Lanreotide therapy in a case of thymic neuroendocrine carcinoma associated with syndrome of inappropriate antidiuretic hormone secretion

Neuroendocrine tumours of the thy mus are rare neoplasms, which account for 2-4% of all anterior mediastinal tu mours. Several endocrinopathies were found to be associated with these tu mours, with ectopic ACTH secretion re ported most frequently. Here we provide a description of the syndrome of inap propriate antidiuretic hormone secretion (SIADH) accompanying neuroendocrine thymic carcinoma. A mediastinal tumour was incidentally found on routine chest X-ray examina tion in a 55-year-old man. After detailed imaging studies, tumour excision was performed. The mediastinal tumour (11 ◊ 8 ◊ 4 cm) presented features of in vasion to the left lung and pericardium. Histopathological examination con firmed the diagnosis of thymic neu roendocrine carcinoma. The patient was treated with chemotherapy because of the recurrence. Symptoms of carcinoid syndrome and positive result of the so matostatin receptor scintigraphy justi fied subsequent introduction of so matostatin analogue therapy. At this point low serum sodium levels accom panied by decreased serum osmolarity and inadequate urine concentration were found. Having excluded other typ ical causes, SIADH syndrome due to ec topic vasopressin synthesis was as sumed. This finding adds to differential diagnosis of hyponatraemia, indicating that SIADH may also accompany thymic neuroendocrine tumours.