A Case Report on Endometriosis-Associated Intestinal Tumour Following Hysterectomy: Diagnostic Challenges and Implications for Hormone Replacement Therapy (HRT) Guidelines

Endometriosis is a complex condition that is often underdiagnosed, leaving rare but serious risks such as malignant transformation overlooked in many cases. Malignant transformation, especially in extra-gynaecological sites, poses significant diagnostic and therapeutic challenges. We present a case of an endometriosis-associated intestinal tumour diagnosed in a patient with exposure to oestrogen-only hormone replacement therapy (HRT) on a background of total abdominal hysterectomy and bilateral oophorectomy performed three decades before her presentation. This case highlights the potential for malignant transformation of residual endometriotic tissue in extra-gynaecological sites, even decades following definitive surgical management, particularly in the presence of important risk factors such as obesity and prior oestrogen-only HRT.