Hyperplastic Gastric Polyposis Complicated by a High-Grade Sarcomatoid Malignancy

Abstract

1Departments of Medicine (Gastroenterology) and 2Pathology, University of British Columbia, Vancouver, British Columbia Correspondence: Dr Hugh J Freeman, University of British Columbia Hospital, 2211 Wesbrook Mall, Vancouver, British Columbia V6T 1W5. Telephone 604-822-7216, e-mail hugfree@shaw.ca Received for publication January 24, 2014. Accepted February 7, 2014 CASE PRESENTATION A 70-year-old Asian-born woman experienced intermittent melena and iron-deficiency anemia that was treated with long-term omeprazole and iron supplements. Previous studies in other hospitals in 2009 and 2010 revealed multiple hyperplastic gastric polyps in the gastric antrum and body, but no dysplasia. There was no known family history of gastric neoplasia or previous Helicobacter pylori infection. In 2012, she experienced an additional episode of melena. Gastroscopic evaluation confirmed the presence of multiple small and large gastric polyps, typical of hyperplastic polyps (1) (Figures 1A and 1B), some with focal erosions but no dysplasia, along with a superimposed large ulcerating and polypoid lesion in the gastric body consistent with a high-grade malignancy (Figures 2A and 2B). Routine immunostaining of these biopsies to exclude stromal tumours as well as tumours of smooth muscle and neural origin with CD-117, actin and S-100 were negative. Subtotal gastrectomy showed an anaplastic spindle and epithelioid neoplasm consistent with an undifferentiated high-grade sarcomatoid malignancy (sarcoma versus sarcomatoid carcinoma), but not a gastrointestinal stromal tumour (GIST), localized to the stomach without nodal or distant metastases. Extensive immunohistochemical staining for epithelial, neuroendocrine, hematopoietic and melanocyte differentiation on the resected gastric malignancy were negative. The following stains were all negative: CD117 and DOG1 for GIST; smooth muscle actin, desmin, caldesmon for leiomyosarcoma; S100, Melan A, HMB45 for malignant peripheral nerve sheath tumour, melanoma and PECOMA; CD31 and CD34 for angiosarcoma; synaptophysin, chromogranin and TTF1 for neuroendocrine differentiation; cytokeratins 7, 19, 20, Cam 5.2 and CDX-2 for epithelial differentiation; and CD45, CD20, CD3 and ALK1 for lymphoreticular origin.