A Rare Case of Prostate-Specific Antigen-Producing Metastatic Parotid Adenocarcinoma Developing Androgen Receptor Resistance.

A 62-year-old man presented with a rising serum concentration of prostate-specific antigen (PSA) to 53.3 ng/mL (to convert to μg/L, multiply by 1) and a PSA doubling time of 2.6 months. Computed tomography, fluorodeoxyglucose-positron emission tomography, and C-11 choline positron emission tomography demonstrated a parotid mass with innumerable lytic bone lesions and diffuse metastatic disease to the neck and mediastinal lymph nodes. Mediastinal lymph node biopsy revealed salivary ductal adenocarcinoma that produced PSA and demonstrated androgen receptor sensitivity. The patient had a prolonged clinical benefit to first- and second-line hormone therapy, and his PSA levels correlated with treatment response, development of hormone resistance, and progression. In summary, urologists, pathologists, and primary care providers should be aware that a rising PSA level in the setting of a head and neck mass in a patient without a history of prostate cancer does not constitute a diagnosis of metastatic prostate adenocarcinoma and that other primary tumors should be considered and a broader imaging and pathologic evaluation is indicated.