Hematopathology
Contributed by Shweta Bhavsar, MBBS, MD and Nathanael G. Bailey, MD
CLINICAL HISTORY
The patient is a male in his early 60s, presenting with worsening fatigue, found to have diffuse lymphadenopathy and pleural effusions diagnosed as stage IV follicular lymphoma grade 1-2 of 3 with pleural effusions and bone marrow involvement. He was treated with six cycles of bendamustine and rituximab with complete response followed by observation. 20 months post completion of therapy the patient presented with an enlarged right groin lymph node with CT scans showing extensive lymphadenopathy consistent with relapsed lymphoma. The patient was lost to follow up presenting 5 months later with significant B symptoms and repeat CT scans showing worsening lymphadenopathy, splenomegaly and pleural effusion, treated with six cycles of R-CHOP. Post therapy imaging showed complete response. Patient refused maintenance rituximab. 3 and a half years later presented to the ER with 10 pound weight loss, fatigue, and 2 new neck masses of 2-3 weeks duration. CT scan showed extensive lymphadenopathy, clinically suspicious for recurrent lymphoma. Right cervical lymph node excisional biopsy was performed and sent for histopathologic evaluation.
MICROSCOPY
On histopathologic evaluation, the lymph node architecture was largely effaced by a diffuse proliferation of large lymphoid cells with irregular nuclear contours, vesicular chromatin and prominent nucleoli (Figure 1). Many mitoses and apoptotic figures were present. Apparently normal lymphoid tissue with follicular patterns was identified at the edge of the specimen.
Immunohistochemical stains (Figure 2 and Figure 3) showed that the large lymphoid cells were positive for CD20, BCL6, MUM1, Cyclin D1, BCL2, CD10 showed some weak staining in the large lymphoid cells (< 30% of cells) and were negative for CD3, CD5, SOX11 and TdT . MYC staining was seen in ~30% of the lymphoid cells. CD21 highlighted follicular dendritic cell meshworks in adjacent normal lymphoid tissue. Ki67 stain showed a high proliferative fraction with greater than 90% positive cells.
Flow cytometric immunophenotypic studies (Figure 4) performed on the right cervical lymph node identified a large population (approximately 51.6% of cellular events) of CD20 positive, CD19 positive, CD10 negative, CD5 negative, lambda light chain restricted B-cells consistent with B-cell lymphoma. Additional cells identified included few histiocytes, heterogeneous T-cells with decreased CD4:CD8 ratio (0.1:1), and a subset of T-cells expressing CD16&57 positivity.
Fluorescence in situ hybridization (FISH) studies (Figure 5) demonstrated the presence of BCL2 (66.2% cells) and CCND1 (88.3% cells) rearrangements, a likely rearrangement of BCL6 with loss of the 5' signal (~49% cells), and no rearrangement of MYC, with negative results for both MYC break apart and IGH/MYC probes.