From the Guidelines
When suspecting cutaneous lymphoma, the most critical blood tests to check include a complete blood count (CBC) with differential, lactate dehydrogenase (LDH), comprehensive metabolic panel, and flow cytometry to detect abnormal lymphocytes in the blood, as recommended by the most recent guidelines 1.
Key Blood Tests for Cutaneous Lymphoma
The following blood tests are essential for diagnosing and staging cutaneous lymphoma:
- Complete blood count (CBC) with differential
- Lactate dehydrogenase (LDH)
- Comprehensive metabolic panel
- Flow cytometry to detect abnormal lymphocytes in the blood
Specific Tests for Mycosis Fungoides and Sézary Syndrome
For mycosis fungoides and Sézary syndrome, the most common types of cutaneous T-cell lymphoma, additional tests should be ordered, including:
- Sézary cell count
- T-cell receptor gene rearrangement studies
- HTLV-1 antibody testing to rule out adult T-cell leukemia/lymphoma, as suggested by 1 These tests help assess for blood involvement, which impacts staging and prognosis. Elevated LDH often indicates more aggressive disease or larger tumor burden.
Importance of Skin Biopsies
While these blood tests are important, they should complement skin biopsies, which remain the gold standard for diagnosis. The presence of atypical lymphocytes in peripheral blood (Sézary cells) particularly suggests leukemic involvement in cutaneous T-cell lymphoma and indicates more advanced disease requiring more aggressive treatment approaches, as noted in 1 and 1.
From the Research
Blood Tests for Suspected Cutaneous Lymphoma
The following blood tests may be useful in diagnosing cutaneous lymphoma:
- Flow cytometry to detect T-cell receptor (TCR) clonality and evaluate T-cell receptor-Vβ chain restriction 2
- Gene rearrangement analysis, such as polymerase chain reaction (PCR), to detect clonality 3, 4
- Immunophenotyping to evaluate the presence of abnormal T-cell or B-cell populations 2
- Complete blood count (CBC) to evaluate for signs of lymphoma, such as anemia, thrombocytopenia, or leukocytosis
- Lactate dehydrogenase (LDH) levels, as elevated LDH is a poor prognostic factor in erythrodermic cutaneous T-cell lymphoma 5
- Sézary cell count, which can be determined manually or by flow cytometry, to evaluate the extent of blood involvement in cutaneous T-cell lymphoma 5
Specific Markers and Tests
Some specific markers and tests that may be useful in diagnosing cutaneous lymphoma include:
- CD4/CD8 ratio, which can be elevated in cutaneous T-cell lymphoma 2
- CD26 and CD7 expression, which can be decreased in cutaneous T-cell lymphoma 2
- Immunoglobulin H (IgH) gene rearrangement analysis, which can be used to detect B-cell clonality 4
- T-cell receptor (TCR) gene rearrangement analysis, which can be used to detect T-cell clonality 3, 2
Limitations and Future Directions
While these blood tests can be useful in diagnosing cutaneous lymphoma, they have limitations and should be used in conjunction with other diagnostic tools, such as skin biopsies and clinical examination. Further study is needed to develop more sensitive and specific tests for cutaneous lymphoma, particularly for early-stage disease 3, 2.