[Intrasellar xanthogranuloma with abscess formation in a patient with Rathke's cleft cyst].

An 80-year-old woman diagnosed with granulomatosis with polyangiitis (GPA) complained of a sustained, non-pulsatile headache. Her brain MRI diffusion-weighted images revealed a high-signal-intensity, space-occupying lesion in the sellar region that was rim-enhanced on gadolinium-enhanced T-weighted images. Pituitary involvement of GPA was initially suspected based on her condition; however, an abscess formation within an existing Rathke's cleft cyst was also considered according to a previous MRI finding that had been conducted for an unrelated purpose. A trans-sphenoidal resection of the lesion revealed an abscess with foam cells. These findings were consistent with a diagnosis of a xanthogranuloma with abscess formation in the Rathke's cleft cyst, and her headache was completely resolved without any immune therapy that is required for GPA. Thus, differential diagnosis of space-occupying lesions in the seller region should include xanthogranuloma with abscess formation, especially if a Rathke's cleft cyst is detected as an antecedent finding.