Primary prostatic mucosa-associated lymphoid tissue lymphoma: a case report and literature review

We report a rare case of early-stage primary extranodal marginal zone B-cell lymphoma of the prostate, also known as mucosa-associated lymphoid tissue (MALT) lymphoma. The patient was a 65-year-old male without obvious lower urinary tract obstruction symptoms, presenting with mild elevation of serum total prostate-specific antigen (tPSA). Digital rectal examination showed mild prostatic enlargement. Prostate biopsy, immunohistochemistry and gene rearrangement analysis were highly suggestive of MALT lymphoma. Bone marrow aspiration revealed no bone marrow involvement, and PET-CT showed no lesions in other sites. The patient was finally diagnosed with primary prostatic MALT lymphoma, Ann Arbor stage IE. He received external beam radiation therapy to the prostate, with a total dose of 26.0 Gy delivered in 13 fractions (2.0 Gy per fraction). No obvious adverse events occurred during radiotherapy, and his tPSA level returned to normal after treatment. Serial follow-up contrast-enhanced prostate magnetic resonance imaging (MRI) demonstrated a sustained radiological response after radiotherapy. At 1 month after treatment, the previously observed diffusion-weighted imaging (DWI) hyperintensity in the lesion area was no longer apparent, suggesting a favorable early treatment response. Follow-up MRI examinations at 19 and 26 months after radiotherapy showed only globally heterogeneous signal intensity of the prostate without newly developed diffusion-restricted lesions, indicating durable disease control without obvious radiological evidence of recurrence. This report aims to share our experience in managing this rare case and provide a reference for clinical practice.