A Novel Entity: Primary Sellar Natural Killer/T-Cell Lymphoma

Objective: Natural killer (NK)/T-cell lymphomas are a rare form of lymphomas that typically occur in the nasal cavity and upper aerodigestive tract. To our knowledge, presentation as a pituitary primary without involvement of the paranasal sinuses has never been described. We report the first case of NK/T-cell lymphoma isolated to the pituitary and review 26 patients with primary pituitary lymphomas from the literature.

Design: Case report and retrospective review.

Methods: A 62-year-old man presented with diabetes insipidus, altered mental status, and general fatigue. MRI demonstrated a pituitary-based mass with suprasellar extension. Histopathology via biopsy revealed NK/T-cell lymphoma. A systematic PubMed search was performed to identify reports of primary pituitary lymphomas.

Results: In the PubMed search, the mean patient age was 56 years with male-to-female ratio of 1.7:1. Patients presented with symptoms of headache (62.5%), diplopia (41.7%), decreased visual acuity (29.1%), anterior pituitary dysfunction (75%), and posterior pituitary dysfunction (20.8%). Findings on examination included cranial nerve palsy (50%) and temporal hemianopsia (37.5%). Initial proposed diagnoses were pituitary adenoma (75%), infectious process (15%), and lymphoma (10%). Transsphenoidal biopsy was performed in all cases. B-cell lymphoma was diagnosed in 75% of patients, T-cell lymphoma in 20%, and one patient had a mixed B- and T-cell lymphoma.

Conclusions: Primary pituitary lymphomas are rare neoplasms with a propensity for direct invasion of surrounding structures. NK/T-cell lymphomas are an aggressive subtype of lymphoma that previously has not been described as causing isolated pituitary disease. Given their increasing frequency and poor prognosis with treatment delay, primary NK/T-cell lymphoma should be considered in the differential diagnosis of a pituitary mass.