Pelvic MRI, FDG-PET/CT, and Somatostatin Receptor Scintigraphy Findings of Treatment-Related Neuroendocrine-Differentiated Prostate Cancer

Treatment-related neuroendocrine-differentiated prostate cancer (NEPC) is a rare tumor entity that transdifferentiates from adenocarcinoma as an adaptive response to androgen receptor pathway inhibition. We report a 79-year-old male with treatment-related NEPC, presenting as rectal bleeding after hormonal therapy. MRI showed a 51 × 52 × 65 mm tumor occupying almost the whole prostate gland and invading the seminal vesicle and rectum as moderately heterogeneous hypointensity on T2-weighted image, restricted diffusion on apparent diffusion coefficient map and diffusion-weighted imaging, and heterogeneous enhancement on Gd-enhanced T1-weighted image. FDG-PET/CT showed strong FDG uptake of the prostate tumor, and somatostatin receptor scintigraphy (SRS) showed mild uptake of the prostate tumor. The surgically resected specimen revealed NEPC. If prostate cancer worsens despite conventional therapy, treatment-related NEPC should be considered, and the benefit of imaging examinations including prostate MRI, FDG-PET/CT, and SRS is in localizing lesions with neuroendocrine differentiation.