POMC and large cell neuroendocrine carcinoma: A case of IAD complicated by LCNEC further supported this mechanism: cancerous tissues showed ectopic proopiomelanocortin (POMC) expression and lymphocytic infiltration, and circulating autoantibodies against POMC were detected, confirming IAD as a paraneoplastic syndrome in this patient.[12] POMC conversion to ACTH requires prohormone convertases and mature secretory vesicles.