TNM Staging of Salivary Gland Cancers

Once a person is diagnosed with cancer, the next step before deciding on treatment options is a determination of the stage of the cancer. Staging of salivary gland cancers is an important step in evaluating prognosis and treatment options.  It helps determining how much is the cancer volume in the body, how serious the cancer is and how best to treat it and what is the survival chance of patient.

The most commonly followed staging system through out the world is the TNM (Tumor, Node, Metastasis) staging as per the 8th edition of the American Joint Committee on Cancer (AJCC) Staging Manual, Head and Neck Section.

This staging of salivary gland cancers is practiced for malignant tumors of the major salivary glands (parotid, submandibular, and sublingual glands). In contrast, tumors arising from minor salivary glands are staged according to their site of origin.

T The T refers to the size and extent of the main tumor
N The N refers to the number of nearby lymph nodes that have cancer.
M Status of cancer spread to parts of the body outside of the head and neck

Clinical staging (cTNM) is determined on physical exam, imaging studies, laboratory work and biopsies. Classification of clinical stage is described using the lower case prefix c (e.g. cT, cN, cM).

Pathologic staging (pTNM) provides more data. This is possible only in surgically removed tumor specimens.

T Staging

Based on the clinical examination, salivary gland tumors are staged as follows

Primary tumor (T)
T category Clinical T criteria Pathological T criteria
TX Primary tumor cannot be assessed
T0 No evidence of primary tumor
Tis Carcinoma in situ
T1 Tumor 2 cm or smaller in greatest dimension without extraparenchymal extension*
T2 Tumor larger than 2 cm but not larger than 4 cm in greatest dimension without extraparenchymal extension*
T3 Tumor larger than 4 cm and/or tumor having extraparenchymal extension*
T4 Moderately advanced or very advanced disease
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.
* Extraparenchymal extension is clinical or macroscopic evidence of invasion of soft tissues. Microscopic evidence alone does not constitute extraparenchymal extension for classification purposes.

N Staging

N Staging refers to the spread of tumor to neck lymph nodes. Compared to AJCC 7th edition, the 8th edition has major change with inclusion of extranodal extension.

N category Clinical criteria Pathological Criteria
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in a single ipsilateral lymph node, 3 cm or smaller in greatest dimension and ENE(–)
N2 N2a Metastasis in a single ipsilateral node larger than 3 cm but not larger than 6 cm in greatest dimension and ENE(–) Metastasis in single ipsilateral node 3 cm or smaller in greatest dimension and ENE(+); or
A single ipsilateral node larger than 3 cm but not larger than 6 cm in greatest dimension and ENE(–)
N2b Metastases in multiple ipsilateral nodes, none larger than 6 cm in greatest dimension and ENE(–)
N2c Metastases in bilateral or contralateral lymph nodes, none larger than 6 cm in greatest dimension and ENE(–)
N3 N3a Metastasis in a lymph node larger than 6 cm in greatest dimension and ENE(–)
N3b Metastases in any node(s) with clinically overt ENE(+) Metastasis in a single ipsilateral node larger than 3 cm in greatest dimension and ENE(+); or
Multiple ipsilateral, contralateral, or bilateral nodes any with ENE(+); or
A single contralateral node of any size and ENE(+)
NOTE: A designation of “U” or “L” may be used for any N category to indicate metastasis above the lower border of the cricoid (U) or below the lower border of the cricoid (L). Similarly, clinical and pathological ENE should be recorded as ENE(–) or ENE(+).

M Staging

In TNM Classification of tumors, M Staging denotes distant metastasis. That is the spread of the tumor to another faraway location. The most common sites include lung, bone, liver, and distant lymph nodes.

M0 No distant metastasis
M1 Distant metastasis present

Prognostic Staging

Based on the above, TNM prognostic stage groups are defined as follows.

Stage Tis N0 M0
Stage I T1 N0 M0
Stage II T2 N0 M0
Stage III T3 N0 M0
T0 – 3 N1 M0
Stage IVA T4a N0-1 M0
T0 – 4a N2 M0
Stage IVB Any T N3 M0
T4b Any N M0
Stage IVC Any T Any N M1

The higher the stage of the disease, the worse is the prognosis.

References

  1. Gospodarowicz MK, Brierley JD, Wittekind C, editors. TNM classification of malignant tumours. John Wiley & Sons; 2017 Jan 17.
  2. Lydiatt WM, Patel SG, O’Sullivan B, Brandwein MS, Ridge JA, Migliacci JC, Loomis AM, Shah JP. Head and neck cancers—major changes in the American Joint Committee on cancer eighth edition cancer staging manual. CA: a cancer journal for clinicians. 2017 Mar 1;67(2):122-37.

Meet the author

Dr Sanu P Moideen is an Indian-born oto-rhino-laryngologist (ENT) based in Cochin, Kerala, India. He is currently working as Post-Doctoral Fellow in Head and Neck Oncology at Regional Cancer Center, Trivandrum, Kerala.

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