Xanthomatous Hypophysitis: Always Think Twice Before Pituitary Resection

A 47-year-old male with symptoms of low libido, hair loss, increased thirst, and nocturia was initially referred for pituitary adenoma resection. Laboratory tests revealed hypopituitarism and central diabetes insipidus (DI), and an MRI showed an enlarged pituitary gland without stalk thickening. The patient's symptoms and MRI findings did not align, prompting a biopsy instead of resection. The biopsy revealed xanthomatous hypophysitis, characterized by clusters of foamy macrophages and positive immunohistochemistry for CD3, CD20, CD138, and CD68, but negative for IgG4. The patient was treated with hormonal replacement therapy, avoiding unnecessary surgery. This case highlights the importance of considering xanthomatous hypophysitis, a rare condition with only 36 reported cases, as a differential diagnosis in pituitary disorders, especially when clinical and imaging findings do not match.