Endocrine Abstracts

Introduction: Giant prolactinomas are uncommon tumours and typically exceed 40 mm. These tumours are locally invasive but still respond to dopamine agonist therapy. The medical management of cystic giant prolactinomas with dopamine agonists is controversial as the non-solid components of these aggressive tumours are believed to respond poorly to drug therapy. We present a case of a giant cystic invasive prolactinoma masquerading as a multilobular schwannoma that was successfully treated with cabergoline.

Case report: A 35-year-old man presented with severe headaches, left sided lancinating facial pain and bitemporal hemianopia. MRI brain revealed 52 mm large irregular mixed solid and cystic mass involving the pituitary fossa with optic chiasmal compression. MR angiography showed encasement of the internal carotid, left anterior and middle cerebral arteries. The differential diagnosis included cystic craniopharyngioma or multilobular schwannoma. Serum prolactin was markedly elevated at 87 900 mIU/l (normal: 53–360 mIU/l) and associated with hypogonadotrophic hypogonadism (serum testosterone: 3.0 nmol/l, LH 1.4 IU/l, FSH 4.3 IU/l). Thyroid, adrenal and posterior pituitary function was normal. The marked hyperprolactinaemia was suggestive of macroprolactinoma.

Cabergoline was commenced and titrated to maintenance dose of 3 mg/week which resulted in a rapid fall in serum prolactin. There was complete resolution of the visual field deficit, headaches and facial neuropathic pain in twelve weeks. Repeat pituitary MRI scanning demonstrated a progressive and dramatic reduction in the size of the pituitary mass. Nadir serum prolactin was 141 mIU/l.

Conclusion: Giant cystic prolactinomas can be locally invasive and mimic other primary intracranial neoplasms. Surgery has historically been the mainstay of treatment of cystic pituitary tumours but this case demonstrates that carefully supervised medical therapy with dopamine agonists is an effective first line option for cystic macroprolactinomas. This strategy obviates the risks of pituitary surgery with its attendant complications and risk of postoperative hypopituitarism.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.