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Extensive extraaxial prominently enhancing mass encases the left frontal lobe with thickened T2 and FLAIR hyperintense dura extending to involve the falx, occluding the anterior 1/3 of the superior sagittal sinus, crossing the midline over the right frontal lobe, and extending inferiorly over the left frontal lobe to the floor of the anterior cranial fossa.
In addition, there is a focal area of enhancement in the subarachnoid space. The tissue shows low ADC values and is relatively hypointense on T2.
The characteristics of the extra-axial mass are consistent with tumor and the favored diagnosis is lymphoma.
The patient went on to have an open dural biopsy.
Sections show small fragments of a densely cellular tumor composed of solid sheets of small to medium-sized lymphocytes. The tumor cells contain round nuclei with fine granular chromatin and inconspicuous nucleoli. No follicles or germinal centers are seen. No granulomas are identified.
Immunohistochemical results show a predominantly CD20+/CD79a+/CD5+/BCL2+ B-cell tumor cell population with negative staining for CD10, CD23, CD138, CD43, BCL6 and CyclinD1. The tumor cells demonstrate kappa-ISH light chain restriction. There is a background population of CD3 positive T-cells. The Ki67 proliferation index is approximately 10%.
FINAL DIAGNOSIS: Low-grade B-cell non-Hodgkin lymphoma.
Comment: The histological and immunohistochemical features are those of a low grade CD5+ B-cell non-Hodgkin lymphoma, favoring chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).