Endocrine Abstracts

Background: Primary pituitary lymphoma (PPL) is exceptionally rare and often mimics non-functioning pituitary adenomas (NFPAs) radiologically. Recognition is crucial to avoid misdiagnosis and inappropriate treatment. C1 esterase inhibitor deficiency has been associated with lymphoproliferative disorders and may predispose to PPL. Therefore, in patients with C1 esterase inhibitor deficiency presenting with pituitary lesions, PPL should be considered in the differential diagnosis.

Case: A 68-year-old lady with known C1 esterase inhibitor deficiency and MGUS presented with a 5–6-year history of intermittent facial and neck swelling, headaches, and transient visual obscuration. The swelling, often preceded by fatigue and myalgia, had been attributed to atypical angioedema. Extensive investigations revealed an incidental 1 cm sellar mass compressing the optic chiasm, radiologically compatible with a non-functioning pituitary adenoma. Given the visual involvement, she underwent endoscopic endonasal debulking in February 2024. Histology revealed sparse CD20-positive B-cell aggregates with Ki-67 <5%, consistent with extranodal marginal zone lymphoma (MALT type). Diagnosis was confirmed by molecular clonality testing. Systemic staging with CT thorax, abdomen, and pelvis showed no disseminated disease. She required no adjuvant therapy and remains under surveillance with endocrinology follow-up. Serial MRI scans have confirmed no recurrence to date.

Conclusion: Primary pituitary lymphoma should be considered when assessing atypical sellar lesions, especially in patients with underlying risk factors. Its clinical and radiological features can closely resemble non-functioning pituitary adenomas, and tumour grade cannot be reliably inferred from growth patterns on surveillance MRI. Definitive diagnosis requires histopathological confirmation. In this case, visual compromise necessitated surgery. A true wait-and-watch approach will rarely be undertaken, as such lesions are typically assumed to be NFPAs until growth or chiasmal compression warrants intervention. Pragmatically, patients are monitored until progression necessitates surgery. A multidisciplinary approach remains essential for accurate diagnosis and optimal management.