ACTH-secreting metastatic prostate cancer with neuroendocrine differentiation

Cushing's syndrome (CS) due to ectopic adrenocorticotropic hormone (ACTH) secretion (EAS) can result from a variety of tumours and rarely from those of prostatic origin. We present a male patient in his early 60s with ACTH-secreting metastatic prostate adenocarcinoma with neuroendocrine differentiation (ICD-O code 8574/3) years after prostatectomy and androgen-deprivation therapy, initially presenting with Cushingoid features. After open radical prostatectomy and bilateral orchiectomy for disease recurrence, the patient was found to have metastatic liver and bone lesions highly suggestive of metastatic prostatic cancer. About 10% of cells on liver biopsy expressed ACTH, a finding consistent with EAS as the cause of CS. His stay was complicated with multiple infections and ultimate death. Hence, we report a case of metastatic prostate adenocarcinoma with neuroendocrine differentiation who presented with CS. We also emphasize the importance of adequate and timely treatment.