Predictors of Dermal Invasion and Sentinel Lymph Node Metastasis in Patients With Extramammary Paget's Disease Without Clinical Lymph Node Enlargement

Sentinel lymph node biopsy (SLNB) has prognostic value in extramammary Paget's disease (EMPD) without lymph node enlargement; however, its therapeutic value is unknown. The likelihood of sentinel lymph node metastasis is extremely low, especially when the primary tumor is an intraepidermal lesion; therefore, sentinel node biopsy should not be performed in such cases. To avoid excessive sentinel node biopsy in patients with EMPD, we investigated the preoperative biomarkers that predict the degree of invasiveness of the primary tumor and sentinel lymph node metastasis. We reviewed 121 patients who underwent primary resection and SLNB. The invasion level of the primary tumor was intraepidermal in 50 patients (41.3%), microinvasion into the papillary dermis in 34 (28.1%), and deep invasion into/beyond the reticular dermis in 37 (30.6%). The sentinel node metastasis was positive in 0%, 5.9%, and 62.2% of patients in the intraepidermal, microinvasion, and deep invasion groups, respectively. Presence of nodules (odds ratio: 6.820, p = 0.001) and neutrophil-to-lymphocyte ratio (NLR) (≥ 3.03, odds ratio: 4.260, p = 0.009) were identified as independent predictive factors for deep dermal invasion of the primary tumor and sentinel node metastasis (with nodules, odds ratio: 8.460, p < 0.001 and NLR ≥ 2.87, odds ratio: 3.870, p = 0.016). The metastasis-positive group had a significantly lower overall survival than the negative group (median overall survival: 27.6 months vs. not reached, log-rank test, p < 0.001). In conclusion, routine SLNB may be useful for predicting the prognosis of patients with EMPD without clinical lymph node enlargement. However, the likelihood of sentinel lymph node metastasis is extremely low in intraepidermal and microinvasive primary lesions. It may be reasonable to proactively recommend SLNB, particularly in cases with confirmed deep invasion lesions, the presence of nodules, or elevated NLR.