Introduction

Uterine leiomyomas are the most common neoplasm of the uterus in women. Massive lymphocytic infiltration in a myoma is an unusual finding. It is characterised by the varying intensity of lymphocyte infiltration, the presence of scattered plasma cells, eosinophilia, and rarely, other items. We would like to call attention to such a rare lesion.

Case description

We present the case of a 31-year-old woman who had undergone surgical excision of a uterine tumour. Grossly, it had the typical uterine smooth muscle wall consistency. The microscopic examination revealed leiomyoma with heavy infiltration composed mainly of lymphocytes. On immunohistochemistry, in the lymphocytic infiltrate the T mature (CD3+/CD5+/TdT–) lymphocytes, small and of cytotoxic (CD8+/CD56–) type, prevailed, with moderate proliferative activity (expression of Ki67 found in ca. 30-40% of the cells), whereas B lymphocytes (CD20+/CD5–/TdT–) were innumerous and present in nodular aggregates. Despite a strong suspicion of neoplastic lymphoproliferation, the histopathological diagnosis was: leiomyoma with massive lymphoid infiltration. The cause of this feature is not known, although the gonadotropin-releasing hormone agonist and post-menopausal processes may promote such transformations. In differential diagnosis, malignant lymphoma, inflammatory pseudotumour, and pyomyoma should be included.

Conclusions

Lymphocytic infiltration within the uterine myoma is rare. The recognition of its distinct histological features is important to avoid possible misdiagnosis.