Ectopic Cushing's syndrome secondary to lung and mediastinal tumours -- report from a tertiary care centre in Iran.

INTRODUCTION: Ectopic Cushing`s syndrome (ECS) secondary to neuroendocrine tumours (NETs) of the lung and mediastinum are rarely encountered. In this study, we present our experience in Iran on 15 patients with ECS secondary to lung and mediastinal tumours over a period of 27 years. MATERIAL AND METHODS: Since 1985, 15 patients with ECS secondary to lung and mediastinal tumours have been diagnosed and prospectively followed by the endocrinology team of Taleghani Hospital, Tehran, Iran. The clinical signs and symptoms, laboratory findings, radiological features, immunohistochemical characteristics, management strategies and outcome data are here presented. RESULTS: There were six women and nine men, aged 26-70 years, all presenting with typical features of Cushing's syndrome. Based on histopathologic evaluations, four patients had small cell lung cancer (SCLC) and seven patients had pulmonary NETs, one patient had a thymic NET, and one case was diagnosed as a lung tumourlet. The mean ± SD serum cortisol, 24h urine free cortisol and plasma ACTH were 47.2 ± 20.5 µg/dL, 2,702 ± 5,439 µg/day, and 220 ± 147 pg/mL, respectively. Pulmonary lesions ranged in diameter from 1.1 to 4 cm (mean 1.9 ± 1.1 cm). One patient had a 10 cm mediastinal mass. The duration of follow up in these cases was between one month and seven years (mean 29.9 ± 27.5 months). The four patients with SCLC died within three months of diagnosis. CONCLUSION: Our data demonstrates the protean clinical and laboratory manifestations of ECS secondary to lung and mediastinal tumours, the problems encountered in diagnosis, and the need for a multidisciplinary approach. This study confirms other series from Western Europe and North America that, unlike the SCLC patients who show a poor outlook, ECS secondary to lung carcinoids has a more favourable prognosis.