Evolution of TNM Classification for Clinical Staging of Oral Cancer: The Past, Present and the Future

Abstract

Purpose

The AJCC (American Joint Committee on Cancer) Cancer Staging Manual, 1st Edition, was published in 1977 which focused on the TNM classification and staging of cancer to allow easy communication, formulation of a treatment plan and predict the prognosis, among the medical fraternity.

Methods

Ever since the beginning, various modifications of the classification were introduced and released by the joint collaboration of AJCC and UICC (International Union Against Cancer) in various editions of cancer staging manuals.

Results

The present review article was kept focused onto the changes introduced in the clinical staging of cancers of oral cavity. These changes came a long way since 1st edition 1944, to the eighth edition which was published in 2017.

Conclusions

This article is a critical review on the past and present perspectives of the TNM classification of the oral cavity that were addressed and changed, adding a light on the future trends or necessary inclusions that would formulate a much easily acceptable and useful classification system.

Introduction

Pierre Denoix proposed a staging system for solid tumours based on tumour characteristics (T), nodal spread (N), and distant metastasis (M) in 1944 [1]. The UICC (International Union Against Cancer) adopted this system in 1954. The AJCC (American Joint Committee on Cancer) was established in 1958 publishing separate definitions of TNM categories. The UICC and AJCC worked independently for nearly 25 years and had separate staging systems for classification of cancer. In 1987, the UICC and the AJCC TNM classifications were unified. The first edition of the AJCC/UICC TNM classification was published in 1977.

Since then, the TNM classification has been widely used for treatment planning and also to estimate the prognosis of the case [1]. Moreover, it helped the clinicians in evaluating and comparing the outcomes of the protocols employed in the treatment. The constant drive to incorporate modifications in the TNM classification is only to make it more convenient and user-friendly, also making it informative at the same time. However, once the classification is more informative, it becomes complex and might be haphazard or difficult to use. The aim of the current review is to provide an insight into the development, modifications and evolution of the TNM classification ever since the inception of the first edition of the Cancer Staging Manual in 1977. (Table 1).

Table 1.

First edition of AJCC-1977 [1]

Tumour (T)		Node (N)		Metastasis (M)
TX	No available information on primary tumour	NX	Nodes cannot be assessed	MX	Not assessed
TO	No evidence of primary tumour	NO	No clinically positive nodes	MO	No (known) distant metastasis
TIS	Carcinoma in situ	N1	Single clinically positive homolateral node less than 3 cm in diameter	MI	Distant metastasis present
TI	Greatest diameter of primary tumour less than 2 cm	N2	Single clinically positive homolateral node 3 to 6 cm in diameter or multiple clinically positive homolateral nodes, none over 6 cm in diameter
T2	Greatest diameter of primary tumour 2 to 4 cm	N2a	Single clinically positive homolateral node 3 to 6 cm in diameter
T3	Greatest diameter of primary tumour more than 4 cm
T4	Massive tumour greater than 4 cm in diameter with deep invasion to involve antrum, pterygoid muscles, root of tongue, or skin of neck	N2b	Multiple clinically positive homolateral nodes, none over 6 cm in diameter
		N3	Massive homolateral node(s), bilateral nodes, or contralateral node(s)
		N3a	Clinically positive homolateral node(s), none over 6 cm in diameter
		N3b	Bilateral clinically positive nodes (in this situation, each side of the neck should be staged separately; that is, N3b: right, N2a; left, N1)
		N3c	Contralateral clinically positive node(s) only

The first edition provided an elaborate, comprehensive and a detailed description of every aspect of the case, including the size of the tumour, nodal involvement and metastasis. It also provided information about the presence of residual tumour post the surgical treatment, stage grouping, histopathological grading and performance status of the host, also along with the graphical representation of survival on Karnofsky scale and Zubrod scale.

Though this is highly informative regarding the case, it might be a little difficult to use as it is lengthier and inclusive of many parameters. However, in spite of the drawbacks, most aspects of the same classification is currently under practice among the clinicians. (Table 2).

Table 2.

Inclusions in the second edition of AJCC-1983 [2]

Tumour (T)		Node (N)		Metastasis (M)
TX	Minimum requirements to assess the primary tumour cannot be met	NX	Minimum requirements to assess the lymph nodes cannot be met	MX	Minimum requirements to assess the presence of distant metastasis

Other aspects—similar to previous editions.

The “T” aspect of the TNM classification had a minor change in the second edition; the TX was modified as “minimum requirements to assess the primary tumour cannot be met” as of compared to that in the first edition which read “No available information on primary tumour”.

