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Presented by George Netto, M.D. and prepared by Zarir E. Karanjawala, M.D., Ph.D.
Case 2: A 40 year old woman was found to have a 2.0 cm well circumscribed gastric mass on imaging studies.
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Question 1 of 1
1. Question
Week 310: Case 2
A 40 year old woman was found to have a 2.0 cm well circumscribed gastric mass on imaging studies. A partial gastrectomy was performed.images/netto0507072a.jpg
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images/netto0507072e.jpgCorrect
Answer: Schwannoma
Histology: Digestive tract schwannomas are rare, benign, well circumscribed, mesenchymal tumours usually affecting females between 30 and 60 years old. They are often asymptomatic and most commonly occur in the stomach. Their size ranges from 2 to 11 cm in diameter. GI tract schwannomas are composed of interlacing bundles of spindle cells containing tapered to wavy nuclei. Occasional “degenerative” nuclear atypia is seen without increased mitotic activity. Interspersed collagen strands, a storiform pattern and vague nuclear palisading can also be present. Like our current example, most lesions show a characteristic lymphoid cuff often containing germinal centers.
Discussion: Immunohistochemically, diffuse and intense positivity for vimentin and S-100 protein is expected with focal reactivity to glial fibrillary acidic protein. A negative reaction with smooth muscle markers, c-KIT, CD34, neurofilament proteins and HMB45 helps eliminate other spindle cell lesions that may enter the differential diagnosis. Almost half of conventional non-GI tract schwannomas, whether sporadic or arising in the setting of familial neurofibromatosis 2 (NF2), show loss of heterozygosity (LOH) at the NF2 gene on chromosome 22q with or without an associated inactivating NF2 mutation. In the largest study on schwannomas of the GI tract by Lasota et al., only one of 20 analyzed tumors revealed evidence of LOH of the NF2 gene. The findings support the hypothesis that GI schwannomas may represent a morphologically and genetically distinct group of peripheral nerve sheath tumors.
Reference(s):
– Khan AA, Schizas AM, Cresswell AB, Khan MK, Khawaja HT. Digestive tract schwannoma. Dig Surg. 2006;23(4):265-9.
– Lasota J, Wasag B, Dansonka-Mieszkowska A, Karcz D, Millward CL, Rys J, Stachura J, Sobin LH, Miettinen M. Evaluation of NF2 and NF1 tumor suppressor genes in distinctive gastrointestinal nerve sheath tumors traditionally diagnosed as benign schwannomas: s study of 20 cases. Lab Invest. 2003 (9):1361-71.
– Prevot S, Bienvenu L, Vaillant JC, de Saint-Maur PP. Benign schwannoma of the digestive tract: a clinicopathologic and immunohistochemical study of five cases, including a case of esophageal tumor. Am J Surg Pathol. 1999 (4):431-6.Incorrect
Answer: Schwannoma
Histology: Digestive tract schwannomas are rare, benign, well circumscribed, mesenchymal tumours usually affecting females between 30 and 60 years old. They are often asymptomatic and most commonly occur in the stomach. Their size ranges from 2 to 11 cm in diameter. GI tract schwannomas are composed of interlacing bundles of spindle cells containing tapered to wavy nuclei. Occasional “degenerative” nuclear atypia is seen without increased mitotic activity. Interspersed collagen strands, a storiform pattern and vague nuclear palisading can also be present. Like our current example, most lesions show a characteristic lymphoid cuff often containing germinal centers.
Discussion: Immunohistochemically, diffuse and intense positivity for vimentin and S-100 protein is expected with focal reactivity to glial fibrillary acidic protein. A negative reaction with smooth muscle markers, c-KIT, CD34, neurofilament proteins and HMB45 helps eliminate other spindle cell lesions that may enter the differential diagnosis. Almost half of conventional non-GI tract schwannomas, whether sporadic or arising in the setting of familial neurofibromatosis 2 (NF2), show loss of heterozygosity (LOH) at the NF2 gene on chromosome 22q with or without an associated inactivating NF2 mutation. In the largest study on schwannomas of the GI tract by Lasota et al., only one of 20 analyzed tumors revealed evidence of LOH of the NF2 gene. The findings support the hypothesis that GI schwannomas may represent a morphologically and genetically distinct group of peripheral nerve sheath tumors.
Reference(s):
– Khan AA, Schizas AM, Cresswell AB, Khan MK, Khawaja HT. Digestive tract schwannoma. Dig Surg. 2006;23(4):265-9.
– Lasota J, Wasag B, Dansonka-Mieszkowska A, Karcz D, Millward CL, Rys J, Stachura J, Sobin LH, Miettinen M. Evaluation of NF2 and NF1 tumor suppressor genes in distinctive gastrointestinal nerve sheath tumors traditionally diagnosed as benign schwannomas: s study of 20 cases. Lab Invest. 2003 (9):1361-71.
– Prevot S, Bienvenu L, Vaillant JC, de Saint-Maur PP. Benign schwannoma of the digestive tract: a clinicopathologic and immunohistochemical study of five cases, including a case of esophageal tumor. Am J Surg Pathol. 1999 (4):431-6.
