smooth muscle fibers. In this study, we analyzed 1 esophageal, 16 gastric, 1 small intestinal, and 2 colonic tumors of such type. Histologically, all were spindle cell neoplasms positive for S-100 protein, vimentin, and glial fibrillary acidic protein, and negative for smooth muscle markers, KIT, CD34, neurofilament proteins, and HMB45. Focal or extensive lymphoid cuffs, often containing germinal centers, were present in most cases. None of the patients had NF2 or NF1. Chromosomes 22 and 17, particularly NF2 and NF1 loci, were analyzed for LOH in all GI tumors and for comparative purposes in 10 conventional schwannomas. LOH on 22q was seen in 40% of conventional schwannomas but in only 5% (1 of 20) of GI schwannomas. PCR amplification followed by direct sequencing of PCR products failed to identify mutations in NF2 coding sequences (exons 1-15) in 13 cases, including a case with LOH on 22q. Losses on 17q involving NF1 were seen in both GI and conventional schwannomas in 50% and 33% of analyzed tumors, respectively. LOH at NF1 might be one of the genetic features seen in peripheral nerve sheath tumors from different locations and should be interpreted with caution. However, lack of NF2 alterations strongly supports the hypothesis that GI schwannomas represent a morphologically and genetically distinct group of peripheral nerve sheath tumors that are different from conventional schwannomas.

Schwannomas of the gastrointestinal tract: clinicopathological features of 12 cases including a case of esophageal tumor compared with those of gastrointestinal stromal tumors and leiomyomas of the gastrointestinal tract

We analyzed the clinicopathological features of 12 gastrointestinal (GI) schwannomas and compared them with those of 37 GI stromal tumors (GISTs) and 15 leiomyomas. Grossly, the schwannomas showed rubbery to firm, yellow-white to tan, glistening, and often trabeculated cut surfaces, resembling soft tissue schwannomas. The GISTs were firm to soft or fish-flesh tan, gray-pink, or variegated tumors with a degenerative change, and the leimyomas resembled typical uterine leiomyomas. Histologically, GI schwannomas were moderately cellular tumors with focal significant nuclear pleomorphism and rare mitotic figures. A characteristic peripheral lymphoid cuff was observed in all cases, but was indistinct in two cases. The GISTs were highly cellular spindle cell, epithelioid or, occasionally, pleomorphic tumors with basophilic appearance. Leiomyomas were paucicellular tumors with eosinophilic appearance. Immunohistochemically, schwannomas were S-100 protein- and glial fibrillary acidic protein (GFAP)-positive, but were negative for c-kit, CD34, and smooth muscle actin (SMA). GISTs were all c-kit- and/or CD34-positive, but GFAP-negative. Leiomyomas were SMA-positive and were negative for c-kit, CD34, S-100 protein, and GFAP. The mean Ki-67 index of schwannoma was 0.7, and those of GIST and leiomyoma were 5.9 and 0.3, respectively. The patients with schwannomas and leiomyomas had a favorable outcome, whereas 12 patients with GISTs showed progression and died of disease. The separation of GISTs from schwannomas is clinically important because the former group has a high risk of malignant behavior. GI schwannomas differed from the conventional soft tissue schwannomas in that they had peripheral lymphoid cuffs, lacked fibrous capsule and vascular hyalinization, and rarely showed degenerative changes. GI schwannomas, however, resembled soft tissue schwannomas in many aspects, and the clinical, gross, histological, and immunohistochemical features were different from those of GISTs and leiomyomas.

Intra-abdominal spindle cell lesions: a review and practical aids to diagnosis

Intra-abdominal spindle cell lesions are uncommon and often present a diagnostic challenge. An important group of such lesions are the gastrointestinal stromal tumours. Other intra-abdominal spindle cell lesions include fibromatosis, various sarcomas-in particular, leiomyosarcoma, liposarcoma, and malignant peripheral nerve sheath tumour-and, in women, endometrial stromal sarcoma. Less common lesions are inflammatory myofibroblastic tumours, the mesenteric spindle cell reactive lesions, retroperitoneal fibrosis, and solitary fibrous tumour. A variety of intra-abdominal tumours of nonmesenchymal origin may have a spindle cell/sarcomatoid morphology; these include sarcomatoid carcinoma, malignant melanoma and, in women, sarcomatoid granulosa cell tumour. Finally, metastatic sarcomas from pelvic or extra-abdominal organs need also be considered. A set of practical aids to the diagnosis of intra-abdominal spindle cell lesions is presented to assist pathologists dealing with such lesions, particularly with regards to the consideration of differential diagnoses.

Benign schwannoma of the digestive tract: a clinicopathologic and immunohistochemical study of five cases, including a case of esophageal tumor

We report five cases of schwannomas of the digestive tract. The patients were two men and three women, whose ages ranged from 56 to 74 years. Three cases arose in the stomach, one in the ascending colon, and one in the esophagus; the latter was a hitherto unreported location for this tumor. The schwannomas ranged from 2 to 11 cm in diameter. They were well circumscribed but not encapsulated, with interlacing bundles of spindle cells, nuclear atypia and no mitosis, interspersed with collagenous strands. Inflammatory cells were scattered throughout the tumors and a peripheral cuff of lymphoid aggregates was observed in all cases. Intracellular periodic acid-Schiff (PAS)-positive crystalloids were found in three cases; no skeinoid fibers were seen. A diffuse and intense positivity for vimentin and S-100 protein was detected in all five cases together with a variable and sometimes focal positivity for glial fibrillary acidic protein and neuron-specific enolase. None of the tumors showed expression of CD34 or the smooth muscle antigens tested. The four cases with a sufficient follow-up had a favorable outcome without any recurrence or metastasis. The morphologic and immunohistochemical features of digestive schwannomas were compared with those of other gastrointestinal stromal tumors. Schwannomas have many differences. Digestive schwannomas can be readily recognized on histologic and immunohistochemical examination. They are spindle cell tumors without epithelioid features, with a peripheral cuff of lymphoid tissue. Specific intracellular needle-shaped PAS-positive crystalloids are found in some cases, whereas skeinoid fibers are not. These tumors always express S-100 protein in a diffuse and strong manner, and they express glial fibrillary acidic protein but not express CD34. Digestive schwannomas usually are gastric tumors and have never been reported in the small bowel. They pursue a benign course and are far rarer than gastrointestinal autonomic nerve tumors.