Adenomatoid tumour of the uterus is frequently associated with iatrogenic immunosuppression

AIMS: Uterine adenomatoid tumour (AT) is a benign proliferation of cells showing mesothelial differentiation within the myometrium that usually presents as a single nodule. Rare diffuse uterine ATs have been reported, often in patients undergoing immunosuppressive therapy. Herein, we aimed to elucidate the general association between the incidence of uterine AT and iatrogenic immunosuppression by cohort analysis. METHODS AND RESULTS: We analysed 611 consecutive hysterectomy specimens to determine the incidence of AT and its correlation with the immunosuppressive status. Mesothelial lineage, p16 expression, mismatch repair (MMR) protein alterations, and the possible integration of tumorigenic viruses were examined by in situ hybridizasion and immunohistochemistry. ATs were detected in 14 of 611 hysterectomy cases (2.3%). The incidence of AT was significantly higher in the immunosuppressed (IS) group (5/20, 25.0%) than in the non-IS group (9/591, 1.52%), with a relative risk of 16.4. Of the five ATs in the IS group, three were multifocal or diffuse. Latent uterine AT was detected, by in toto sectioning, in one of four immunosuppressed autopsy cases. The tumor cells of ATs commonly expressed calretinin and podoplanin. Characteristic block-type (≥90%) positivity for p16 was observed in most ATs. None of the ATs were positive for human herpes virus type 8, Merkel cell polyomavirus, SV40 large T antigen, Epstein-Barr virus, and human papilloma virus, and the MMR proteins were retained. A TRAF7 mutation was identified from macrodissected tissue in one of 12 ATs by Sanger sequencing. CONCLUSION: Uterine AT is an immunosuppression-associated mesothelial lesion characterised by p16 overexpression.