Abstract: Subcutaneous panniculitis-like T-cell lymphoma and gamma/delta T-cell lymphoma involving fat are unique among the hematologic dyscrasias because of their almost exclusive involvement of the subcutaneous fat with little tendency toward extracutaneous dissemination. The systemic manifestations associated with this lymphoma are largely the sequelae of cytokine production by neoplastic T cells found within the subcutaneous fat. We hypothesized that the basis of this localization could be due to an interactive microenvironment between the neoplastic cells and the adipocytes. Given the expression of CCR5 in adipocytes, we explored the expression of its ligand CCL5 in the subcutaneous infiltrates in subcutaneous panniculitis-like T-cell lymphoma, gamma/delta T-cell lymphoma and compared it with those in lupus erythematosus profundus (LEP). We found that CCL5 was expressed in a significantly higher percentage of lymphocytes in lymphomas compared with those in LEP (P < 0.01). Additionally, the upregulation of CCL5 in areas of necrosis involved by lymphoma contrasted with the minimal staining in the zones of degeneration/necrosis in the setting of LEP. We observed direct internalization of CCL5-positive lymphocytes within adipocytes based on ultrastructural studies. This study shows that the basis of the adipocyte tropism may reflect a unique interaction between CCL5-positive lymphocytes and CCR5 positive adipocytes. Given the known pharmacologic inhibitors of CCR5-expression one might propose that using such inhibitors (ie, anti-CCR5) could be of therapeutic value in select cases.