Endocrine Abstracts

Case History: A 52 year old man presented in 2009 with a gradual loss of peripheral vision associated with headaches. Examination confirmed bi-temporal hemianopia. Further investigation revealed elevated prolactin levels and pituitary MRI showed evidence of large pituitary tumour. A diagnosis of macroprolactinoma was made and cabergoline was commenced. Given resistance to medical treatment, the patient required two surgical resections (2011 and 2013) and radical radiotherapy (2013). Between 2014 and 2017, his prolactin levels remained well controlled on cabergoline. However in 2018, prolactin levels increased and were resistant to increasing doses of cabergoline. Repeat pituitary MRI showed no evidence of tumour regrowth. The patient later developed neck pain associated with bilateral upper limb paraesthesia and hypoesthesia of the right upper limb. A spine MRI revealed an intradural extramedullary tumour at C2-C4 level. Surgical resection was performed and a diagnosis of pituitary carcinoma was made. Post-operatively prolactin levels normalised and cabergoline was weaned.

Investigations: Initial prolactin levels were approximately 30,000 mIU/L. MRI showed an invasive pituitary tumour. Histology confirmed a prolactinoma with high mitotic activity. Following surgical treatment and radiotherapy, his prolactin level remained within the normal range on ≤0.5 mg cabergoline weekly and MRI confirmed no tumour re-growth. In 2018, his prolactin level rose to 22,000 mIU/l despite 4.5 mg cabergoline/week. Repeat pituitary MRI confirmed no evidence of tumour re-growth. MRI spine revealed a 31×10×25 mm intradural extramedullary lesion between C2-C4 with cord compression. Histology revealed a pituitary tumour with atypical features including nuclear pleomorphism, increased mitotic activity, raised Ki-67 of 15-20%, and evidence of MGMT methylation.

Treatment: Initial treatment involved dopamine agonists i.e. cabergoline. However, given the resistance to medical treatment, the patient underwent transsphenoidal surgery followed by a craniotomy 2 years later. Post-surgical radiotherapy was initiated after the second procedure. Due to the development of cervical myelopathy secondary to intraspinal metastasis, the patient underwent a cervical decompression procedure followed by cervical radiotherapy. A trial of Temozolomide was ceased after 2 cycles, given intolerance to treatment.

Conclusion and Point for discussion: Pituitary carcinomas are rare neoplasms that metastasize to sites distant from the pituitary, accounting for approximately 0.1% of pituitary tumours. Pituitary carcinomas are challenging as they initially behave in a similar fashion to their benign counterpart at the outset. This case demonstrates the importance of considering metastatic disease in patients with rising prolactin levels and no evidence of sellar recurrence.