#dermpathJC December 2017:
Thursday, December 28th, 9pm EST
Article discussed: Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type. Diagnostic Considerations
Authors: Alexandra Hristov.
Archives of Pathology and Laboratory Medicine, 2012; 136: 876–881.
Open access article, PDF available at: http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2012-0195-RA?code=coap-site
Summary author: Dr. Silvija P. Gottesman (@SGottesmanMD).
Journal Club Summary:
Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type (PCDLBCL-LT), was recognized 20 years ago as a unique diagnostic entity, with exclusive involvement of the leg, intermediate prognosis and a diffuse dermal infiltrate of large B-cells.
PCDLBCL-LT – involves lower legs of women, F:M ratio is 2-4 : 1, median age 70s. However, 10-20% of the time, other parts of the body may be involved. Most common spread is to lymph nodes, bone marrow and the CNS. 50% survival at 5 years.
PCDLBCL-LT histology findings: grenz zone, diffuse sheets of large B-cells in the dermis, large centrocytes, centroblasts and immunoblasts. Mitotic figures are easily identified. T-cells are sparse.
PCDLBCL-LT markers: B-cell (CD19, CD20, CD22, CD79a, PAX-5), also BCL2, IRF4/MUM1 and FOXP1. This IHC profile may also be seen in other diffuse large B-cell lymphomas that involve the skin secondarily.
WHO notes 10% of PCDLBCL-LT do not express BCL2 or IRF/MUM1. Some classify BCL2- DLBCL of the skin as “primary cutaneous DLBCL, other.”
PCDLBCL-LT also commonly express BCL6, but typically lack CD10. IgM is another sensitive marker but may be difficult to interpret.
Primary cutaneous follicle center cell lymphoma vs EBV diffuse large B-cell lymphoma of the elderly vs Lymphomatoid granulomatosis. Figure below:
PCDLBCL-other should be used to describe rare cases of primary cutaneous T-cell and histiocyte-rich large B-cell lymphoma, or cases of intravascular large B-cell lymphoma or plasmablastic lymphoma that are limited to the skin at presentation.
Primary cutaneous follicle center cell lymphoma (PCFCL) – most common primary cutaneous B-cell lymphoma. Affects older adults, men more common than women. Often on head/neck and trunk. Extracutaneous spread, in 10%, to lymph nodes and bone marrow. 95% survival at 5 years.
PCFCL involving the leg tends to have a worse outcome and more likely to express BCL2, MUM1, FOX-P1, and IgM.
Reactive T-cells often prominent in PCFCL and is a helpful feature in distinguishing it from PCDLBCL-LT.
Look for inside out follicles in pcFCL – Neoplastic follicle center cells surrounding small lymphocytes and abutting dermal collagen.
PCFCL – pan B-markers, BCL6, less commonly CD10. Disrupted follicular networks highlighted by CD21, CD23, or CD35. All marginal zone B cells are BCL2+ and BCL6-. Opposite is true for normal follicular B cells and those in pcFCL. If centrocyte like B cells in skin are BCL6+ and BCL2+ consider cutaneous involvement of systemic follicular lymphoma. Strong expression of CD10 and BCL2 is suggestive of cutaneous involvement of a systemic follicular lymphoma. MUM-1 usually negative in pcFCL and positive in pcDLBCL-LT.
EBV can lead to so many odd lymphoid proliferations in immunocompromised. Here are two examples below:
EBV-positive diffuse large B-cell lymphoma of the elderly – necrosis is common and a background mixed inflammatory infiltrate may be seen that includes histiocytes and plasma cells. Also BCL6+, CD30+, MUM1+ and some B-cell markers.
Lymphomatoid granulomatosis – skin involvement in 25-50% of patients, >90% will have pulmonary involvement, CNS is common too. Median survival of 2 years. It is angiocentric and angiodestructive, large EBV+ B-cells, necrosis and a mixed infiltrate. 
In the words of Dr Deeken: Lymphoma work-up: All of the CD’s and don’t forget the EBV 
#dermpath #hemepath
See you all next on 01/25/2018 at 9pm EST for another great journal club.
Thank you,
Silvija Gottesman, MD
