Staging Accuracy in Mycosis Fungoides and Sézary Syndrome Using Integrated Positron Emission Tomography and Computed Tomography

Objectives To evaluate the usefulness of integrated positron emission tomography and computed tomography (PET/CT) in staging mycosis fungoides (MF) and Sezary syndrome and to correlate PET/CT data with histopathologic diagnosis of lymph nodes (LNs). Design A single-center, prospective cohort analysis. Setting Academic referral center for cutaneous lymphoma. Patients Thirteen patients with MF and SS at risk for secondary LN involvement. Interventions Patients were clinically evaluated based on general physical examination, total body skin examination, and laboratory screening. They underwent integrated PET/CT followed by excisional biopsy of LNs. Main Outcome Measures We used PET/CT to assess LN size and metabolic activity. Enlarged LNs were defined as axillary or inguinal LNs with a short axis 1.5 cm or larger; or cervical LN, with a short axis 1.0 cm or larger. We classified LN pathologic results according to National Cancer Institute (LN1-4) and World Health Organization (WHO 1-3) criteria. We quantified PET activity using standardized uptake value (SUV) and correlated with LN grade. Results Based on CT size criteria alone, only 5 patients had enlarged LNs, whereas PET revealed hypermetabolic LNs in all 13 patients. Six patients had LN1-3, and 7 had effacement of LN architecture by lymphoma cells (LN4). Of the 7 patients with LN4 nodes, 4 had SS, and 3 had tumorous MF. Two patients with LN4 nodes had inguinal LNs smaller than 1.5 cm and would have been assigned an N0 classification without the use of integrated PET/CT. Correlation of SUV with LN grade revealed that LN1-3 nodes were associated with a mean SUV of 2.7 (median SUV, 2.2; range, 2.0-4.7) and LN4 nodes were associated with a mean SUV of 5.4 (median SUV, 3.9; range, 2.1-11.8). Patients with large cell transformation had the highest SUVs. Conclusions For staging MF and SS, PET/CT was more sensitive in detecting LN involved by lymphoma compared with CT data alone and thus may provide more accurate staging and prognostic information. The intensity of PET activity correlated with histologic LN grade.