Post-transplant CD4+ non-cytotoxic γδ T cell lymphoma with lymph node involvement

Gamma delta T cells represent a minor subset of the normal lymphocyte component of the human immune system, largely inhabiting mucosal surfaces. Gamma delta T cell lymphomas (γδ TCLs) are thought to be derived from these cells and are rare, extremely aggressive lymphomas that typically exhibit a cytotoxic phenotype and often present in extranodal sites, most commonly as cutaneous or hepatosplenic subtypes. The immunophenotype usually lacks both CD4 and CD8 expression, but occasional cases express CD8. CD4 expression in γδ TCLs is exceedingly rare. The few reported cases tend to show a non-cytotoxic phenotype with preferential involvement of the lymph nodes. Cases showing cutaneous presentation or with an immunosuppressive clinical history, while relatively common among typical γδ TCLs, are even rarer among this unusual CD4+ subset. While this very small group appears to have an equally dismal prognosis to other types of γδ TCL, little else is known as to how they may differ biologically and whether they should be treated as a separate entity. We report a unique case of CD4-positive gamma delta T cell lymphoma with skin and systemic lymph node involvement in the post-transplant setting.