Staging and Assessment of Lymph Node Involvement by18F-Fluorodeoxyglucose–Positron Emission Tomography in Invasive Extramammary Pagetʼs 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.