Staging

The diagnosis, staging, and treatment of primary melanoma are intimately related. Melanoma is staged by the characteristics of the primary tumor, nodes, and metastases (TNM). The TNM system for melanoma staging correlates with prognosis (Table 1) (7). Primary

TABLE 1 AJCC Staging for Melanoma and Corresponding Survival

Stage

TNM

Depth (mm)

Ulceration

No. of +LN

Metastasis

5 yr survival (%)

10 yr survival (%)

0

Tis

In situ

No

0

0

99.7

99.2

IA

TlaNOMO

<1.0

No

0

0

95

88

IB

TlbNOMO

<1.0

Yes, >level IV

0

0

91

83

T2aN0M0

1.01-2.0

No

0

0

89

79

IIA

T2bN0M0

1.01-2.0

Yes

0

0

77

64

T3aN0M0

2.01-4.0

No

0

0

79

64

IIB

T3bN0M0

2.01-4.0

Yes

0

0

63

51

T4aN0M0

>4.01

No

0

0

67

54

NC

T4bN0M0

>4.01

Yes

0

0

45

32

INA

T1-4aN1aM0

Any

No

1

0

70

63

T1-4aN2aM0

Any

No

2-3

0

63

57

NIB

T1-4bN1aM0

Any

Yes

1

0

53

38

T1-4bN2aM0

Any

Yes

2-3

0

50

36

T1-4aN1bM0

Any

No

1

0

59

48

T1-4aN2bM0

Any

No

2-3

0

46

39

NIC

T1-4bN1bM0

Any

Yes

1

0

29

24

T1-4bN2bM0

Any

Yes

2-3

0

24

15

any TN3M0

Any

Any

4

0

27

18

IV

any TanyNMIa

Any

Any

Any

Distant skin, SC, LN

19

16

any TanyNMIb

Any

Any

Any

Lung

7

3

any TanyNMIc

Any

Any

Any

Any, increased LDH

10

6

Abbreviations: AJCC. American Joint Committee on Cancer; TNM, primary tumor, nodes, and metastases; LN, lymph node; SC, subcutaneous; LDH, lactate dehydrogenase. Source: From Refs. 8, 9.

Abbreviations: AJCC. American Joint Committee on Cancer; TNM, primary tumor, nodes, and metastases; LN, lymph node; SC, subcutaneous; LDH, lactate dehydrogenase. Source: From Refs. 8, 9.

to melanoma is staged chiefly by histopathology or microstage, defined as depth of invasion and measured in millimeters. This is referred to as Breslow thickness, after the pathologist who developed this method. Thin melanomas (< 1 mm) have less likelihood of metastatic spread, whereas thick melanomas (>4 mm) have a much higher metastasis rate.

Depth of invasion can also be measured by Clark's levels of invasion (7). This system relies on the pathological level of invasion from dermis to subcutaneous fat. Clark's level I extends through the epidermis but not into the basal lamina. Level II melanoma has entered the basal lamina. Melanoma extending through the papillary dermis is level III. Level IV tumors enter the reticular dermis and level V tumors reach the subcutaneous fat. Because of the challenge of distinguishing the various pathological levels, Clark's level of penetration is used less frequently than Breslow thickness. However, on body parts with overall thicker or thinner skin (i.e., ear and nose), Clark's levels can be more accurate than Breslow thickness. In general, melanoma of Clark's levels IV and V has a higher likelihood of metastatic spread.

In addition to depth of invasion, other important features of the primary melanoma are signs of regression and ulceration (7). Primary melanomas can elicit an immune response, resulting in tumor regression. Regression is seen pathologically by signs of fibrosis and pigment-containing macrophages in the upper dermis. Because the tumor may have been sufficiently deep to allow regional nodal metastasis prior to regression, signs of regression of the primary may prompt sentinel node biopsy (SNB) and closer followup. Ulcerated melanomas tend to be of the nodular histological type and behave more aggressively. Patients with ulcerated primaries have a decreased survival when compared with those with nonulcerated melanomas. Ulceration results in a tumor stage that is more advanced (Table 1).

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