Sex steroid receptor expression in 'carcinoid' tumours of the breast.

Nine 'carcinoids' of the breast (argyrophilic carcinomas) were examined for the presence of estrogen receptor (ER), progesterone receptor (PR), and androgen receptor (AR), using immunohistochemistry. The tumours were selected on the basis of their histo-morphological appearance and positive Grimelius stain. All cases were immunoreactive for neuron-specific enolase (NSE). In one case the tumour cells were intensely chromogranin A positive. All cases were ER positive, while 5 cases expressed AR and 5 cases PR. Immunostaining for ER and simultaneous demonstration of argyrophilia or chromogranin A expression in chromogranin A positive argyrophilic carcinoid tumour of the breast provided further evidence that neuroendocrine cells in breast tumours express sex steroid receptors. The similarity in sex steroid receptor expression pattern in 'carcinoids' of the breast and the more common categories of breast cancer suggests an identical responsiveness to endocrine therapy.