prostatic xanthoma: a mimic of prostatic adenocarcinoma.

Xanthoma is a localized collection of cholesterol-laden histiocytes that is usually idiopathic, but may be seen in patients with hyperlipidemia. We report seven cases of xanthoma involving the prostate, including one arising in a patient with mild hyperlipidemia. Prostatic xanthoma appeared as a solitary microscopic lesion in the peripheral zone (six cases) or transition zone (one case). One needle biopsy specimen with xanthoma was initially interpreted as well-differentiated adenocarcinoma with a clear cell (hypernephroid) pattern, but immunohistochemical studies revealed the histiocytic nature of the proliferation. Five cases (three needle biopsy specimens and two retropubic prostatectomy specimens) contained a solitary xanthoma adjacent to foci of adenocarcinoma. Another xanthoma was present in a transurethral resection specimen with nodular hyperplasia. Although unusual, xanthoma should be considered in the differential diagnosis of clear cell adenocarcinoma and other clear cell proliferations of the prostate, particularly in limited tissue samples, such as from needle biopsies and transurethral resections.