Intravascular propagation of adenomyosis within the blood vessels of the myometrium and uterine leiomyoma in a patient harboring germline mutation in the fumarate hydratase gene – a rare finding simulating malignancy

BACKGROUND: Hereditary leiomyomatosis and renal cell carcinoma is a rare genetic disorder characterized by a predisposition to the development of multiple cutaneous and uterinne leiomyomas with a potential for malignant transformation and a risk of renal carcinoma. CASE: A 39-year-old woman suffered from this disease underwent hysterectomy due to uterus myomatosus. Histologically, some tumors showed typical appearance of fumarate hydratase-deficient leiomyomas. There were foci of adenomyosis in the myometrium. As an incidental finding, multiple thin-walled blood vessels filled with conglomerates of endometrial stroma and glandular epithelium were found in the myometrium and leiomyoma. At the first look, this feature suggested an intravascular cancer propagation. However, this endometrial tissue showed bland appearance with no atypia or mitoses and revealed low proliferative activity. Even after extensive sampling of the uterus, no malignant neoplasia was revealed. The finding was reported as intravascular form of adenomyosis. CONCLUSION: A propagation of adenomyosis within the uterine blood vessels is a rare histological finding causing diagnostic difficulties as it resembles intravascular spreading of malignant neoplasm. Although this is not a tumor entity, it represents an important differential diagnosis in the oncopathological practice. The pathologist's knowledge about this phenomenon is crucial to avoid confusion with vascular dissemination of malignancy.