Subcutaneous Panniculitis-Like T-Cell Lymphoma With Granulomas as the Predominant Feature

Area of Science:

• Dermatopathology
• Hematopathology
• Oncology

Background:

• Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare cutaneous lymphoma affecting subcutaneous adipose tissue.
• SPTCL typically involves cytotoxic T cells but can rarely feature granulomas.
• Granulomatous inflammation is a common finding in various panniculitides, complicating SPTCL diagnosis.

Observation:

• We report a unique case of SPTCL where granulomas constituted the predominant inflammatory infiltrate (75%-80%).
• Differential diagnoses initially included infectious and autoimmune etiologies.

Findings:

• Immunohistochemistry revealed a CD3+, CD8+, TIA-1+, TCR beta+, CD4+ infiltrate with a high Ki67 proliferation index (~30%).
• TCR gene rearrangement studies were crucial to rule out autoimmune conditions like lupus panniculitis.
• This presentation is exceptionally rare, with only one prior reported case.

Implications:

• Dermatopathologists must consider SPTCL in the differential diagnosis of granulomatous panniculitis.
• Recognizing this granulomatous variant is essential for accurate diagnosis and appropriate patient management.
• This finding expands the spectrum of SPTCL presentations and diagnostic considerations.