Tumor-like intravascular proliferations of the stroma in adenomyosis.

: Two hundred cases of adenomyosis have been studied in order to clarify the origin and significance of intravascular endometrial tissue in adenomyosis. A tumor-like intravascular proliferation of the adenomyotic stroma (IVSP) has been found in 17.5% of the cases. An endolymphatic proliferation (35 cases) was occasionally accompanied by an intravenous proliferation (3 cases). IVSP originated from a perivascular stromal proliferation (PVSP) and occurred only in deep adenomyosis. IVSP was focal and showed no atypia. It was significantly most frequent in patients 50-53 years of age and more frequent in patients up to 53 years than in those over 53. The frequency of occurrence of PVSP and IVSP was related to the histologic features of adenomyosis and the endometrium and was highest in hyperplastic adenomyosis and in adenomyosis accompanied by hyperplasia of the endometrium. The study suggests that PVSP and IVSP develop in the areas of adenomyotic stroma stimulated by estrogen and nonresponsive to progesterone. The differential diagnosis of tumor-like and sarcomatous IVSP, and histogenesis of adenomyosis are discussed.