Subcutaneous Panniculitis-Like T-Cell Lymphoma With Increased γδ T Cells: A Potential Diagnostic Pitfall

Area of Science:

• Dermatology
• Hematology
• Oncology

Background:

• Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare cutaneous lymphoma.
• SPTCL is characterized by CD8+ T cells with an alpha-beta (αβ) phenotype.
• Distinguishing SPTCL from aggressive lymphomas like primary cutaneous gamma-delta (γδ) T-cell lymphoma is vital for prognosis.

Purpose of the Study:

• To present a case of SPTCL with an unusual increase in γδ T cells.
• To highlight the diagnostic challenges posed by this finding.
• To emphasize the importance of clinicopathologic correlation in SPTCL diagnosis.

Main Methods:

• Case presentation of a 26-year-old woman with SPTCL.
• Histopathologic examination of biopsy specimens.
• Immunophenotypic analysis (CD3, CD4, CD8, CD7, TIA1, granzyme B, TCR βF1, CD30, EBV-encoded small RNA, TCR δ, CD123).
• Molecular analysis of TCR β and γ gene rearrangements.

Main Results:

• The patient presented with erythematous patches and hyperpigmented nodules.
• Biopsies showed atypical lymphoid infiltrate with adipotropism, predominantly CD8+ T cells.
• A significant increase in T cells expressing TCR δ was observed, some surrounding adipocytes.
• Molecular analysis confirmed monoclonal TCR β and γ gene rearrangements.
• Despite elevated γδ T cells (20%-50%), diagnosis of SPTCL was supported by overall findings.

Conclusions:

• Increased γδ T-cell populations can occur in SPTCL.
• This finding can lead to misdiagnosis as primary cutaneous γδ T-cell lymphoma.
• Thorough clinicopathologic correlation is essential for accurate SPTCL diagnosis and management.