Presentation
Headaches.
Patient Data
A very vividly enhancing mass lesion involving the hypothalamus and chiasm has low T1 signal, fairly low T2 signal surrounded by edema, and profoundly low ADC values (670 x 10^-6 mm^2/s). The lesion is clearly separate to the pituitary, although the infundibulum is thickened. There are no flow voids within it. MR angiography is unremarkable.
Conclusion:
The hypothalamic/chiasmatic enhancing lesion clearly represents a tumor, and by far the most likely diagnosis is that of lymphoma given the enhancement and diffusion characteristics.
Case Discussion
The patient went on to have a biopsy.
Histology
Sections contain discohesive malignant cells infiltrating brain tissue. There is sheet-like growth of cells with small amounts of cytoplasm, containing enlarged irregularly shaped nuclei with coarse chromatin and frequently seen mitoses and apoptotic cells. Perivascular cuffing with tumor cells is also present.
Immunohistochemistry:
positive for CD20, PAX5, CD10, BCL6, MUM 1, BCL2. C-myc positive 60%
negative for CD5, CD3, CD23, cyclin D1, ALK, EBER ISH
Ki 67 is >95%.
FINAL DIAGNOSIS: diffuse large B-cell lymphoma. Germinal center phenotype.
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