1. Primary cutaneous B-cell lymphomas with large cell predominance–primary cutaneous follicle center lymphoma, diffuse large B-cell lymphoma, leg type and intravascular large B-cell lymphoma 
Charity B. Hope, Laura B. Pincus 
Seminars in Diagnostic Pathology 
Volume 34, Issue 1, Pages (January 2017)
DOI: /j.semdp
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2. Fig. 1
This case of primary cutaneous follicle center lymphoma shows multiple erythematous papules coalescing into a large plaque in the pre-auricular region of the face without overlying epidermal change. This is a typical clinical presentation of primary cutaneous follicle center lymphoma.
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3. Fig. 2
At scanning magnification, the diffuse pattern of primary cutaneous follicle center lymphoma shows a dense infiltrate without follicle formation extending throughout the entire dermis. The epidermis is spared.
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4. Fig. 3
At high power, most of the neoplastic cells are medium to large centrocytes with angulated, irregular nuclear contours. Rare centroblasts with round nuclei and vesicular chromatin are present as well. There are also scattered small reactive lymphocytes.
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5. Fig. 4
At scanning magnification, the follicular pattern of primary cutaneous follicle center lymphoma reveals a multinodular infiltrate of lymphocytes within the dermis, arranged in poorly formed, coalescing follicular structures. The epidermis is spared.
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6. Fig. 5
Neoplastic follicles are enlarged and irregular and lack well-formed mantle zones and light and dark zones are not present.
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7. Fig. 6
A high power view of a neoplastic follicle in follicular pattern primary cutaneous follicle center lymphoma reveals a predominance of large centrocytes with few centroblasts. Tingible body macrophages are not present.
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8. Fig. 7
This case of primary cutaneous follicle center lymphoma, diffuse type shows a typical immunophenotype for this disease with strong positivity for the B-cell marker CD20 (A); positivity for Bcl-6 (B); and negative staining for IgM and MUM-1 (C,D).
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9. Fig. 8
Immunohistochemical results for the case of primary cutaneous follicle center lymphoma, follicular pattern (H&E in Figs. 4–6). Bcl-6 strongly labels both neoplastic cells within follicles and small clusters within interfollicular zones (A), extending beyond CD21-positive dendritic cell networks (B); Bcl-2 is negative in neoplastic cells but highlights irregular mantle zones and admixed reactive T-cells (C); negative staining for MUM-1 is characteristic (D).
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10. Fig. 9
A case of primary cutaneous diffuse large B-cell lymphoma, leg type presenting as multiple bluish-red nodules and plaques on one leg. Both leg and non-leg sites can be involved in this disease.
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11. Fig. 10
At scanning magnification, primary cutaneous diffuse large B-cell lymphoma, this case of leg type shows dense sheets of cells extending through the full thickness of the dermis. The epidermis is spared.
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12. Fig. 11
A high power view of primary cutaneous diffuse large B-cell lymphoma, leg type, reveals sheets of large centroblasts and immunoblasts.
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13. Fig. 12
This case of primary cutaneous diffuse large B-cell lymphoma, leg type shows a characteristic immunohistochemical profile with strong positivity for CD20 (A); Bcl-2 (B); IgM (C); and MUM-1 (D).
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14. Fig. 13
Intravascular large B-cell lymphoma colonizing a benign vascular proliferation: Scanning magnification reveals a dome surfaced segment of skin with a vascular proliferation surrounded by epithelial collarettes.
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15. Fig. 14
Dilated vessels within the vascular proliferation contain large, atypical oval cells(A). Atypical cells have pale, vacuolated cytoplasm and large nuclei, some with prominent nucleoli. Numerous mitoses are present (B). A CD34 stain highlights the intravascular location of the atypical cells, and is negative in the cells of interest (C). Atypical cells are positive for CD20 (D).
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16. Fig. 15
Intravascular large B-cell lymphoma. The immunophenotype of intravascular large B-cell lymphoma may vary. This case shows positivity for CD10(A), as well as Bcl-2 (B), Bcl-6 (C) and CD5 (D).
Seminars in Diagnostic Pathology  , 85-98DOI: ( /j.semdp )
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