Abstract
A 78-year-old man presented with a prostate-specific antigen (PSA) level of 35 ng/mL, a PI-RADS 5 lesion on multiparametric prostate MRI, and negative whole-body bone scintigraphy. Within five months, PSA increased to 1244 ng/mL despite minimal radiological progression of the primary tumour. Repeat MRI demonstrated multiple osseous lesions, repeat MRI–ultrasound fusion-guided biopsy confirmed Grade Group 5 adenocarcinoma with cribriform architecture and perineural invasion, and repeat bone scintigraphy revealed an oncologic superscan consistent with high-volume metastatic disease. This case demonstrates that rapidly rising PSA levels accompanied by new skeletal symptoms should prompt immediate repeat staging despite initially negative whole-body bone scintigraphy.