RF07 | PSAT233 The First Case Report of a de-novo Purely Prostatic Large Cell Neuroendocrine Carcinoma with Thyroid and Adrenal Metastases

BACKGROUND: Large Cell Neuroendocrine Carcinoma (LCNEC) is the rarest neuroendocrine prostatic malignancy. It usually arises after androgen-deprivation therapy (ADT), while de novo cases are even more infrequent with only 6 cases described to date. CASE PRESENTATION: A 78-year-old man with no history of ADT presented with cervical lymphadenopathy. Diagnostic approach included PET/CT, MRI, and CT scans, U/S, biopsies, cytological and immunohistochemical evaluations. CT revealed a non-enriching region on the right lobe of the thyroid gland. An 18F-FDG PET-CT found increased uptake in the thyroid gland and both adrenal glands. Neck ultrasound identified a right thyroid lobe nodule. A fine needle aspiration of the nodule was performed and cytology was consistent with poorly differentiated carcinoma. A total thyroidectomy with central and bilateral lymph node dissection was performed and the pathology report diagnosed a LCNEC metastatic to the thyroid gland. Additional metastases were identified in both adrenal glands. Despite appropriate treatment, the patient succumbed to his disease. SUMMARY: We report the first patient with a de novo purely prostatic LCNEC, metastasizing to the thyroid and the adrenal glands. CONCLUSIONS: De novo LCNECs of the prostate are very rare, highly aggressive tumors with poor prognosis. They are resistant to most therapeutic agents, have high metastatic potential and are usually diagnosed at an advanced stage. Further studies are needed to characterize these tumors. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Saturday, June 11, 2022 1:24 p.m. - 1:29 p.m.