Characterization of Endocrine Cells and Tumours in the Stomach

Sammanfattning: Enterochromaffin-like (ECL) and ghrelin cells, in the human gastric mucosa and in gastric endocrine tumours (GETs), were subclassified with respect to immunohistochemical reaction vs. vesicular monoamine transporter 2 (VMAT-2), ghrelin/obestatin, and histidine decarboxylase (HDC). The immunohistochemical expression of ghrelin/obestatin and HDC in GETs was related/correlated to plasma ghrelin/obestatin and urinary methyl imidazole acetic acid (U-MeImAA) excretion respectively, with the intention of identifying markers for these tumour types.ECL cells in the gastric mucosa appear either with VMAT-2 only, or with HDC immunoreactivity only, or they can express both proteins; but in GETs the transporter protein and the enzyme were almost always co-expressed in the same cells. Furthermore, ghrelin and obestatin were co-localized in the same cells in the gastric mucosa and in the tumours. In the gastric mucosa, occasional ghrelin/obestatin cells expressed VMAT-2, but in GETs these proteins were always co-localized. Ghrelin expressing cells were non-immunoreactive to HDC. Plasma ghrelin/obestatin concentrations remained low in patients with GETs, irrespective of the relative incidence of these cells in the mucosa and in tumours. The plasma values were not related/correlated to various clinico-pathological parameters. A malignant ghrelinoma was however an exception. The tumour released high total and active ghrelin concentrations into the blood circulation. The patient suffered from diarrhoea, hypothyroidism and diabetes mellitus, but it is not clear if these conditions were due to hyperghrelinaemia. The excretion U-MeImAA was increased in a few patients with GETs, but this increase was not always related to clinical symptoms.In conclusion, ECL cells are an heterogeneous group according to VMAT-2 and HDC immunoreactivity. Ghrelin and obestatin are expressed in the same cells in the gastric mucosa, and a few of these cells display VMAT-2 immunoreactivity. Ghrelinoma is a new gastric tumour entity.