Salivary gland tumor staging

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]

Overview

According to the TNM staging system by the American Joint Committee on Cancer, there are four stages of salivary gland cancers based on the tumor size, lymph nodes involved, and metastasis.

Staging

• The American Joint Committee on Cancer (AJCC) has designated staging by TNM classification to define salivary gland cancer. In general, tumors of the major salivary glands are staged according to size, extraparenchymal extension, lymph node involvement (in parotid tumors, whether or not the facial nerve is involved), and presence of metastases.
• Tumors arising in the minor salivary glands are staged according to the anatomic site of origin (e.g., oral cavity and sinuses). Clinical stage, particularly tumor size, may be the critical factor to determine the outcome of salivary gland cancer and may be more important than histologic grade. Diagnostic imaging studies may be used in staging. With excellent spatial resolution and superior soft tissue contrast, magnetic resonance imaging (MRI) offers advantages over computed tomographic scanning in the detection and localization of head and neck tumors. Overall, MRI is the preferred modality for evaluation of suspected neoplasms of the salivary glands.

Primary tumor (T)

T Classification	Thickness
TX	Primary tumor cannot be assessed
T0	No evidence of a primary tumor
T1	Tumor ≤2 cm in greatest dimension without extraparenchymal extension
T2	Tumor >2 cm but ≤4 cm in greatest dimension without extraparenchymal extension b
T3	Tumor >4 cm and/or tumor having extraparenchymal extension b
T4a	Moderately advanced disease. Tumor invades skin, mandible, ear canal, and/or facial nerve
T4b	Very advanced disease Tumor invades skull base and/or pterygoid plates and/or encases carotid artery

b Extraparenchymal extension is clinical or macroscopic evidence of invasion of soft tissues. Microscopic evidence alone does not constitute extraparenchymal extension for classification purposes.

Regional Lymph Nodes (N)

N classification	Nodal Mass
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Metastasis in a single ipsilateral lymph node, ≤3 cm in greatest dimension
N2	Metastasis in a single ipsilateral lymph node, >3 cm but ≤6 cm in greatest dimension Metastases in multiple ipsilateral lymph nodes, ≤6 cm in greatest dimension Metastases in bilateral or contralateral lymph nodes, ≤6 cm in greatest dimension
N2a	Metastasis in a single ipsilateral lymph node, >3 cm but ≤6 cm in greatest dimension
N2b	Metastases in multiple ipsilateral lymph nodes, ≤6 cm in greatest dimension
N2c	Metastases in bilateral or contralateral lymph nodes, ≤6 cm in greatest dimension
N3	Metastases in bilateral or contralateral lymph nodes, ≤6 cm in greatest dimension

Distant Metastasis (M)

N classification	Nodal Mass
M0	No distant metastasis
M1	Distant metastasis

Anatomic Stage/Prognostic Groups

Stage	T	N	M
Stage 1	T1	N0	M0
Stage II	T2	N0	M0
Stage III	T3 T1 T2 T3	N0 N1 N1 N1	M0 M0 M0 M0
Stage IVA	T4a T4a T1 T2 T3 T4a	N0 N1 N2 N2 N2 N2	M0 M0 M0 M0 M0 M0
Stage IVB	T4b Any T	Any N N3	M0 M0
Stage IVC	Any T	Any N	M1

Tumor grades of salivary gland cancer

• Grading is a way of classifying salivary cancer cells based on their appearance and behavior when viewed under a microscope. To find out the grade of a tumor, the biopsy sample is examined under a microscope. A grade is given based on how the cancer cells look and behave compared with normal cells (differentiation). This can give the healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread. The grade of salivary gland cancer is based on the degree of differentiation of cells and their rate of growth.

Grade	Description
low	Well differentiated – slow growing, less likely to spread
Intermediate	Moderately well-differentiated
High	poorly differentiated – tend to grow quickly, more likely to spread

• Grading for salivary gland cancers is used mainly for mucoepidermoid carcinomas, adenocarcinomas, adenocarcinoma NOS, squamous cell carcinomas and adenoid cystic carcinomas. Other salivary gland cancers can also be graded in the same way. Grading plays an important part in planning salivary gland cancer treatment and can also be used to help estimate the prognosis. However, the grade is not the only factor used to predict the future outcome.
• It must be considered together with staging information. Staging, in particular tumor size, is an important prognostic factor and may be more important than the grade in terms of successful treatment. For example, sometimes a stage I, intermediate or high-grade tumor can be treated with more success than a low-grade tumor that is a stage III.

Low grade	Low, intermediate or high grade	High grade
Acinic cell carcinoma	Adenocarcinoma not otherwise specified (NOS)	Adenoid cystic carcinoma*
Basal cell adenocarcinoma	Mucoepidermoid carcinoma	Anaplastic small cell carcinoma
Clear cell carcinoma	Squamous cell carcinoma	Carcinosarcoma
Cystadenocarcinoma		Small and large cell undifferentiated carcinoma
Epithelia-myoepithelial carcinoma		Salivary duct carcinoma
Mucinous adenocarcinoma		Carcinoma ex pleomorphic adenoma
Polymorphous low-grade adenocarcinoma (PLGA)

• *Some adenoid cystic carcinomas can also be intermediate grade.