Which of the following statement(s) regarding gastric leiomyosarcoma is/are correct?

b. The primary histological indicator of aggressive behavior is the number of mitoses per microscopic field

d. Lymphadectomy is not indicated during resection because metastases are usually hematogenous

Leiomyosarcomas occur with equal frequency in both sexes in the sixth and seventh decades of life. The tumor frequently may have prominent extraluminal growth and attain large size before causing symptoms. Leiomyosarcomas must be differentiated from their benign counterparts, leiomyomas. Grossly, the tumors are firm, gray-white masses; a pseudocapsule separating tumor from normal smooth muscle may occasionally be present. When the tumors reach a large size, central necrosis is common. Leiomyosarcomas are usually graded histologically, with the frequency of mitotic figures the prime indicator of aggressive behavior. Lesions with more than 5 to 10 mitoses per 10 high-power fields demonstrate increased metastasis.

Intraperitoneal sarcomatosis is frequent, as is local recurrence after resection. Metastasis occurs by way of the hematogenous route, and thus hepatic involvement is common. Lymphatic metastasis is observed in less than 10% of patients. Negative surgical margins must be ensured histologically, but lymphadenectomy is not indicated because of the low frequency of lymphatic metastasis. Leiomyosarcomas are not radiosensitive, and chemotherapy has not been shown to improve survival.