The “N” aspect also included NX which indicated “minimum requirements to assess the lymph nodes cannot be met” as compared to that in the first edition where NX stated “nodes cannot be assessed”.

The “M” aspect also included MX which indicated “minimum requirements to assess the presence of distant metastasis”. The rest of the aspects and denotations of t, n and m were similar to the first edition.

The second edition however included certain new elaborate aspects providing a much detailed description of the tumour, being as follows:

• Location of the tumour

• Characteristics of the tumour

• Involvement of the neighbouring region

Though this inclusion provided excellent information on the damage or the extent of the lesion and its severity, it again made the classification lengthy. However, it was vivid enough to be used among the clinicians for a better communication. (Table 3).

Table 3.

Inclusions in the third edition of AJCC-1988 [3]

Tumour (T)		Node (N)		Metastasis (M)
TX, TO, TIS, T1, T2, T3 T4	Similar to previous editions	NX, NO, N1, N2a, N2b	Similar to previous editions	Similar to previous editions
	Greatest diameter of primary tumour more than 4 cm	N2c	Metastasis to bilateral or contralateral lymph nodes less than 6 cm in their greatest dimension
	Lip—invasion of adjacent structures, i.e. cortical bone, tongue, skin of neck	N3	Metastasis in a lymph node greater than 6 cm in its greatest dimension
	Oral cavity—invasion of adjacent structures, i.e., cortical bone, deep muscle of tongue, maxillary sinus, skin

To begin with the T aspect of the classification, the primary difference as and when compared to the previous editions was the fact that tumour was divided under the sub-categories, lip and oral cavity. Though the classification was similar till the level of T3 [2], T4 was divided under lip and oral cavity, which specified the invasion of adjacent structures, i.e. cortical bone, tongue, skin of neck and cortical bone, deep muscle of tongue, maxillary sinus, skin for lips and oral cavity, respectively.

The N aspect was slightly modified in the third edition. For N2, which had two subdivisions earlier, i.e. N2a and N2b, N2c was added which denoted “metastasis to bilateral or contralateral lymph nodes less than 6 cm in their greatest dimension.”

The subdivision of N3 into three categories was excluded. The subdivision N3 only denoted “metastasis in a lymph node greater than 6 cm in its greatest dimension”. This seemed to look much simpler than the elaborate N classifications earlier.

The M aspect of the classification were similar to the second edition [2].

Stage grouping Coming to the staging based on TNM classification, stage 0 was introduced which included Tis No Mo. This stage was not a part of the previous editions.

Inclusions in the Fourth Edition-1992 [4]

Most of the fourth edition was similar in the aspects of TNM classification, histopathological grading, stage grouping, to the previous classification; however, the elaborate informative aspects which included location, characteristics of the tumour and involvement of the neighbouring region were introduced back, similar to the classification given in the first [1] and second editions [2]. As a reminder point, these three aspects were excluded in the classification given in the third edition (1992). (Table 4).

Table 4.

Sixth edition of AJCC-2002 [5]

Tumour (T)		Node (N)		Metastasis (M)
TX, TO, TIS, TI, T2, T3, T4a, T4b	Similar to previous editions	NX, NO, N1, N2, N2a, N2b, N2c, N3	Similar to previous editions	MX, MO, MI	Similar to previous editions
T4	T4 (lip)—Tumour invades through cortical bone, inferior alveolar nerve, floor of the mouth or skin of the face i.e., chin or nose
	T4a—RESECTABLE DISEASE Oral cavity—Tumour invades adjacent structures (e.g. through cortical bone, into deep extrinsic muscle of tongue {genioglossus, hyoglossus, palatoglossus, styloglossus}, maxillary sinus, skin of the face)
	T4b—UNRESECTABLE DISEASE Tumour invades masticatory space, pterygoid plates or skull base and/or encases the internal carotid artery

The Fifth Edition-1997 [6]

The T, N and M aspects of the classification, stage grouping, location, characteristics of the tumour and involvement of neighbouring regions—all the aspects were similar to the previous classification [4].

