Related Experiment Video
Updated: Aug 12, 2026
VDJ-Seq: Deep Sequencing Analysis of Rearranged Immunoglobulin Heavy Chain Gene to Reveal Clonal Evolution Patterns of B Cell Lymphoma
Published on: December 28, 2015
Cutaneous lymphoma-simulating Merkel cell carcinoma-molecular genetic demonstration of a clonal disease with
1Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Insights
Polymerase chain reaction (PCR) and sequencing confirmed two leg tumors, initially appearing distinct, originated from the same B-cell lymphoma clone. This highlights PCR
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Undifferentiated cutaneous round cell tumors present diagnostic challenges, with Merkel cell carcinoma and malignant lymphoma as key differential diagnoses.
- Immunohistochemistry is crucial for evaluating these tumors, but can have limitations.
Observation:
- A 73-year-old man presented with cutaneous large cell lymphoma in the right leg and a left leg tumor mimicking Merkel cell carcinoma.
- Initial immunophenotyping of the left leg lesion showed absence of leukocyte antigens and focal expression of keratin and NSE, contrasting with the right leg lymphoma.
Findings:
- Polymerase chain reaction (PCR) analysis of DNA from both lesions revealed clonal rearrangements of the immunoglobulin heavy chain.
- Cloning and sequencing demonstrated high homology between the DNA products from both lesions, confirming they originated from the same B-cell lymphoma clone.
Implications:
- This case underscores the diagnostic value of PCR and sequencing in definitively characterizing lymphoproliferations.
- It illustrates the potential limitations of immunophenotyping in complex cases and emphasizes the need for complementary molecular techniques.
Abstract:
Merkel cell carcinoma and malignant lymphoma are important differential diagnoses for undifferentiated cutaneous round cell tumors and immunohistochemistry is instrumental in their evaluation. We describe a case of a 73-year-old man who had cutaneous large cell lymphoma in the right leg (immunophenotype CD45+, CD19+, CD20+ CD22+, lambda clonal, cytokeratin-, NSE-) and lymphoma in left leg simulating Merkel cell carcinoma showing absence of leukocyte antigens (CD45-, CD20-, no light chains) and focal expression of keratin and NSE. However, analysis of polymerase chain reaction amplification products of DNA extracted from both lesions showed two amplifiable sharp bands indicating clonal rearrangements of both alleles of the immunoglobulin heavy chain. Cloning and sequencing of the products from left and right leg lesions showed either 100% homology (one band), or close similarity (the other band), indicating that both tumors were derived from the same B-cell lymphoma clone. This case shows the value of polymerase chain reaction and sequencing in analyzing the ultimate nature of lymphoproliferations and illustrates the potential limitations of immunophenotyping.
