Peanut lectin: a histochemical marker for phaeochromocytomas.

Fifty-five neuroendocrine tumours and 6 adrenocortical tumours were examined immunohistochemically for the expression of neuron-specific enolase (NSE), chromogranin and synaptophysin. The results were compared with the staining patterns obtained with peanut lectin (PNA) using a streptavidin-biotin staining technique. In separate experiments, sections were preincubated with neuraminidase for the demonstration of masked PNA binding sites. Two of the 24 phaeochromocytomas, 1 of the 6 medullary carcinomas of the thyroid gland, 5 out of the 7 islet cell tumours of the pancreas and all 4 extra-adrenal paragangliomas were negative with PNA. When the sections were first incubated with neuraminidase all these tumours were positive with PNA. Six adrenocortical tumours and 7 neuroblastomas were examined and found to be negative with PNA with or without neuraminidase pre-treatment. Seven carcinoid tumours were examined and found to be positive with PNA only in tubular areas and negative in solid areas; pre-treatment with neuraminidase did not alter the staining pattern. Immunoreactivity for NSE was absent in only 1 of the neuroendocrine tumours. A higher proportion of neuroendocrine tumours was positive with anti-chromogranin than with anti-synaptophysin.