Morphologic changes of prolactin-producing pituitary adenomas after short treatment with dopamine agonists.

Treatment of patients with prolactin (PRL)-producing pituitary adenomas with dopamine agonists has proved successful for most cases. Dopamine agonists inhibit PRL secretion, suppress cell proliferation, and may induce apoptosis to adenoma cells. Dopamine agonists induce striking morphologic changes in the majority of treated PRL-producing adenomas. To date, these morphologic effects have been primarily described only after long-term treatment. To the best of our knowledge, no similar studies have investigated apoptotic alterations induced after short-term therapy. The purpose of this report is to describe the morphologic changes seen in PRL-producing adenomas after short-term dopamine agonist treatment. We present two cases of PRL-producing macroadenomas, both from male patients who received treatment with dopamine agonists, the first for 5 and the second for 8 days. In contrast to long-term treatment, no striking reduction of PRL immunoreactivity was noted. Slight stromal fibrosis was noted in case 1, which contained several cells all in late phase of apoptosis. In addition to typical apoptotic cells, numerous "dark" cells representing another common form of cell death were also noted. These novel findings represent characteristic features of short-term dopamine agonist treatment, which are not seen in long-term treatment.