Definitions of categories
Here you can look up what the M, N, and T categories mean.
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Definition of Distant Metastasis (M)1
M0
| Anatomic site | No evidence of distant metastasis |
| LDH level | Not applicable |
M1a
| Anatomic site | Distant metastasis to skin, soft tissue including muscle, and/or nonregional lymph node |
| LDH level | Not recorded or unspecified |
M1a(0)
| Anatomic site | Distant metastasis to skin, soft tissue including muscle, and/or nonregional lymph node |
| LDH level | Not elevated |
M1a(1)
| Anatomic site | Distant metastasis to skin, soft tissue including muscle, and/or nonregional lymph node |
| LDH level | Elevated |
M1b
| Anatomic site | Distant metastasis to lung with or without M1a sites of disease |
| LDH level | Not recorded or specified |
M1b(0)
| Anatomic site | Distant metastasis to lung with or without M1a sites of disease |
| LDH level | Not elevated |
M1b(1)
| Anatomic site | Distant metastasis to lung with or without M1a sites of disease |
| LDH level | Elevated |
M1c
| Anatomic site | Distant metastasis to non-CNS visceral sites with or without M1a or M1b sites of disease |
| LDH level | Not recorded or unspecified |
M1c(0)
| Anatomic site | Distant metastasis to non-CNS visceral sites with or without M1a or M1b sites of disease |
| LDH level | Not elevated |
M1c(1)
| Anatomic site | Distant metastasis to non-CNS visceral sites with or without M1a or M1b sites of disease |
| LDH level | Elevated |
M1d
| Anatomic site | Distant metastasis to CNS with or without M1a, M1b, or M1c sites of disease |
| LDH level | Not recorded or unspecified |
M1d(0)
| Anatomic site | Distant metastasis to CNS with or without M1a, M1b, or M1c sites of disease |
| LDH level | Not elevated |
M1d(1)
| Anatomic site | Distant metastasis to CNS with or without M1a, M1b, or M1c sites of disease |
| LDH level | Elevated |
Definition of Regional Lymph Node (N)1
NX
| Number of metastatic nodes | Regional nodes not assessed |
| In transit, satellite, and/or microsatellite metastases | No |
N0
| Number of metastatic nodes | No regional metastases detected |
| In transit, satellite, and/or microsatellite metastases | No |
N1
| Number of metastatic nodes | 1 |
| In transit, satellite, and/or microsatellite metastases | --- |
N1a
| Number of metastatic nodes | 1 clinically occult |
| In transit, satellite, and/or microsatellite metastases | No |
N1b
| Number of metastatic nodes | 1 clinically detected |
| In transit, satellite, and/or microsatellite metastases | No |
N1c
| Number of metastatic nodes | No regional lymph node disease |
| In transit, satellite, and/or microsatellite metastases | Yes |
N2
| Number of metastatic nodes | 2 or 3 |
| In transit, satellite, and/or microsatellite metastases | --- |
N2a
| Number of metastatic nodes | 2 or 3 clinically occult |
| In transit, satellite, and/or microsatellite metastases | No |
N2b
| Number of metastatic nodes | 2 or 3, at least one of which was clinically detected |
| In transit, satellite, and/or microsatellite metastases | No |
N2c
| Number of metastatic nodes | 1 clinically occult or detected |
| In transit, satellite, and/or microsatellite metastases | Yes |
N3
| Number of metastatic nodes | 4 or more |
| In transit, satellite, and/or microsatellite metastases | --- |
N3a
| Number of metastatic nodes | 4 or more clinically occult |
| In transit, satellite, and/or microsatellite metastases | No |
N3b
| Number of metastatic nodes | 4 or more, at least one of which was clinically detected, or presence of any number of matted nodes |
| In transit, satellite, and/or microsatellite metastases | No |
N3c
| Number of metastatic nodes | 2 or more clinically detected and/or presence of any matted nodes |
| In transit, satellite, and/or microsatellite metastases | Yes |
Definition of
Primary Tumor
(T)1
TX
(Primary tumor thickness cannot be assessed)
| Thickness | Not applicable |
| Ulceration status | Not applicable |
T0
(No evicence of primary tumor)
| Thickness | Not applicable |
| Ulceration status | Not applicable |
Tis
(Melanoma in situ)
| Thickness | Not applicable |
| Ulceration status | Not applicable |
T1
| Thickness | = 1.0 mm |
| Ulceration status | Unknown or unspecified |
T1a
| Thickness | < 0.8 mm |
| Ulceration status | Without ulceration |
T1b
| Thickness | < 0.8 mm | 0.8 - 1.0 mm |
| Ulceration status | With ulceration | With or without ulceration |
T2
| Thickness | > 1.0 - 2.0 mm |
| Ulceration status | Unknown or specified |
T2a
| Thickness | > 1.0 - 2.0 mm |
| Ulceration status | Without ulceration |
T2b
| Thickness | > 1.0 - 2.0 mm |
| Ulceration status | With ulceration |
T3
| Thickness | > 2.0 - 4.0 mm |
| Ulceration status | Unknown or unspecified |
T3a
| Thickness | > 2.0 - 4.0 mm |
| Ulceration status | Without ulceration |
T3b
| Thickness | > 2.0 - 4.0 mm |
| Ulceration status | With ulceration |
T4
| Thickness | > 4.0 mm |
| Ulceration status | Unknown or unspecified |
T4a
| Thickness | > 4.0 mm |
| Ulceration status | Without ulceration |
T4b
| Thickness | > 4.0 mm |
| Ulceration status | With ulceration |