CD5-Positive Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type: An Unusual Presentation

Area of Science:

• Hematology
• Oncology
• Dermatopathology

Background:

• Primary cutaneous diffuse large B-cell lymphoma-leg type (PCDLBCL-LT) is an aggressive non-Hodgkin lymphoma.
• CD5 expression in PCDLBCL-LT is rare and complicates diagnosis, broadening the differential to include other B-cell lymphomas.
• Accurate diagnosis is crucial for appropriate patient management and monitoring.

Purpose of the Study:

• To report a rare case of CD5-positive PCDLBCL-LT in an elderly female patient.
• To highlight the diagnostic challenges and management of this distinct PCDLBCL-LT subgroup.
• To emphasize the importance of CD5 testing in PCDLBCL-LT diagnosis.

Main Methods:

• Case report of a 70-year-old female with a lower extremity cutaneous nodule.
• Histopathological and immunohistochemical analysis including CD5, CD20, MUM1, BCL2, IgM, and cyclin D1.
• Fluorescence in situ hybridization (FISH) for MYC, BCL2, and BCL6 rearrangements.
• Treatment with R-CHOP chemotherapy followed by rituximab-bevacizumab for relapse.

Main Results:

• Histopathology revealed a pandermal diffuse infiltrate of atypical large B-cells.
• Immunohistochemistry confirmed a CD5+, CD20+, MUM1+, BCL2+, IgM+, cyclin D1- profile, supporting CD5+ PCDLBCL-LT.
• FISH results were negative for MYC, BCL2, and BCL6 rearrangements, ruling out double-hit/triple-hit lymphoma.
• The patient achieved initial complete response with R-CHOP, followed by relapse and a second complete remission with rituximab-bevacizumab.

Conclusions:

• CD5 positivity defines a distinct subgroup of PCDLBCL-LT requiring careful diagnostic consideration.
• Routine CD5 testing is essential for accurate diagnosis and differential diagnosis of PCDLBCL-LT.
• This case underscores the importance of vigilant monitoring and tailored treatment strategies for CD5+ PCDLBCL-LT.