Staging in Previous Editions (I, II, III, IV)

Stage 0:	Tis	No	Mo
Stage I:	T1	No	Mo
Stage II:	T2	No	Mo
Stage III:	T3	No	Mo
	T1	N1	Mo
	T2	N1	Mo
	T3	N1	Mo
Stage IV:	T4	No, N1	Mo
	Any T	N2, N3	Mo
	Any T	Any N	M1

Staging in Fifth Edition

Stage 0:	Tis	No	Mo
Stage I:	T1	No	Mo
Stage II:	T2	No	Mo
Stage III:	T3	No	Mo
	T1	N1	Mo
	T2	N1	Mo
	T3	N1	Mo
Stage IVA:	T4	No	Mo
	T4	N1	Mo
	Any T	N2	Mo
Stage IVB:	Any T	N3	Mo
Stage IVC:	Any T	Any N	M1

Coming to the sixth edition, changes were made in the T aspect of the classification and also in the stage grouping. Rest were all similar to the previous classification in the fifth edition (1997) [6].

In the T aspect, the system followed the same depiction till T3 as in fifth edition (5), the change was introduced in the level of T4, where it was divided as T4 (lip), T4a and T4b.

T4 (lip)—Tumour invades through cortical bone, inferior alveolar nerve, floor of the mouth or skin of the face, i.e. chin or nose.

T4a—Oral cavity—Tumour invades adjacent structures (e.g. through cortical bone, into deep extrinsic muscle of tongue {genioglossus, hyoglossus, palatoglossus, styloglossus}, maxillary sinus, skin of the face).

T4b—Tumour invades masticatory space, pterygoid plates or skull base and/or encases the internal carotid artery.

T4a here is similar to the T4(lip) and T4 (oral cavity) combined together as in previous classifications; however, T4b is a new addition to the classification.

Difference in the Stage Grouping

T4a and T4b were termed resectable and unresectable diseases, respectively. This apparently led to division of stage IV in the previous edition into stages Iva, IVb and IVc.

The stage grouping was similar to the previous versions till stage III. (Table 5).

Table 5.

Seventh edition of AJCC-2010 [7]

Tumour (T)		Node (N)		Metastasis (M)
TX, TO, TIS, TI, T2, T3	Similar to previous editions	NX, NO, N1, N2, N2a, N2b, N2c, N3	Similar to previous editions	MO	No (known) distant metastasis
T4	T4 (lip)—Tumour invades through cortical bone, inferior alveolar nerve, floor of the mouth or skin of the face i.e., chin or nose			MI	Distant metastasis present
	T4a—Oral cavity—moderately advanced local disease: Tumour invades adjacent structures (e.g. through cortical bone, into deep extrinsic muscle of tongue {genioglossus, hyoglossus, palatoglossus, styloglossus}, maxillary sinus, skin of the face)
	T4b—very advanced local disease: Tumour invades masticatory space, pterygoid plates or skull base and/or encases the internal carotid artery

Stage IV, unlike that previously, was further subdivided into stages IV a, IV b and IV c.

IV a:	T4a	No/N1/N2	Mo
	T1/2/3	N2	Mo
IV b:	Any T	N3	Mo
	T4b	Any N	Mo
IV c:	Any T	Any N	M1

The T aspect of the classification was the same till T3 and also similar to T4a and T4b as in previous version [5]; however, the phrases “moderately advanced local disease” and “very advanced local disease” were added in T4a and T4b, respectively.

It is claimed that the addition of this phrase denotes that just a superficial erosion of bone/ tooth socket by the gingival primary is not sufficient enough to classify a tumour as T4. Hence, the term advanced specifies that the tumour is not just a superficial erosion anymore and, hence, is classified under T4.

The N aspect has been the same since the third edition (1988) and continues to be the same in the seventh edition as well.

The M aspect included M0 (No distant metastasis) and M1 (distant metastasis). MX was eliminated.

T4 lesions have been divided into T4a (moderately advanced local disease) and T4b (very advanced local disease), leading to the stratification of Stage IV into Stage IVA (moderately advanced local/regional disease), Stage IVB (very advanced local/regional disease), and Stage IVC (distant metastatic disease). (Table 6).

Table 6.

Newly added aspects of the seventh edition

Required for staging	None
Clinically significant	Size of lymph nodes Extracapsular extension from lymph nodes for head and neck Head and neck lymph nodes levels I–III Head and neck lymph nodes levels IV–V Head and neck lymph nodes levels V–VII Other lymph node group Clinical location of cervical nodes Extracapsular spread (ECS)Clinical Extracapsular spread (ECS)Pathologic Human Papilloma Virus (HPV) status Tumour thickness

Newly Added Aspects of the Seventh Edition

1. Prognostic factors (site specific factors):

PROGNOSTIC FACTORS (SITE-SPECIFIC FACTORS)

• 2.Prefixes and suffixes:

These help in the identification of special cases is what is claimed in the seventh edition. They do not affect the stage grouping but might require separate analysis during treatment planning an destination of prognosis.

