Fine needle aspiration cytology of papillary endometrioid carcinoma of the prostate. The grooved nucleus as a cytologic marker.

The fine needle aspiration (FNA) cytologic findings of an endometrioid carcinoma of the prostate are presented, along with the histologic, immunohistochemical and endoscopic features. Cystoscopy of an elderly male patient with hematuria and symptoms of bladder outlet obstruction showed the delicate papillary growths at the verumontanum that are characteristic of this lesion. Transrectal FNA of the prostate produced samples that included clusters of malignant cells with crowding and overlapping of hyperchromatic nuclei containing prominent nucleoli and a loss of polarization and cohesion. Many of the groups of tumor cells suggested papillary structures. A novel finding in the aspirate was a grooved nucleus in 10% of the tumor cells. Immunohistochemical staining of biopsy sections of the papillary growths for prostate-specific antigen was strongly positive. It is important to recognize this variant of prostatic carcinoma since its behavior and response to therapy are not yet established.