Demonstration of a dominant T-cell clone in skin biopsy specimens by a molecular assay constitutes an additional diagnostic criterion to differentiate cutaneous T-cell lymphomas (CTCLs) from inflammatory dermatoses.
To determine which patients, depending on their clinical presentations, could most benefit from a cutaneous T-cell clonality analysis in addition to histopathologic analysis for the diagnosis of CTCL.
Comparison of sensitivity and specificity of histopathologic analysis and a combination of this method and the detection of a T-cell receptor gamma chain gene rearrangement by polymerase chain reaction denaturing gradient gel electrophoresis performed on skin biopsy specimens obtained at initial presentation.
One hundred forty consecutive patients were classified into 4 groups, depending on their clinical presentation: (1) eczematous patches suggestive of early-stage mycosis fungoides (MF) (IA and IB of the TNM classification) (n = 42); (2) plaques, nodules, or tumors that arise on or are associated with plaques suggestive of late-stage MF (IIB and III of the TNM classification) (n = 16); (3) erythroderma (n = 50); and (4) nodules or tumors that arise in normal skin, suggestive of non-MF CTCL (n = 32).
When compared with histopathologic examination, the addition of clonality analysis increased the sensitivity of CTCL diagnosis in all groups of patients except those with cutaneous lesions suggestive of late-stage MF, because the diagnosis was made based on histopathologic analysis alone in 100% of these cases. The main increase in sensitivity of CTCL diagnosis was observed in patients with erythroderma: 62% with histopathologic analysis alone to 87% with the combination of both methods (P = .04). Diagnostic specificity of molecular assays decreased from 100% to 76% (P = .01) in patients with patch lesions and from 100% to 70% (P = .04) in patients with nodules that occurred in normal skin due to the detection of a T-cell clone in 6 patients with follicular mucinosis without a histologic pattern of MF and in 5 of 20 cases of T-cell pseudolymphoma (25%), respectively. In contrast, a T-cell clone was not detected in the 34 patients with erythroderma of inflammatory origin.
Polymerase chain reaction analysis of cutaneous T-cell clonality could be useful for the diagnosis of CTCL in patients who present with erythroderma.