Evaluation Using a Combination of Lymphatic Invasion on D2‐40 Immunostain and Depth of Dermal Invasion is a Strong Predictor for Nodal Metastasis in Extramammary Paget's Disease

In extramammary Paget's disease (EPD), lymph node metastasis occasionally occurs and nodal metastasis influences prognosis. Therefore, in the present study a predictor of nodal metastasis in EPD was examined. Surgical specimens from 54 cases of EPD in the external genitalia were examined on D2-40 immunostain. In 23 cases, dissection of the inguinal lymph nodes was performed. Dermal invasion occurred in 24 patients (44.4%). Nodal metastasis was found in seven patients who had dermal invasion > 1 mm. In non-metastatic patients, three had dermal invasion < 0.5 mm in depth. Lymphatic invasion was well detected on D2-40 immunostain, and invasion was found in five patients. All four patients with lymphatic invasion, in whom lymph node dissection was performed, had nodal metastasis. However, three patients with dermal invasion, who did not have lymphatic invasion, did have nodal metastasis, and the depth of invasion was > 1 mm. Dermal invasion (P < 0.001) and lymphatic invasion according to D2-40 immunostain (P = 0.001) had a positive correlation with nodal metastasis. In conclusion, evaluation using a combination of lymphatic invasion according to D2-40 immunostain and depth of dermal invasion is a strong predictor of nodal metastasis in EPD.