A case of MPO- and PR3-ANCA-negative pauci-immune renal-limited small-vessel vasculitis associated with endometrial neuroendocrine small cell carcinoma.

A 69-year-old woman was admitted to our hospital for rapid increase in serum creatinine level with microscopic hematuria and nephrotic-range proteinuria. Three months prior to admission, she became aware of atypical genital bleeding, leading her gynecologist to suspect endometrial cancer. Light microscopy examination of renal biopsy revealed crescentic glomerulonephritis with peritubular capillaritis. Immunofluorescence microscopic examination did not detect any significant staining, and no electron-dense deposits were detected by electron microscopy. No autoantibodies, including anti-myeloperoxidase- or anti-proteinase3-anti-neutrophil cytoplasmic antibodies were detected. The patient underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy and was found to have endometrial neuroendocrine small cell carcinoma (NSCC), stage 1B. In her clinical course, her serum creatinine level gradually improved without immunosuppression therapy. Endometrial NSCC is a rare endometrial malignancy. This is the first case report of vasculitis associated with NSCC originating from the uterus.