Background: Breslow thickness is an important prognostic factor in malignant melanoma. Thick (>4mm) melanoma without nodal metastasis was classified as stage III in AJCC 5th edition and then revised as stage II in AJCC 6th and 7th edition because of anatomic compartmentalization. Tumor thickness greater than 4 mm was common in acral lentiginous melanoma in Taiwan. The prognosis of these “superthick” melanoma in Asia have not been widely discussed. Here we exam the prognosis of tumor thickness beyond 4-mm.
Materials and Methods: We retrospectively reviewed our databank of non-metastatic melanoma between 2001 and 2010 at Chang Gung Memorial Hospital, Linkuo. A total of 209 patients with non-metastatic melanoma were identified. The second cohort with 181 patients, registered in 1990-2000, was combined into analysis later to verify our findings. Data was collected from primary chart review.
Results: The median overall survival (mOS) of node-negative melanoma was better than node-positive melanoma (p=0.064). However, a significantly shorter OS was identified in T4N0 group, compared with T1-3N1 group. (p=0.02) We suggested that a subgroup of T4N0 had a worse outcome and might be classified as stage III, instead of stage IIC in AJCC 7th tumor staging. When 15mm in thickness as the cut-off value, the median OS of thickness >15mm is significantly worse than thickness ≤15mm in T4N0M0 group. (p=0.025) The median OS of T4(>15mm)N0M0 group is significantly worse then T1-3N1M0 group. (p=0.011) When the two cohorts (registered in 1990-2000 and in 2001-2010) were combined into analysis, the median OS of T4N0 (>15mm) was still significantly worse than T4N0 (≤15mm).
Conclusions: A subgroup of thick melanoma, with thickness greater than 15mm and no nodal metastasis, should be classified as stage III. Further validation in a larger cohort followed by amendment of melanoma staging in Asia is necessary.