Diagnostic value of TCRγ rearrangement analysis by PCR in early mycosis fungoides: A clinicopathologic study

Abstract

Background: Mycosis fungoides (MF) is the most common type of primary cutaneous T-cell lymphoma. Diagnosing early-stage MF remains challenging because its clinical and histopathological features frequently mimic benign inflammatory dermatoses. Molecular analysis of T-cell receptor (TCR) gene rearrangements has emerged as a valuable adjunctive tool in this context. The objective of this study was to evaluate the diagnostic value of polymerase chain reaction (PCR) detection of TCR gamma (TCRγ) gene rearrangements in patients with suspected early MF, and to determine its utility within an integrated clinicopathological approach.

Methods: This retrospective study included 16 patients who underwent skin biopsy for lesions suspicious for MF between 2019 and 2021 at the Farhat Hached University Hospital, Sousse. Clinical data, histopathological findings, immunohistochemical profiles, and molecular analyses were reviewed. T-cell clonality was assessed via PCR amplification of TCRγ gene rearrangements using formalin-fixed paraffin-embedded tissue.

Results: The study population comprised 16 patients aged 4 to 73 years (mean age: 43.5 years). Histopathological examination revealed superficial lymphoid infiltrates with varying degrees of epidermotropism, which were suggestive of but not definitive for MF. Immunohistochemical analysis showed a predominance of CD3-positive T lymphocytes with CD4 predominance in most cases. PCR analysis detected clonal TCRγ rearrangements in 8 cases (50%), polyclonal patterns in 7 cases, and an oligoclonal pattern in 1 case. After integrating clinical, histological, immunophenotypic, and molecular findings, the final diagnosis was MF in 13 patients and chronic inflammatory dermatosis in 3 patients.

Conclusion: PCR detection of TCRγ gene rearrangements represents a valuable ancillary technique in the diagnostic evaluation of suspected early MF. However, molecular results must always be interpreted in conjunction with clinical, histological, and immunophenotypic findings to avoid diagnostic pitfalls.