Ectopic ACTH-producing large cell neuroendocrine Pancoast tumour presenting as Horner syndrome

We present an interesting case where a patient is presented with a droopy left eyelid (as part of Horner syndrome) and Cushingoid features which were a result of a Pancoast tumour (apical lung tumour in superior pulmonary sulcus) involving the left lung. This tumour was secreting ectopic adrenocorticotropic hormone (ACTH), a paraneoplastic endocrine phenomenon, which resulted in Cushing syndrome symptomatology. Though most ectopic ACTH-producing lung cancers are either small cell or carcinoid tumours, this was in fact a large cell neuroendocrine cancer (LCNEC). Patient underwent surgical resection and adjuvant/neoadjuvant chemotherapy with radiation; however, he succumbed to LCNEC given aggressive nature of the disease.