DR P MARAZZI / SCIENCE PHOTO LIBRARY Diagnosis of Cutaneous T-cell Lymphomas Skin biopsy Peripheral blood smear and flow cytometry for circulating malignant T-cells (Sézary cells) For staging, lymph node biopsy and CT of chest, abdomen, and pelvis or FDG-PET (fluorodeoxyglucose-positron emission tomography) Diagnosis is based on skin biopsy, but histology may be equivocal early in the course because of insufficient quantities of lymphoma cells.