Primary mucinous adenocarcinoma of the endometrium. A clinicopathologic and histochemical study.

Of 256 patients with carcinoma confined to the uterine corpus at the time of hysterectomy treated in the period 1959-1975 at Stanford University Hospital, 98 patients (38%) had neoplasms which demonstrated at least focal intracytoplasmic mucin. In 21 carcinomas (9%), intracytoplasmic mucin production was the dominant form of differentiation--a group which we designate primary mucinous carcinoma of the endometrium. Freedom from relapse and frequency of myometrial invasion were not statistically different for patients whose neoplasms contained intracytoplasmic mucin, regardless of the amount of mucin present, when compared with cases of nonmucin-containing carcinoma. Using histochemical methods, it was impossible reliably to distinguish between the intracytoplasmic mucin produced by carcinomas arising in endometrium and that produced by carcinomas primary in the endocervix. Differential biopsy and fractional curettage are stressed as useful tools in making this clinically important distinction. Since both benign mucinous metaplasia and mucinous carcinoma may arise in the endometrium, it is important to establish histopathologic criteria by which the malignant lesions may be recognized. The use of criteria illustrated in this paper (which include architectural complexity of proliferation, epithelial stratification, loss of epithelial polarity, and nuclear atypicality) resulted in the recognition of mucin producing proliferations which as a group manifest a 50% incidence of myometrial invasion.