CARCINOMA OF SKIN OF THE HEAD AND NECK (ICD‐O‐3 C44.0, C44.2–4)

Rules for Classification

The classification applies only to carcinomas, excluding Merkel cell carcinoma. There should be histological confirmation of the disease and division of cases by histological type.

Anatomical Sites and Subsites

The following sites are identified by ICD‐O‐3 topography rubrics (see Fig. 334):

Lip (excluding vermilion surface) (C44.0)
External ear (C44.2)
Other and unspecified parts of face (C44.3)
Scalp and neck (C44.4)

Schematic illustration of ICD-O topography rubrics, Lip, External ear, Other and unspecified parts of face, Scalp and neck. — **Fig. 334**

Regional Lymph Nodes

The regional lymph nodes are Ipsilateral preauricular, submandibular, cervical and supraclavicular lymph nodes (see Fig. 335).

TNM Clinical Classification

T – Primary Tumour

Tx	Primary tumour cannot be assessed
T0	No evidence of primary tumour
Tis	Carcinoma in situ (Fig. 336)
T1	Tumour 2 cm or less in greatest dimension (Fig. 337)
T2	Tumour > 2 cm and ≤ 4 cm in greatest dimension (Fig. 338)
T3	Tumour > 4 cm in maximum dimension or minor bone erosion or perineural invasion or deep invasion* (Fig. 339)
T4a	Tumour with gross cortical bone/marrow invasion
T4b	Tumour with skull base or axial skeleton invasion including foraminal involvement and/or vertebral foramen involvement to the epidural space

Note
*In the case of multiple simultaneous tumours, the tumour with the highest T category is classified and the number of separate tumours is indicated in parentheses, e.g., T2(5) (Fig. 340)

Schematic illustration of Carcinoma in situ, Epithelium, Papillary dermis, Reticular dermis, Subcutaneous tissue. — **Fig. 336**

Schematic illustration of Tumor 2 cm or less in greatest dimension. — **Fig. 337**

Schematic illustration of Tumor greater than or equal to 2 cm and less than or equal to 4 cm in greatest dimension. — **Fig. 338**

Schematic illustration of Tumor greater than or equal to 4 cm in maximum dimension or minor bone erosion or perineural invasion or deep invasion. — **Fig. 339**

Schematic illustration of the tumour with the highest T category is classified and the number of separate tumours is indicated in parentheses. — **Fig. 340**

N – Regional Lymph Nodes

N0	No regional lymph node metastasis
N1	Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension without extranodal extension (Fig. 341)
N2	Metastasis as described below:
	N2a	Metastasis in a single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension without extranodal extension (Fig. 342)
	N2b	Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension, without extranodal extension (Fig. 343)
	N2c	Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension, without extranodal extension (Fig. 344)
N3a	Metastasis in a lymph node more than 6 cm in greatest dimension without extranodal extension (Fig. 345)
N3b	Metastasis in single or multiple lymph nodes with clinical extranodal extension

Note
*The presence of skin involvement or soft tissue invasion with deep fixation/tethering to underlying muscle or adjacent structures or clinical signs of nerve involvement is classified as clinical extranodal extension.

Schematic illustration of Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension without extranodal extension. — **Fig. 341**

Schematic illustration of Metastasis in a single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension without extranodal extension. — **Fig. 342**

Schematic illustration of Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension, without extranodal extension. — **Fig. 343**

Schematic illustration of Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension, without extranodal extension. — **Fig. 344**

Schematic illustration of Metastasis in a lymph node more than 6 cm in greatest dimension without extranodal extension. — **Fig. 345**

M – Distant Metastasis

M0	No distant metastasis
M1	Distant metastasis

pTNM Pathological Classification

The pT categories correspond to the T categories

pN – Regional Lymph Nodes

Histological examination of a selective neck dissection specimen will ordinarily include 10 or more lymph nodes. Histological examination of a radical or modified radical neck dissection specimen will ordinarily include 15 or more lymph nodes.

pNX	Regional lymph nodes cannot be assessed
pN0	No regional lymph node metastasis
pN1	Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension without extranodal extension
pN2	Metastasis as described below:
	pN2a	Metastasis in a single ipsilateral lymph node, less than 3 cm in greatest dimension with extranodal extension, or more than 3 cm but not more than 6 cm in greatest dimension without extranodal extension
	pN2b	Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension without extranodal extension
	pN2c	Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension without extranodal extension
pN3a	Metastasis in a lymph node more than 6 cm in greatest dimension without extranodal extension
pN3b	Metastasis in a lymph node more than 3 cm in greatest dimension with extranodal extension, or multiple ipsilateral, contralateral or bilateral, with extranodal extension