Prostate Cystadenocarcinoma: A Rare Cystic Epithelial Lesion in an Unusual Clinical Setting

Abstract Introduction Cystic tumors of prostate are rare and their clinicopathologic significance remains to be defined. The tumors present with either obstructive urinary symptoms or elevated serum prostate-specific antigen (PSA). Here we report a multilocular cystadenocarcinoma in a patient without significant urologic symptoms. Case Report A 71-year-old male with prior abnormal prostate biopsy, 6 years previously (unknown pathology), was referred for prekidney transplant workup. His symptom of oliguria and proteinuria was associated with end-stage renal disease without any obstructive urinary symptoms. Serum PSA detected 5.5 ng/mL. Magnetic resonance imaging (MRI) of the pelvis demonstrated a multilocular cystic lesion measuring 6.2 × 4.6 cm, arising from the right peripheral zone of prostate. The patient underwent MRI-guided prostate needle biopsy. Histology of prostate biopsy revealed glands and cystic structures lined by cuboidal to columnar epithelial cells with basally located hyperchromatic nuclei, pseudostratification, and focal papillary architecture. The cyst wall was immunoreactive for Cam 5.2, NKX 3.1, and AMACR, while negative for PAX8 and 34BE12 and p63, suggesting a diagnosis of primary prostate cystadenocarcinoma. The patient underwent robotic prostatectomy. The resected specimen showed a soft periprostatic mass, 6.8 × 5.0 cm at the right posterolateral aspect. Cut sections showed multiple multilocular cysts, with papillary projections, involving the right posterior-lateral surfaces with extensive extraprostatic extension. Histology showed multilocular cysts with papillary lining. Immunohistochemical studies showed strong reactivity of the cyst lining for NKX3.1, AMACR, weak CDX-2, and absent 34be12, p63, and ERG reactivity. The microscopic and immunohistochemical evidence supported a diagnosis of prostate cystadenocarcinoma, stage pT3a with free resection margin. Conclusion Cystadenocarcinoma is a variant of prostate carcinoma associated with obstructive urinary symptoms and potential for locally advanced growth. This case and other published reports of prostate cystadenocarcinoma show histologic features similar to the ductal variant of prostate adenocarcinoma, and therefore we suggest to grade it as Gleason pattern 4. The current case of prostate cystadenocarcinoma was an incidental diagnosis in an asymptomatic patient with mildly elevated PSA (T1c).