Vanek's tumor (inflammatory fibroid polyp). Report of 18 cases and comparison with three cases of original Vanek's series.

Eighteen cases of Vanek's tumors are presented. The patients included nine men and nine women between the ages of 45 and 93 years (mean, 66.2 years). Nine cases were clinically diagnosed as polyps of the gastric antrum, five cases as polyps of the stomach (not otherwise specified), one polyp was located in the ileum and the three remaining polyps in the small intestine (not otherwise specified). The thirteen polyps with available size information measured from 0.4 to 5 cm in the greatest diameter (mean, 2.2 cm). Immunohistochemically, the affections were positive for vimentin (18/18) and CD34 (15/18). All the cases negative for CD34 also lacked concentric onion skin-like formations of the spindle cells around glands and vessels. The different immunophenotype and absence of concentric formations could be explained by the existence of two different lesions commonly designated as Vanek's tumor (inflammatory fibroid polyp) or by the hypothesis of various evolutional stages. In the differential diagnosis, it is important to distinguish namely eosinophilic gastroenteritis, gastrointestinal stromal tumor, inflammatory pseudotumor, hemangioendothelioma, and hemangiopericytoma. In contrast to gastrointestinal stromal tumors, genetically no substitution, deletion, or insertion occurred in c-kit exon 11 in all analyzed samples. Likewise, no deletion or insertion in part of c-kit exon 9 was observed.