MON-237 Primary Pituitary Lymphoma - an Unusual Guest in the Sella!

Background Primary Pituitary Lymphoma (PPL) is a rare differential diagnosis for a sellar / suprasellar lesion. Less than 40 cases have been reported. Case presentation A 75-year old Chinese lady with known subclinical hypothyroidism presented with 3-day history of dull frontal headache, giddiness and diplopia. Incomplete left cranial nerve (CN) III palsy was noted with no other neurological deficit or hemodynamic instability. MRI brain and pituitary showed a T1- and T2 isointense, 2.0 x 1.1 x 1.3 cm enhancing mass arising from the left sellar region, extending to the left sphenoid and cavernous sinuses, displacing the pituitary stalk towards the right, with no optic chiasm compression. There was no imaging evidence of apoplexy. Evaluation of anterior pituitary hormones revealed hypocortisolism (peak cortisol post 1mcg Synacthen 344 nmol/L, ACTH 3.5 ng/L [10 - 60]), subclinical hypothyroidism (free T4 9.6 pmol/L [8.8 - 14.4], TSH 7.19 mU/L [0.65 - 3.70]), normal prolactin 7.4 ug/L [5.0-27.7], mildly elevated IGF-1 193.7 mcg/L [67.0 - 189.0] with normal GH 1.0 ng/ml, and elevated FSH appropriate for menopause. Glucocorticoid replacement was started. Though the clinical presentation was not typical of a pituitary macroadenoma, in view of symptomatic improvement and neurological stability, she was conservatively managed with plans for early repeat imaging outpatient. Patient was readmitted 1 month later for headache and decreased left-sided visual acuity. A complete CN III palsy, and new CN II, IV and VI deficits were noted (orbital apex syndrome). Repeat MRI showed increase in the size of the sellar lesion to 2.6 x 2.1 x 1.3 cm, surrounding the optic nerve and with left cavernous and sphenoid sinus invasion. Again, there was no suggestion of apoplexy. Biopsy of the lesion was performed, and histology was consistent with Diffuse Large B-cell Lymphoma and Grade 3A Follicular Lymphoma with high proliferative index (Ki67 70%). Immunohistochemistry excluded carcinoma, meningioma and pituitary tumor. PET-CT and bone marrow aspirate confirmed the diagnosis of PPL without metastasis. After 3 cycles of chemotherapy (Methotrexate, Rituximab, Cyclophosphamide, Doxorubicin, Vincristine and Prednisolone), significant decrease in the size of the lesion was noted on repeat MRI. Only mild asymmetric soft tissue thickening remained noticeable over the left sella and cavernous sinus. Cranial nerve deficits had since completely resolved. Glucocorticoid replacement was continued in the meantime while awaiting the completion of chemotherapy. Conclusion PPL may present in a similar manner as pituitary apoplexy. Absence of typical imaging characteristics of apoplexy in patients with rapid symptom progression and CN involvement should alert clinicians to consider alternative diagnosis including aggressive neoplastic, inflammatory and infective lesions.