4/26/2005 Case 3: Primary intracerebral plasmacytoma

Clinical History:

83 year old woman with remote history of gastric carcinoma and recent history (within one year) of ductal breast carcinoma experienced an episode of confusion with loss of speech. She recovered from this. An MRI scan showed a 1 cm enhancing nodule in the left parietal lobe with surrounding T2 abnormality (called "edema") and mass effect; and a second, smaller lesion in the right insula. Workup for other sites of metastatic disease was all negative. A stereotactic biopsy of the left parietal mass was performed, and is represented on the slides distributed.

Diagnostic Notes:

The biopsy showed brain tissue infiltrated and replaced by a mass of relatively small cells; these were a fairly homogeneous population of plasma cells, some mature, some immature. There was a hint of perivascular cuff formation resembling lymphoma in the brain, and there was some more diffuse infiltration as single cells into the brain. Focally there were hemosiderin deposits.

The diagnosis was straightforward if unusual: a primary CNS plasmacytoma, and clearly neither metastatic gastric carcinoma nor metastatic breast carcinoma.
Immunostains for light chains had excessive background, but NYU Hematopathology did in-situ hybridization for kappa and lambda light chain mRNA and showed that the mass was a clonal population of kappa-positive plasma cells. The diagnosis is thus verified as Plasmacytoma. There are very few case reports of primary intracerebral plasmacytoma; they indicate a relatively favorable prognosis, with no evidence of spread as multiple myeloma later. In this patient an extensive workup disclosed no other evidence of disease, and she remained well six months after diagnosis of the intracerebral lesion.

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