Splenic lesion mimicking breast metastasis: The first description of splenic parenchymal endometriosis

Introduction: Splenic parenchymal endometriosis has never been described to date. We report here the case of real parenchymal endometriosis of the spleen. Case description: In this case, a 54-year-old female patient presented a histologically proven metastatic recurrence of breast cancer in the internal breast chain. The CT-scan also detected a large cystic structure developed from the spleen, but non-suspected to be metastasis. The patient was treated with chemotherapy (paclitaxel) and a combination of targeted therapies (everolimus and trastuzumab). While a complete radiological and biological response was noted at 2 months, the splenic cyst gradually decreased over the years. When targeted therapies were stopped, a reincrease of the splenic lesion and de novo significant hypermetabolism of the splenic parenchyma on 18F-FDG PET scan were observed. A splenectomy was finally performed and revealed splenic parenchymal endometriosis. Conclusion: This case once again highlights the complexity of endometriosis disease, from a pathophysiological point of view, but also the difficulties of radiological characterisation, and diagnostic management.