Clinicopathologic study of 275 cases of gastrointestinal stromal tumors: the experience at 3 large medical centers in Mexico.

It is important to distinguish gastrointestinal (GI) stromal tumors (GISTs) from other GI mesenchymal tumors (GIMTs) because of the availability of molecular-targeted therapy for GISTs. The aim of the study was to reclassify GIMTs and to determine the clinicopathologic features of GISTs in Mexico. Cases of GIMT identified from the database of 3 large diagnostic centers in Mexico between 1995 and 2004 were reclassified according to current criteria. Hematoxylin and eosin-stained sections and clinical histories were reviewed, and immunohistochemistry was performed using anti-CD117, CD34, smooth muscle actin, and S-100 protein. A total of 275 GISTs were identified. The tumors were located in the stomach (40%), small intestine (35%), colorectum (12%), abdominal cavity (11%), and esophagus (2%). There were equal numbers of men and women with a mean age at diagnosis of 61 years. The tumors ranged in size from 3.5 to 34 cm (mean, 9.1 cm); 95 tumors (34%) were larger than 10 cm. Colorectal and omental tumors were the largest. The cell types included pure spindle (68%), pure epithelioid (16%), and mixed epithelioid/spindle (14%). Whereas 17.8% of tumors were regarded as low risk, 43% of tumors were in the high-risk category. CD117 positivity was detected in most of the tumors (96%). In addition to CD117, 255 cases (92%) were positive for CD34, 82 cases (32%) were positive for smooth muscle actin, and 13 cases (4.7%) were positive for desmin. Gastrointestinal stromal tumors in Mexico have the same clinicopathologic and immunohistochemical features as those reported in other countries. It is not always easy to distinguish GISTs from other soft tissue lesions. The diagnosis can be difficult even for experienced pathologists.

Micropapillary carcinoma of the urothelial tract. A clinicopathologic study of 38 cases.

Micropapillary carcinoma (MPC) of the bladder is a rare and aggressive variant of bladder carcinoma. The goals of this study are to investigate whether this variant of bladder carcinoma represents a more aggressive disease than conventional urothelial carcinoma (CUC) and to determine the incidence of MPC in our country. A total of 630 urothelial carcinomas diagnosed from 1997 to 2003 at the Department of Pathology, Oncology Hospital, in Mexico City were analyzed to identify MPC. Thirty-eight patients were found to have this diagnosis and along with a group of 76 patients diagnosed with CUC serve as the basis for this study. In 37 patients with MPC, the lesions were located in the bladder, and in 1 patient in the ureter. The mean patients' age at diagnosis was 68 years, and the male-female ratio was 37:1. The initial stage at presentation was high in most of the patients: Three patients had stage T1, 8 had stage T2, 18 had stage T3, and 9 had stage T4. The disease-specific survival rate for patients with MPC at 3.1 years was 39.5% (95% confidence interval [CI], 2.7%-3.4%) whereas for patient with CUC was 55.3% (95% CI, 3.9%-4.4%). Patients with a micropapillary component of more than 50% had a relative mortality risk of 2.4 (1.3-4.2), whereas patients with less than 50% of MPC did not have a significantly increased mortality risk (RR, 1.8; 0.5-6.0). In summary, in this study, MPC was far more aggressive clinically than CUC. In Mexico, the incidence of 6% of MPC in relation to CUC and the male-female ratio of 37.1 for MPC are much higher than reported in the literature.