Proliferating multicentric reticulohistiocytosis associated with papillary serous carcinoma of the endometrium

Multicentric reticulohistiocytosis (MRH) is a rare histocytic disease characterized by destructive arthritis in association with classic skin findings. Although MRH is not strictly a paraneoplastic disease, one quarter of cases are malignancy related. We report a case of MRH with an initial remission followed by an acute exacerbation several years later heralding the clinical presentation of endometrial carcinoma. During this flareup a skin biopsy specimen revealed a diffuse dermal infiltrate composed of histiocytes with ground-glass cytoplasm and multiple atypical mitoses. Approximately 40% of the cells stained with the proliferation marker Ki-67. Treatment of endometrial carcinoma resulted in improvement of skin and joint symptoms, and a repeat biopsy specimen no longer demonstrated mitotic figures. These findings support a reactive and proliferative cause of MRH.