Histopathologic classification of uterine choriocarcinoma

Histopathologic features of uterine choriocarcinoma were studied to establish new criteria for grading malignancy of the disease. Thirteen items of histopathologic findings concerning the degree of differentiation and the forms of masses of trophoblasts (Trs), the manner of Tr invasion, and host response of surrounding tissues were studied with relationship to prognosis in 70 patients with uterine lesions (alive, 49; dead, 21). Chi-square test results were examined for each item in relation to prognosis of the patients. Four items were thought to have significance and were selected as criteria: (1) island formation; (2) massive proliferation of intermediate-type Trs; (3) rectangular infiltration of Trs to surrounding muscle fibers; and (4) atypia of Trs at the end-point of tumor invasion. A discriminant analysis was carried out (under the standardization of tumor extension and the historical staging of treatment). From the results obtained in discriminant analysis, scores were given to the four items that existed in the specimen. New criteria for grading malignancy are proposed based on scoring these four items. The algebraic sum of the scores had a possible range of +4 to -16. Patients with scores of -9 and above had a low-grade malignancy with a mortality rate of 7%. Patients with scores of -10 and lower had a mortality of 69% and were classified as having tumors of high-grade malignancy.