Tamoxifen-associated postmenopausal adenomyosis exhibits stromal fibrosis, glandular dilatation and epithelial metaplasias.

AIMS: Adenomyosis is relatively rare in postmenopausal women but recent reports have described its occurrence in this age group in patients taking tamoxifen. This study describes the pathology of nine cases of adenomyosis in postmenopausal women who were taking this medication. METHODS AND
RESULTS: The pathology of the nine tamoxifen-associated cases was compared to five cases of postmenopausal adenomyosis not associated with tamoxifen. Morphological features present within adenomyosis more often in those taking tamoxifen were cystic dilatation of glands (which sometimes resulted in grossly visible intramural cystic lesions), fibrosis of the stroma and various epithelial metaplasias. The proliferative activity within the adenomyosis, as determined by MIB1 staining, was higher in the tamoxifen group.
CONCLUSIONS: The study supports an association between tamoxifen therapy and the presence of adenomyosis in postmenopausal women. The aforementioned morphological features are characteristic of polypoid and nonpolypoid surface endometrium associated with tamoxifen and their occurrence within the adenomyosis is likely to represent extension of the surface epithelial changes. Adenomyosis may be more common than is generally realized in women taking tamoxifen and may account for postmenopausal bleeding in these patients.