Extranodal NK/T-cell lymphoma presenting as a pituitary mass. Case report and review of the literature.

Primary pituitary lymphomas (PPLs) are rare tumors of the central nervous system, and most are of B-cell origin. Extranodal NK/T-cell lymphomas are uncommon neoplasms that are highly aggressive and show a strong association with Epstein-Barr virus. They most commonly affect the nasal cavity and paranasal sinuses; manifestation as a primary pituitary tumor has never been described. The authors report a case of NK/T-cell lymphoma of the pituitary gland and review 17 cases of PPL from the literature. All patients had been evaluated at presentation for clinical, neuroimaging, and histopathological findings. Patients who had systemic lymphoma with secondary involvement of the pituitary gland were excluded. The mean patient age was 55.5 years (range 26-86 years); the male/female ratio was 13:5. The most common presentation was pituitary insufficiency (72%), followed by headache (56%), diplopia (39%), visual loss (28%), and fever (22%). Thirteen patients (72%) exhibited anterior hypopituitarism and seven (39%) had diabetes insipidus at presentation. Magnetic resonance imaging demonstrated enhancing parasellar masses with diffuse enlargement of the pituitary gland (94%), suprasellar extension (44%), cavernous sinus extension (39%), and stalk thickening (22%). Thirteen patients (72%) had B-cell lymphoma, four (22%) had T-cell lymphoma, and one (6%) had NK/T-cell lymphoma. Primary pituitary lymphomas are rare entities with a range of clinical presentations and neuroimaging findings that are unique from those of patients who present with pituitary adenomas. The pathological entity of NK/T-cell lymphoma is distinct, and its course is very aggressive with a poor prognosis.