Staging and Assessment of Lymph Node Involvement by18F-Fluorodeoxyglucose-Positron Emission Tomography in Invasive Extramammary Paget's Disease

BACKGROUND: 18F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET) is a functional and metabolic imaging modality that is efficacious in nodal staging and detection of extranodal involvement for malignant tumors. OBJECTIVE: We describe the novel use of PET for staging patients with invasive extramammary Paget's disease (EMPD) and discuss the potential advantages of this technology relative to other diagnostic modalities. METHODS: We evaluated three patients with invasive EMPD whose staging was made by PET at Hokkaido University Hospital. RESULTS: All lymph nodes detected by PET were over 10 mm. Distant internal metastases were not seen in all cases. PET failed to detect 10 and 5 to 7 mm nodal involvement but succeeded in detecting nodes over 10 mm. CONCLUSIONS: These data suggest that PET may be useful in determining disease activity at the time of initial diagnosis but is less useful and proves difficult to detect a small or subclinical involvement. This is the first report of PET being used for invasive EMPD.