Presentation
Night sweats and pyrexia of unknown origin. CT of the chest abdoment and pelvis demonstrated equivocal splenomegaly.
Patient Data
PET scan demonstrates a focal region of increased uptake in the pituitary region. No other abnormal uptake identified in the rest of the body (not shown).
Pre-and post contrast scans were performed through the pituitary fossa including dynamic images (not shown). The pituitary is enlarged, measuring 10 x 10 x 11 millimeters in orthogonal planes. There is triangular tapering toward the infundibulum. The infundibulum demonstrates equivocal thickening with a possible focus of restricted diffusion within the superior part of the gland. A small 4 mm area of hypo enhancement is seen in the left inferior pituitary. The cavernous sinuses have a normal appearance.
- FDG PET increased uptake in the region of the pituitary (blue arrow).
- Enhancing enlarged pituitary extends up the infundibulum (yellow arrow) with probable thickening of the more superior infundibulum (orange arrow).
This patient went on to have a transphenoidal resection.
Histology
MICROSCOPIC DESCRIPTION: Paraffin sections show infiltration and destruction of pituitary acini by a population of atypical large lymphoid cells. These have enlarged round and oval vesicular nuclei, many with conspicuous nucleoli, and a narrow rim of pale cytoplasm. These are arranged in solid aggregates and diffuse sheets within and between acini. Scattered mitotic figures are noted within the atypical lymphoid cells. The atypical cells show strong membrane staining for CD20 and CD79a and perinuclear staining for Bcl-2. There is also strong diffuse nuclear staining for MUM1 in a moderate number of the atypical lymphoid cells. No staining for cyclin D1 or CD23 is seen. The features are of non Hodgkin's diffuse large B cell lymphoma.
FINAL DIAGNOSIS: Non Hodgkin's diffuse large B cell lymphoma.
Case Discussion
Incidental pituitary uptake on FDG PET is relatively uncommon found in ~0.1-1.0% of studies (depending on the population imaged). Of these a significant number (40-95%) are due to pathology and pituitary adenomas account for vast majority (~90%) 1-2. This case illustrates a rarer occurrence, namely lymphoma of the pituitary gland.