Radiology Quiz 17468 | Radiopaedia.org

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Pituitary lymphoma is rare. Into what two main groups can pituitary lymphomas be divided?

As is the case with CNS lymphoma, pituitary lymphomas can be divided into primary pituitary lymphoma (no other disease; exceedingly rare) or secondary involvement of the pituitary from more widespread disease (as in this case).

Question 2

Pituitary lymphoma and pituitary macroadenomas can appear very very similar. What signal intensity difference may be apparent on MRI, and what is the histological cause?

Show Answer

Lymphomatous deposits are composed of very tightly packed cells with high nuclear to cytoplasmic ratio, which in turn results in relatively low signal on T2 weighted images (iso to hypointense) whereas macroadenomas tend to be hyperintense. This histological feature also results in hyperdensity on CT and relatively restricted diffusion on DWI.

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.