Stage IIIB includes: (T0, N1b, N1c, M0); (T1a/b-T2a, N1b/c or N2b, M0); (T2b/T3a, N1a-N2b, M0). T0: No evidence of primary tumor (e.g., unknown primary or completely regressed melanoma). Thickness: Not applicable. Ulceration status: Not applicable. T1a: Tumor measuring less than 0.8 mm in thickness. Ulceration status: Without ulceration. T1b: Tumor measuring less than 0.8 mm in thickness with ulceration, or 0.8-1.0 mm with or without ulceration. T2a: Tumor measuring more than 1.0 and equal to or less than 2.0 mm in thickness. Ulceration status: Without ulceration. T2b: Tumor measuring more than 1.0 and equal to or less than 2.0 mm in thickness. Ulceration status: With ulceration. T3a: Tumor measuring more than 2.0 and equal to or less than 4.0 mm in thickness. Ulceration status: Without ulceration. N1b: One clinically detected nodal metastasis. Presence of in-transit, satellite, and/or microsatellite metastases: No. N1c: No regional lymph node disease. Presence of in-transit, satellite, and/or microsatellite metastases: Yes. N2b: Two or three nodal metastases at least one of which was clinically detected. Presence of in-transit, satellite, and/or microsatellite metastases: No. N1a: One clinically occult nodal metastasis (i.e., detected by sentinel lymph node biopsy). Presence of in-transit, satellite, and/or microsatellite metastases: No. N2a: Two or three clinically occult nodal metastases (i.e., detected by sentinel lymph node biopsy). Presence of in-transit, satellite, and/or microsatellite metastases: No. M0: No evidence of distant metastasis. LDH level is not applicable. (AJCC 8th ed.) [from NCI]