Investigations
1st investigations to order
FBC
skin biopsy
Test
Biopsy of suspicious lesions is essential for all patients.[31][32] Multiple biopsies may be necessary to capture the pathological variability of disease. Analysis of the tumour should be done by a pathologist with expertise in the diagnosis of CTCLs.
Repeated biopsy may be necessary if the analysis of the consult material in conjunction with the clinical features is not diagnostic.[5][32]
Immunohistochemical (IHC) panel of skin biopsy should include CD2, CD3, CD4, CD5, CD7, CD8, CD20, CD30; molecular analysis to detect clonal T-cell receptor (TCR) gene rearrangements, or other assessment of clonality.
Tumour cells are usually CD3+, CD4+, and CD8-, although CD8+ variants are not uncommon. CTCL lesions often lose CD7.[5][32]
Repeated biopsy of skin should be done if the presence of large cell transformation (histologically as greater than 25% of the tumour cells displaying large size) or folliculotropism is suspected, but not previously confirmed pathologically.[32] The presence of either of these variants may have important implications for selection of therapy and outcome, and should be included in pathology reports.[32]
IHC panel of skin biopsy should include CD25, CD56, TIA1, granzyme B, TCRß, TCRẟ; CXCL13, inducible T-cell co-stimulator (ICOS), and PD-1.
Result
infiltration of atypical lymphocytes in epidermis and lining up at dermo-epidermal junction
clonal T-cell receptor rearrangement
Test
Helps to identify those patients with T-cell clones in peripheral blood, as a marker of tumour burden and prognosis. False negatives have been reported (rates of up to 20%) and may be due to technical aspects of PCR assay and/or scarcity of lymphocytic infiltrate in biopsy of early-stage lesions. Positive results do not necessarily equate with malignancy, as certain benign dermatoses may be clonal on PCR testing.
Result
detection of T-cell clone
flow cytometry
Test
Flow cytometric studies to assess and quantitate an expanded T-cell population with aberrant phenotype is recommended for patients with T2-4 skin classification, or any suspected extracutaneous disease including adenopathy, but is optional for patients with T1 stage disease.[5][31][32]
Result
lymphocyte subsets: expanded population of CD4+ T cells in peripheral blood; CD4/CD8 ratio ≥10
comprehensive metabolic panel
Test
Done to assess baseline function of the kidneys, prior to treatment.
Result
may be normal or deranged
LFTs
Test
Done to assess baseline function of the liver, prior to treatment.
Result
usually normal
serum lactate dehydrogenase
Test
May be elevated in systemic disease and is a strong predictor of poor prognosis in erythrodermic CTCL.
Result
usually normal
Investigations to consider
screen for Sézary cells on blood film
Test
Sézary cell preparation is less useful than flow cytometry due to the subjective nature of the process, but can be useful where flow cytometry is not available.[5][31][32] May be performed on thick or thin films. Result is subject to inter-observer variability. A quantitative count is more informative.
Result
>5% of circulating lymphocytes are atypical, cerebriform cells
human T-cell lymphotropic virus (HTLV)-I/2 serology
Test
HTLV-I/2 serology should be performed in all patients with mycosis fungoides or Sézary syndrome, to distinguish those with HTLV-I-associated adult T-cell leukaemia/lymphoma from those with other T-cell leukaemias, such as T-prolymphocytic leukaemia. This will have an impact on therapy.[5][32]
Result
positive or negative
bone marrow biopsy
lymph node biopsy
Test
If the skin biopsy is not diagnostic, biopsy of enlarged lymph nodes or suspected extracutaneous sites may be needed.[31][32] Excisional or incisional biopsy is the preferred method of lymph node biopsy.[32] A fine needle biopsy alone is not sufficient for the initial diagnosis of lymphoma.[32] Repeated biopsy may be necessary if results are not diagnostic.[32]
Result
staging tool
CT scan or PET
Test
CT with contrast of the neck, chest, abdomen, and pelvis (CAP) or integrated whole body (including legs and arms) with PET or CT is recommended for patients with T3 or T4 disease; and should be considered for patients with T2a, T2b, large-cell transformed disease, folliculotropic MF, palpable adenopathy, or abnormal laboratory studies.
Patients with cutaneous lymphomas may have extranodal disease, which may be inadequately imaged by CT. PET scan may be preferred in these circumstances. However, PET scans are not routinely recommended for patients with MF/SS in the UK.[5]
Result
staging tool
HIV test
Test
In the UK, all patients with suspected lymphoma should have an HIV test to distinguish those with HIV-associated malignancy.[5]
Result
positive or negative
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