Accurate quantification of malignant cells in the peripheral blood of patients with cutaneous T-cell lymphoma is important for early detection, prognosis, and monitoring disease burden.

We sought to determine the spectrum of current clinical practices; critically evaluate elements of current International Society for Cutaneous Lymphomas (ISCL) B₁ and B₂ staging criteria; and assess the potential role of T-cell receptor-Vβ analysis by flow cytometry.

We assessed current clinical practices by survey, and performed a retrospective analysis of 161 patients evaluated at Yale (2011-2014) to compare the sensitivity, specificity, positive predictive value, and negative predictive value of parameters for ISCL B2 staging.

There was heterogeneity in clinical practices among institutions. ISCL B₁ criteria did not capture 5 Yale cohort cases with immunophenotypic abnormalities that later progressed. T-cell receptor-Vβ testing was more specific than polymerase chain reaction and aided diagnosis in detecting clonality, but was of limited benefit in quantification of tumor burden.

Because of limited follow-up involving a single center, further investigation will be necessary to conclude whether our proposed diagnostic algorithm is of general clinical benefit.

We propose further study of modified B₁ criteria: CD4/CD8 ratio 5 or greater, %CD4⁺ CD26⁻ 20% or greater, or %CD4⁺ CD7⁻ 20% or greater, with evidence of clonality. T-cell receptor-Vβ testing should be considered in future diagnostic and staging algorithms.