Indolent primary cutaneous gamma-delta T-cell lymphoma

Summary: Primary cutaneous gamma-delta T-cell lymphoma (PCGDTCL) is an extremely rare malignancy representing <1% of all skin lymphomas. PCGDTCL is defined by a clonal proliferation of mature activated γ/δ T cells and generally displays a rapid and aggressive clinical course with a median overall survival of 15 months. We present an unusual case of a 43-year-old female with a 7-month history of tender erythematous nodule located on the right upper extremity. Excisional biopsy revealed a panniculitic CD3+/TCRδ+/TIA1+/CD4subset/CD8subset/ CD5-/BF1- clonal lymphocytic infiltrate, leading to a diagnosis of PCGDTCL. There were no fevers, chills, weight loss, or adenopathy, and neither recurrence or new lesions have been reported. Very few cases of PCGDTCL with an initial and long-term indolent course have been published. This case highlights how PCGDTCL can exhibit an indolent course and should be considered when a patient presents with lobular lymphocytic panniculitis, even with minimal clinical symptoms, as this entity can mimic diseases with similar benign clinical behavior and histopathological presentation, such as lupus panniculitis and subcutaneous panniculitis-like-T-cell lymphoma. It is important to recognize that not all PCGDTCLs can have a poor prognosis; however, close monitoring for a shift to an aggressive form is essential.