Hemangiopericytoma is a rare mesenchymal tumor arising from special cells known as "pericytes," present on the outer walls of the capillaries. This neoplasm, first described by Stout in 1942, can occur in any part of the body but the majority are confined to the trunk and lower limbs. It can affect both sexes equally and all age groups, but occurs principally in adults in the 4th decade of life. Occasionally, the spectrum of variations in its histoiogic features lead to misinterpretation; such errors can be avoided by the use of electron microscopy. Approximately 50% are malignant and certain criteria are used to differentiate the benign from its malignant counterpart.This paper is based on a study of 6 patients seen in a special referral center during a 10-year period; in 2 patients electron microscopic studies were undertaken to confirm the diagnosis. Four patients (66%) died within 5 years, and the remaining 2 are alive without recurrence at 6 years and 32 mouths, respectively. The literature on hemangiopericytoma is briefly reviewed from a surgeon's viewpoint, with special reference to the place of preoperative tumor embolization and recent advances made in the field of adjuvant radiotherapy and chemotherapy.

SUMMARY This paper describes two cases of gastric leiomyoblastoma (bizarre smooth muscle tumour), one of them having evidence of metastases. Both patients remain well after seven years and three and a half years respectively. The literature is reviewed, and the clinical features, diagnosis, and treatment are discussed. The histological appearances are described in detail and an attempt is made to assess the criteria for the diagnosis of malignancy.Smooth muscle tumours are the commonest nonepithelial tumours of the stomach, and the occurrence of both benign and malignant forms is higher in this organ than elsewhere in the gastrointestinal tract. They form 2.47% of all gastric tumours (Skandalakis, Gray, and Shepherd, 1960

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