Xanthomatous hypophysitis.

Xanthomatous hypophysitis (XH) is the rarely seen primary form of hypophysitis. The histological differential diagnosis includes other causes of hypophysitis, Erdheim-Chester disease (ECD), Langerhans cell histiocytosis, Rosai-Dorfman disease and plasma cell granulomas. We present a 39-year-old woman admitted to our department with headache, menstrual irregularity and galactorrhea. The MRI revealed a lesion with a central cystic/necrotic region and a diameter of almost 1cm. Histologic examination showed an inflammatory infiltrate of numerous foamy histiocytes, surrounding the necrotic tissue. On immunohistochemical sections, infiltrating foamy cells stained strongly positive for CD68, and negative for CD1a and S100. After establishing the diagnosis of XH, the patient underwent glucocorticoid treatment. XH should be considered in the differential diagnosis of pituitary lesions. Since XH is rare, it is difficult to assess the efficacy of medical/surgical treatment of this entity accurately.