Endocrine Abstracts (2017) 49 GP194 | DOI: 10.1530/endoabs.49.GP194

Serotonin, ATRX and DAXX as differential diagnostic markers of neuroendocrine tumours (NETs) in the sellar region. An immunohistochemical study in a large series of pituitary adenomas and in a non-pituitary NET

Olivera Casar-Borota1,2, Johan Botling1,2, Dan Granberg3, Johan Wikström4, Fredrik Pontén1,2 & Jacqueline Trouillas5,6

1Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden; 2Department of Clinical Pathology, Uppsala University Hospital, Uppsala, Sweden; 3Department of Medical Sciences, Uppsala University, Uppsala, Sweden; 4Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; 5Faculté de Médecine Lyon-Est, Université Lyon 1, Lyon, France; 6Centre de Pathologie et de Biologie Est, Groupement Hospitalier Est, Hospices Civils de Lyon, Bron, Lyon, France.

We present a case of a patient with a locally invasive, serotonin- and ACTH-reactive tumour in the sellar region, filling the sphenoid sinus and expanding into the epipharynx. Clinical examination completed by 68-Gallium-DOTA-TOC PET revealed tracer uptake in the sellar tumour as well as in a 7 mm lesion in the pancreatic tail. A differential diagnosis between silent corticotroph adenoma and another primary or secondary neuroendocrine tumour (NET) with ACTH-expression was difficult.

As serotonin was strongly positive in the tumour cells and its expression in pituitary endocrine tumours has not been systematically studied, we performed immunohistochemical analysis of serotonin in a large series of pituitary adenomas of different hormonal types from 246 patients. In addition, ATRX and DAXX, which mutations are associated with a subset of pancreatic NETs have been studied by using immunohistochemistry in the same cohort of pituitary tumours.

None of the examined pituitary tumours expressed serotonin. There was normal expression of ATRX and DAXX corresponding to a lack of ATRX/DAXX mutations in the pituitary tumours.

Thus, serotonin-immunolabelling tumours in the sellar region most probably represent primary or secondary neuroendocrine tumours of non-pituitary origin. ATRX and DAXX do not seem to be involved in the pathogenesis of pituitary adenomas. Demonstration of ATRX or DAXX mutations in a neuroendocrine tumour of the sellar region excludes pituitary adenoma and suggests a non-pituitary NET, probably of pancreatic origin.

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