Final Diagnosis:
Metastatic treatment-related neuroendocrine prostatic adenocarcinoma
Discussion:
Treatment-related neuroendocrine prostatic carcinoma (t-NEPC) is a rare (<1% of cases) aggressive variant of prostate cancer that emerges as a consequence of androgen deprivation therapy (ADT), most often with modern AR pathway inhibitors such as enzalutamide or abiraterone. T-NEPC mostly commonly occurs in higher-grade prostate adenocarcinomas. T-NEPC occurs in less than 24 months of ADT in over half of patients. Unlike conventional mechanisms of resistance (e.g., AR amplification or mutation), t-NEPC reflects lineage plasticity: adenocarcinoma cells transdifferentiate into an AR-independent state, typically with small-cell morphology and expression of neural/neuroendocrine markers. This transition renders the tumor resistant to AR-directed therapies and is associated with rapid progression and poor outcomes. Median survival after transdifferentiation is abysmal at approximately 7 months. Pure small-cell histology portends a worse prognosis than mixed adenocarcinoma–neuroendocrine tumors. In addition to neuroendocrine differentiation, androgen deprivation therapy can also cause prominent squamous differentiation.
Pathogenesis is tightly linked to genomic losses (TP53, RB1, PTEN) and epigenetic reprogramming. Experimental model have demonstrated that neuroendocrine tumor cells can arise directly from luminal adenocarcinoma, highlighting plasticity rather than a distinct precursor population.
Essential diagnostic criteria of t-NEPC include: (1) prostatic carcinoma with neuroendocrine morphology, (2) immunohistochemical confirmation of NE differentiation, and (3) history of prior AR-directed therapy. Histologically, t-NEPC can be pure small-cell carcinoma or mixed with high-grade adenocarcinoma, often with abrupt transitions between components. Immunophenotypically, small-cell areas generally lose PSA and PAP expression, but may retain AR in a subset, and express neuroendocrine markers synaptophysin, chromogranin, and INSM1 in a majority of cases. In transitional zones between adenocarcinoma and neuroendocrine morphologies, cells expressing both prostatic and neuroendocrine markers can be identified. TTF-1 is positive in approximately half of cases and is an important pitfall to be aware of to avoid misdiagnosing pulmonary metastases. Routine NE marker testing in all prostate biopsies is not recommended, as untreated prostatic adenocarcinomas and even non-neoplastic prostate, can contain small numbers of interspersed neuroendocrine cells. While present in less than half of cases, TMPRSS2:ERG fusions are highly specific for prostate adenocarcinoma and support prostatic origin in metastatic locations.
Overall, t-NEPC represents a distinct clinicopathologic entity with major therapeutic implications. Recognition is critical, as patients are typically shifted from AR-targeted strategies to platinum-based chemotherapy regimens, though outcomes remain poor.
References:
Akamatsu S, Inoue T, Ogawa O, Gleave ME. Clinical and molecular features of treatment-related neuroendocrine prostate cancer. Int J Urol. 2018 Apr;25(4):345-351. doi: 10.1111/iju.13526. Epub 2018 Feb 3. PMID: 29396873.
Gopalan A. Treatment-related Neuroendocrine Prostate Carcinoma-Diagnostic and Molecular Correlates. Adv Anat Pathol. 2024 Mar 1;31(2):70-79. doi: 10.1097/PAP.0000000000000431. Epub 2024 Jan 15. PMID: 38223983.
de Kouchkovsky I, Chan E, Schloss C, Poehlein C, Aggarwal R. Diagnosis and management of neuroendocrine prostate cancer. Prostate. 2024 Apr;84(5):426-440. doi: 10.1002/pros.24664. Epub 2024 Jan 3. PMID: 38173302.
Netto GJ, Amin MB, Berney DM, Compérat EM, Gill AJ, Hartmann A, Menon S, Raspollini MR, Rubin MA, Srigley JR, Hoon Tan P, Tickoo SK, Tsuzuki T, Turajlic S, Cree I, Moch H. The 2022 World Health Organization Classification of Tumors of the Urinary System and Male Genital Organs-Part B: Prostate and Urinary Tract Tumors. Eur Urol. 2022 Nov;82(5):469-482. doi: 10.1016/j.eururo.2022.07.002. Epub 2022 Aug 11. PMID: 35965208.
Yamada Y, Beltran H. Clinical and Biological Features of Neuroendocrine Prostate Cancer. Curr Oncol Rep. 2021 Jan 12;23(2):15. doi: 10.1007/s11912-020-01003-9. PMID: 33433737; PMCID: PMC7990389.