PMC5405369_01
The histology and immunohistochemistry of a lymph node. (a) Gross examination of the lymph node architecture shows prominent vessels, suggesting the formation of the arborizing high endothelial venules. (b) The expanded CD21-positive follicular dendritic cell meshworks. (c) Hematoxylin and eosin stain showing polymorphous background infiltrate composed of medium sized atypical lymphocytes and enlarged pleomorphic cells with unilobated nuclei and prominent nucleoli, resembling RS-like B-cells. (d) The RS-like B-cells have less prominent CD20 expression in comparison to the B-lymphocytes present in the polymorphous infiltrate. (e) The RS-like B-cells are CD30-positive with characteristic paranuclear dot-like staining. (f) The lymphoid population consists of the CD2-positive atypical T-lymphocytes that often form rosettes around RS-like B-cells. (g) and (h) Atypical T-lymphocytes are CD10- and BCL6-positive.
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Microscopic examination revealed effacement of the normal nodular architecture with predominantly small-sized lymphoid cells with cleaved nuclei and scant cytoplasm distributed among a polymorphous background infiltrate including small lymphocytes, eosinophils, plasma cells, and histiocytes (Figure 1(c)). Enlarged cells resembling Hodgkin-like cells or RS-like B-cells with abundant pale cytoplasm and unilobated and enlarged nuclei with prominent eosinophilic nucleoli were noticed (Figure 1(c)). Evident proliferation of arborizing high endothelial venules was observed (Figure 1(a)). T-lymphocytes that were also CD2-, CD4-, and CD5-positive (Figure 1(f)). The number of CD4-positive T-lymphocytes was markedly increased compared to CD8-positive T-lymphocytes. Atypical T-lymphocytes were CD10- and B-cell lymphoma 6- (BCL6-) positive, indicative of T-follicular helper (TFH) phenotype (Figures 1(g) and 1(h)). The RS-like B-cells were CD20- and CD30-positive (Figures 1(d) and 1(e)). The CD21 stain revealed the preexistent follicular dendritic networks ("burn out" lymphoid follicles); however an expansion of those networks with the formation of enlarged nodular structures was also seen (Figure 1(b)).
EBER-ISH of lymph node and bone marrow. (a) and (c) Positive controls of lymph node and in bone marrow, respectively. (b) and (d) Negative EBER-ISH in the lymph node and bone marrow of the current patient, respectively.
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The Epstein-Barr encoding region in situ hybridization (EBER-ISH) was negative (Figure 2). EBER-ISH was negative (Figure 2).
Histology and immunohistochemistry of bone marrow. (a) Hypercellular bone marrow with prominent lymphoid infiltration. (b) Atypical CD3-positive T-lymphocytes. (c) Enlarged pleomorphic cells with unilobated nuclei and prominent nucleoli, resembling RS-like B-cells. These cells show less pronounced expression of CD20 compared to normal B-lymphocytes (a CD20-positive small cell population in the background). (d) The RS-like B-cells are CD30-positive with characteristic paranuclear dot-like staining.
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The premortal bone marrow biopsy showed hypercellularity with marked interstitial infiltration of small lymphocytes with cleaved nuclei and scant cytoplasm (Figure 3(a)). These lymphocytes were CD3-positive and were organized in paratrabecular clusters together with a high number of CD68-positive histiocytes and eosinophils (Figure 3(b)). The CD20- and CD30-positive RS-like B-cells were distributed within this population (Figures 3(c) and 3(d)).