A 26-year-old male presented with blurred vision and headaches. He had bitemporal hemianopia with visual acuity 6/9 and 6/12 in right and left eyes, respectively. MRI revealed large sellar/suprasellar mass 51x56x24mm. Prolactin was 489000mU/L(<278). Cabergoline was commenced at 0.5mg twice weekly. Two weeks later, visual acuity had improved, Prolactin declined to 46microg/L(<15) and tumour shrunk (33x30x34mm). Cabergoline was increased to 0.5mg thrice weekly. Acute visual loss occurred 6 weeks later. The sellar mass had rapidly expanded (32x40x42mm), with no radiological evidence of haemorrhage. Prolactin was 888mU/L(<278). He proceeded to emergent operation, which demonstrated diffuse organised haematoma.
Differential diagnoses for rapid Prolactinoma growth include Cabergoline resistance, intratumoral haemorrhage, lymphoma, malignant and metastatic disease. Incidence of apoplexy is reported between 2-7%. Recognised risk factors include: adenoma size and change in size, Dopamine Agonist (DA) therapy, anticoagulation, diabetes mellitus, hypertension, head trauma, and radiotherapy. In untreated adenomas, it is proposed that rapid tumour expansion outstrips the gland’s blood supply, leading to ischaemia and haemorrhagic infarction. DA cause apoptosis of lactotrophs, with associated fibrosis. Tumour shrinkage is suggested as a mechanism for intratumoural haemorrhage.
Giant Prolactinomas are defined by maximal diameter ≥40mm (with massive extrasellar extension), Prolactin >1000mg/L, and absence of concomitant hormone secretion. DA are first line therapy and cause significant shrinkage in 68-74%, and hormonal response in 60-63% of patients. Improvements in visual fields have been reported in 96% of cases, with normalisation in 48%. Rapid tumour shrinkage has been associated with CSF leak, internal haemorrhage, apoplexy, and chiasmal herniation. Apoplexy has been described in patients with varied tumour size, DA dosage, and time from treatment initiation. Goal of therapy is to maximise neurological recovery while minimising risk of complications from rapid shrinkage, however there is a paucity of literature regarding optimal DA dose titration in this clinical context.