Castration-Resistant Prostate Cancer Presenting as Bulky Lymphadenopathy: A Case without Bone Metastasis.

BACKGROUND Prostate cancer (PCa) tends to spread most often to the regional lymph nodes and then to the skeleton. The prevalence of bone metastases is more than 80% in patients with metastatic PCa. Non-regional lymph node (NRLN) metastasis is defined as cancer cells spreading to lymph nodes distant from the primary tumor and often signals a more advanced stage of cancer. We are reporting such a rare case of NRLN without skeletal metastasis in PCa. CASE REPORT We report a rare case of persistently elevated PSA >20 ng/mL after the treatment of localized PCa in the past. A workup by PSA positron emission tomography (PSMA-PET) scan showed the presence of bulky retroperitoneal massive lymphadenopathy, a type of NRLN metastasis, in the absence of bone metastasis. The patient was then treated with abiraterone plus docetaxel, leading to a decrease in PSA levels from 21 ng/mL to 2.42 ng/mL. The PSMA-PET scan also showed significant shrinkage of lymphadenopathy, marking a favorable response. CONCLUSIONS Castration-resistant PCa typically metastasizes to bone, but our case presents a rare occurrence of bulky NRLN metastasis without skeletal involvement. The use of PSMA-PET imaging and genetic testing can help identify this atypical metastatic pattern. Early recognition is crucial, as it enables more accurate diagnosis and prompt treatment decisions and improves outcomes through timely intervention and personalized therapeutic strategies.