Concomitant recurrent follicular lymphoma and prostate adenocarcinoma detected during routine urologic follow-up: a rare case report.

Introduction and importance: Prostate adenocarcinoma is the most common solid malignancy in men, while follicular lymphoma is the second most frequent subtype of non-Hodgkin lymphoma. Prostatic involvement by lymphoma is rare, and synchronous occurrence of both malignancies in the prostate is exceedingly uncommon. Case presentation: A 64-year-old man with a history of follicular lymphoma in remission presented for routine prostate screening. Despite a low prostate-specific antigen (PSA; 1.03 ng/mL), digital rectal exam and magnetic resonance imaging revealed suspicious lesions. Biopsy confirmed Gleason 3 + 4 = 7 adenocarcinoma in the right peripheral zone and recurrent Grade 3a follicular lymphoma in the left. PET imaging confirmed Stage IV lymphoma. The patient began active surveillance for prostate cancer and systemic treatment planning for relapsed lymphoma. Clinical discussion: This case highlights the diagnostic complexity of dual malignancies in the prostate. Prostate adenocarcinoma typically presents with PSA elevation or abnormal digital rectal findings, but PSA may be normal in clinically significant disease. Follicular lymphoma of the prostate is often asymptomatic and underrecognized, especially when PSA is not markedly elevated. Histological examination with immunohistochemistry is essential to distinguish between inflammatory infiltrates, adenocarcinoma, and lymphoma. Literature review shows few reported cases of concurrent prostate adenocarcinoma and follicular lymphoma and none involving recurrent systemic disease. Conclusion: Clinicians should maintain a broad differential when evaluating prostate lesions, especially in patients with a history of lymphoma. Early identification of coexisting malignancies ensures tailored, multidisciplinary management.