Abstract
Mitotic rate is no longer considered a staging criterion for thin melanoma in the 8th edition of the American Joint Committee on Cancer Staging Manual. The aim of this observational study was to identify prognostic factors for thin melanoma and predictors and prognostic significance of sentinel lymph node (SLN) involvement in a large multicenter cohort of patients with melanoma from nine tertiary care hospitals. A total of 4249 consecutive patients with thin melanoma diagnosed from January 1, 1998 to December 31, 2016 were included. The main outcomes were disease‐free interval and melanoma‐specific survival for the overall population and predictors of SLN metastasis (n = 1083). Associations between survival and SLN status and different clinical and pathologic variables (sex, age, tumor location, mitosis, ulceration, regression, lymphovascular invasion, histologic subtype, Clark level, and Breslow thickness) were analyzed by Cox proportional hazards regression and logistic regression. SLN status was the most important prognostic factor for melanoma‐specific survival (hazard ratio, 13.8; 95% CI, 6.1‐31.2; P < 0.001), followed by sex, ulceration, and Clark level for patients who underwent SLNB. A mitotic rate of >2 mitoses/mm2 was the only factor associated with a positive SLN biopsy (odds ratio, 2.9; 95% CI, 1.22‐7; P = 0.01. SLN status is the most important prognostic factor in thin melanoma. A high mitotic rate is associated with metastatic SLN involvement. SLN biopsy should be discussed and recommended in patients with thin melanoma and a high mitotic rate.
Highlights
Thin melanomas measuring 1 mm or less account for approximately 50% of all melanomas diagnosed in our area.[1]
Patients diagnosed after January 1, 1998 were included. Those treated before this date were intentionally omitted, as most of the hospitals did not start performing sentinel lymph node biopsy (SLNB) in patients considered at risk for regional lymphatic metastasis until 1998.3 All the databases complied with the relevant laws
This study shows that SLN status is the most important prognostic factor in thin melanoma
Summary
Thin melanomas measuring 1 mm or less account for approximately 50% of all melanomas diagnosed in our area.[1]. The only two updated clinical practice guidelines—version 1.2018 of the National Comprehensive Cancer Network (NCCN) guidelines (version 1.2018)[8] and the American Society of Clinical Oncology‐Society of Surgical Oncology (ASCO‐SSO) guideline9—recommend discussing and considering SLNB in patients with T1b melanoma (ulcerated tumors or tumors with a Breslow thickness ≥0.8 mm). The NCCN guidelines recommend considering SLNB in patients with T1a melanoma (tumors
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