Usefulness of sentinel lymph node biopsy for the detection of metastasis in the early stage of extramammary Paget's disease.

BACKGROUND: Invasive cases of extramammary Paget's disease have a poor prognosis, owing to its rapid progression and resistance to irradiation and chemotherapy. Morton et al. introduced a technique to identify sentinel lymph nodes by local injection of vital dyes and reported its benefit for managing the progress of malignant melanoma.

OBJECTIVES: Since the rate of lymph node metastasis of extramammary Paget's disease is not uncommon (reported from 8.5% to 26%), this study tested the hypothesis that sentinel lymph node biopsy would be useful to detect lymph node metastasis in the clinically early stage of extramammary Paget's disease.

MATERIALS & METHODS: Eighteen patients with primary extramammary Paget's disease were enrolled in the study. The precise location of sentinel lymph nodes was visualized using either intraoperative patent blue dye injection or indocyanine green dye injection in combination with a hand-held gamma-detecting probe after a 99mTc phytate injection.

RESULTS: Of the 18 patients, sentinel lymph node metastasis was identified in 2 (Cases 2 and 15) of the 2 patients with deep invasion and in 1 (Case 12) of the 7 patients with minimal dermal invasion, however, it was absent in 9 patients who had been categorized into the intraepidermal group.

CONCLUSION: This study demonstrates that extramammary Paget's disease possibly causes metastasis via regional lymphatic systems to which the lesion belongs, even in the early stages of no nodule or tumor formation, and that sentinel lymph node biopsy is useful to detect lymph node metastasis.