DEMONSTRATION OF INSULIN PRODUCTION AND STORAGE IN INSULINOMAS BY IN-SITU HYBRIDIZATION AND IMMUNOCYTOCHEMISTRY

Twelve cases of insulinoma were studied to assess the amount of hormon e synthesis and hormone storage by the tumour and to see what effect a hormone-producing tumour has on the adjacent normal islets. This was investigated by performing in situ hybridization, which detects hormon e messenger RNA, thus giving an indication of the degree of hormone sy nthesis by the tumour, and immunocytochemistry, which detects the horm one itself, thus giving an indication of the amount of hormone stored in the tumour cells. It was found that in most cases there was less ho rmone stored within the tumour cells than in adjacent islet cells. In a minority of cases, this decrease in stored hormone was associated wi th reduced hormone synthesis, but the majority of cases showed either equivalent or increased levels of hormone mRNA in the tumour cells com pared with adjacent islets. In addition, it was noted that, unlike som e other endocrine organs, the presence of a hormone-producing tumour w ithin the pancreas did not appear to inhibit hormone synthesis in the adjacent normal tissue.