Esophageal stromal tumors - A clinicopathologic, immunohistochemical, and molecular genetic study of 17 cases and comparison with esophageal leiomyomas and leiomyosarcomas

Although rare elsewhere in the gastrointestinal tract, leiomyomas (LMs) are the most common esophageal mesenchymal neoplasms. In contrast, gastrointes tinal stromal tumors (GISTs) predominate in the stomach and intestines but have not been documented in the esophagus, This study was undertaken to det ermine the clinicopathologic features and frequency of esophageal GISTs com pared with LMs and leiomyosarcomas (LMSs) of the esophagus, A total of 68 s tromal/smooth muscle tumors from the Armed Forces Institute of Pathology an d the Haartman Institute of University of Helsinki were reclassified by cur rent histologic and immunohistochemical criteria. There were 17 GISTs, 48 L Ms, and three LMSs. The esophageal GISTs occurred in 12 men and five women with a median age of 63 years (range, 49-75 years). All tumors were from th e lowest third of the esophagus, and the most common complaint was dysphagi a, whereas two tumors were detected incidentally. Histologically the tumors had an overall basophilic appearance and showed combinations of solid, myx oid, and perivascular collarlike patterns with a spindle cell histology in 13 patients and epithelioid histology in four patients. All tumors were pos itive for CD117 and for CD34, whereas two patients were also positive for a lpha-smooch muscle actin (SMA) and three patients were positive for desmin. One patient showed a unique immunophenotype with coexpression of CD117, CD 34, SMA, and desmin. Nine patients died of disease, including all who had a tumor larger than 10 cm, and also one patient whose tumor showed five mito ses per 50 high-power fields. In comparison, esophageal LMs (n = 48) occurr ed in a younger population (median age, 35 years) but, similar to the GIST group, men predominated (67%). All LMs were clinically indolent rumors with Do tumor related mortality. The LMs showed eosinophilic cytoplasm, and wer e positive for desmin and SMA, and negative for CD117 and CD34. All three L MSs were large high-grade tumors that showed muscle cell markers but no CD1 17. All patients died of disease. Esophageal GISTs showed mutations in exon 11 of c-kit as described previously in gastric and intestinal GISTs. The s eparation of GISTs from esophageal LMs is important diagnostically because the former group has a high risk of malignant behavior.