Israel Medical Association Journal

Background: The diagnosis of gastrointestinal stromal tumors is based on documentation of c-KIT and platelet-derived growth factor-alpha receptors or specific c-KIT mutations. Before the diagnosis of GIST[1] was possible, all cases had been classified as sarcomas or benign tumors.

Objectives: To identify cases of GIST formerly diagnosed as abdominal or retroperitoneal mesenchymal tumors.

Methods: We reviewed the archive material on all surgical cases diagnosed as gastrointestinal related malignant mesenchymal tumors or GIST in our medical center during the last decade (1995–2004).

Results: Sixty-eight cases of retroperitoneal soft tissue sarcoma were identified. Thirty-eight were reconfirmed to be GIST, 19 were newly diagnosed as GIST (the hidden cases), 8 cases were re-diagnosed as mesenchymal tumors, and 3 cases of sarcoma remained sarcomas. Of all the GIST tumors, c-KIT-positive and PDGFRα[2]-positive tumors were more characteristic of primary gastric tumors, while c-KIT-positive and PDGFRα-negative tumors were found in the colorectal area. The c-KIT-negative and PDGFRα-positive cases were of gastric origin.

Conclusions: Any c-KIT-negative malignant mesenchymal mass located near the proximal gastrointestinal tract should also be stained for PDGFRα to differentiate between GIST and other soft tissue sarcomas. Practically, formerly diagnosed abdominal or retroperitoneal soft tissue sarcomas should be reviewed to identify patients with misdiagnosed GIST and thereby avoid future unnecessary and ineffective chemotherapy.

A 32 year old man presented with a huge tumor in the right chest wall that had increased dramatically in size over the previous 6 months.

Background: Classic Kaposi's sarcoma is a rare tumor with an indolent behavior. Local therapy is not applicable in disseminated cutaneous disease. Patients with advanced disease are usually treated with systemic chemotherapy.

Objectives: To assess the effectiveness and toxicity of  single-agent vinblastine in the treatment of disseminated and recurrent Kaposi's sarcoma.

Methods: Ten patients with wide cutaneous spread of classic Kaposis sarcoma were treated with single-agent vinblastine, 6 mg/m² intravenously once every 2 weeks. Vinblastine was continued for 2 months after achieving a maximal response.

Results: The male:female ratio was 2.3:1, and median age 64 years (range 50-79 years). The median number of involved nodules in the skin was 34. The overall response rate was 90%, 5 with complete response (50%) and 4 with partial response (40%). Complete responders had a longer duration of response than partial responders: 41.2 vs. 14.8 months. The median survival of all patients was 33 months. Side effects were minimal and tolerable.

Conclusions: Vinblastine is very effective in the treatment of extensive classic Kaposi's sarcoma, and results in a high response rate, long survival and disease-free survival with tolerable toxicity.