Metastatic Small Cell Neuroendocrine Carcinoma of the Prostate: A Rare and Aggressive Case Report From Bangladesh.

BACKGROUND: Small cell neuroendocrine carcinoma of the prostate (SCNEC) is a rare but devastatingly aggressive malignancy, carrying a median survival well under 13 months even with multimodal treatment. It may arise de novo or emerge as a treatment-resistance phenotype following androgen deprivation in conventional prostatic adenocarcinoma. A defining and clinically treacherous feature is its failure to elevate serum PSA in proportion to tumour burden-a phenomenon termed the 'PSA paradox'-which routinely delays diagnosis, particularly in resource-limited settings. CASE PRESENTATION: We report a 35-year-old Bangladeshi man who presented with obstructive urinary symptoms, constipation and deep pelvic pain. His serum PSA was only 0.77 ng/mL despite a 6.5 × 6.0 × 5.5 cm prostate mass with liver metastases, extensive osteoblastic bone deposits (SUVmax ~18 on 18F-FDG PET/CT), left hydronephrosis and regional lymphadenopathy. Initial TRUS-guided biopsy was reported as Gleason 5 + 5 = 10 adenocarcinoma. Given the PSA-disease burden mismatch, biopsy slides were immediately re-evaluated; haematuria and acute urinary retention necessitated urgent TURP on 4 December 2024, which confirmed a pure de novo SCNEC with diffuse synaptophysin positivity and a Ki-67 index exceeding 60%. GATA3 and p40 were negative. Renal function was confirmed adequate before platinum therapy following palliative TURP(serum creatinine 1.2 mg/dL); etoposide-cisplatin (EP) chemotherapy was administered for six cycles with standard hydration, achieving a marked metabolic response on interim PET/CT. Consolidative pelvic IMRT (55 Gy/20 fractions) followed. Despite this approach, the disease relapsed within 3 months; second-line docetaxel produced no meaningful response. The patient died approximately 11 months from diagnosis. CONCLUSIONS: This case underscores the critical importance of recognising the PSA paradox in younger patients with bulky pelvic disease, the indispensable role of a comprehensive IHC panel in confirming the neuroendocrine phenotype and the urgent need for novel therapeutic strategies in this near-universally lethal malignancy.