A 75-year-old woman was found to have a pituitary macroadenoma on MRI after presenting to her GP with visual disturbance, fatigue and a serum Na 129 mmol/L.
Examination revealed bitemporal hemianopia, and no features of pituitary hormone excess or deficiency. Laboratory findings were consistent with panhypopituitarism and a mildly elevated prolactin 1924 mIU/L likely related to stalk compression.
MRI revealed a 20x17x18mm lobulated enhancing soft tissue lesion in the pituitary fossa suggestive of pituitary macroadenoma, extending into the suprasellar cistern and impinging on the optic chiasm, with compression of the pituitary stalk.
She underwent uncomplicated transphenoidal secretion of her pituitary tumour 5 weeks later, that resulted in rapid complete resolution of visual field defect.
Histopathology surprisingly revealed a diagnosis of pituitary spindle cell oncocytoma (SCO). There were sheets and nodules of cells with ovoid to spindle nuclei and a moderate to large amount of brightly eosinophilic coarsely granular cytoplasm. Ki-67 index was 2%. Tumour cells stained positively for S100 and TTF-1 and negative for pituitary hormones.
SCO arises from the folliculostellate cells of the pituitary and is a benign non-endocrine neoplasm that accounts for only 0.1-0.4% of all sellar tumours.
These tumours are often indistinguishable clinically and macroscopically from non-functioning pituitary adenomas (NFA). However, there are two important points to note about SCO. First, these tumours are highly vascular and are associated with an increased risk of haemorrhage, at surgery. Second, preoperative diagnosis is therefore desirable. T1- and T2-weighted MRI may show hypointense foci and linear signal void areas in these tumours. Additionally, intense contrast enhancement can be seen during early stages of dynamic contrast enhanced MRI.
As with NFA, surgery is the cornerstone of management of SCO especially with visual field compromise. With complete surgical resection of the tumour, recurrence rates are low; however longer-term surveillance is required.