• Prefix ‘c’ Clinical staging

• Prefix ‘p’ Pathological staging

• Prefix ‘m’ Presence of multiple primary tumours in a single site, e.g. T(m)NM.

• Prefix ‘y’ Classification is performed during or following initial multimodality therapy.

• Prefix ‘r’ Recurrent tumours when staged after a disease-free interval.

• Prefix ‘a’ Determined in autopsy stage.

• 3.Additional descriptors:

The lymphatic vessel invasion (L) and venous invasion (V) was combined together under lymph-vascular invasion (LVI) by the Cancer Registrars.

• LVI—Not present/not identified

• LVI—Present/identified

• Not applicable

• Unknown/indeterminate

All these aspects including the changes and the additional descriptors provide a comprehensive, elaborate and vivid review of the case, patient and the tumour characteristics. However, it includes multiple sub-headings and is more elaborate than the classifications described till date. This might have prompted for a classification similar to it in terms of comprehension and information, but less laborious and easier-to-use. (Tables 7, 8, 9).

Table 7.

T staging of eighth edition of AJCC-2017 [8]

TX Tis T1 T2 T3	Primary tumour cannot be assessed Carcinoma in situ Tumour ≤ 2 cm and DOI ≤ 5 mm Tumour ≤ 2 cm, DOI > 5 mm, and ≤ 10 mm or tumour > 2 cm and ≤ 4 cm and DOI ≤ 10 mm Tumour > 4 cm or any tumour with DOI > 10 mm
T4
T4a	Tumour invades adjacent structures only (e.g. through cortical bone of mandible or maxilla, or involves the maxillary sinus or skin of the face)
T4b	Tumour invades masticator space, pterygoid plates, or skull base and/or encases the internal carotid artery

Table 8.

Clinical N staging eighth edition of AJCC-2017 [8]

	Clinical
NX N0 N1 N2	Regional lymph nodes cannot be assessed No regional lymph node metastasis Metastasis in a single ipsilateral lymph node, ≤ 3 cm and ENE− Metastasis in a single ipsilateral lymph node > 3 cm and ≤ 6 cm and ENE−; or metastases in multiple ipsilateral lymph nodes, ≤ 6 cm and ENE−; or in bilateral or contralateral lymph nodes, ≤ 6 cm and ENE−
N2a	Metastasis in a single ipsilateral lymph node > 3 cm and ≤ 6 cm and ENE−
N2b	Metastases in multiple ipsilateral lymph nodes, ≤ 6 cm and ENE−
N2c	Metastases in bilateral or contralateral lymph nodes, ≤ 6 cm and ENE−
N3	Metastasis in a lymph node > 6 cm and ENE- or metastasis in any node(s) and clinically overt ENE+
N3a	Metastasis in a lymph node > 6 cm and ENE−
N3b	Metastasis in any node(s) and clinically overt ENE+;

Table 9.

Pathological N staging of eighth edition of AJCC-2017 [8]

	Pathological
NX N0 N1 N2	Regional lymph nodes cannot be assessed No regional lymph node metastasis Metastasis in a single ipsilateral lymph node, ≤ 3 cm and ENE− Metastasis in a single ipsilateral lymph node, ≤ 3 cm and ENE+; or metastasis in a single ipsilateral lymph node > 3 cm and ≤ 6 cm and ENE−; or metastases in multiple ipsilateral lymph nodes, ≤ 6 cm and ENE−; or in bilateral or contralateral lymph nodes, ≤ 6 cm and ENE−
N2a	Metastasis in a single ipsilateral lymph node, ≤ 3 cm and ENE+, or metastasis in a single ipsilateral lymph node > 3 cm and ≤ 6 cm and ENE−
N2b	Metastases in multiple ipsilateral lymph nodes, ≤ 6 cm and ENE − N2c Metastases in bilateral or contralateral lymph nodes, ≤ 6 cm and ENE−
N3	Metastasis in a lymph node > 6 cm and ENE-; or 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+
N3a	Metastasis in a lymph node > 6 cm and ENE−
N3b	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+

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 E N E (−) or ENE(+).

The two aspects that were newly introduced in the classification were:

1. Depth of invasion (T aspect).

2. Extranodal extension (N aspect).

Both the factors have been known to show differences in the estimation of prognosis and the disease-free survival of the patient. Hence, these were included in the classification.

Additional factors recommended for clinical care in 8th edition are resection margins, worst pattern of invasion, perineural invasion, lymphovascular invasion, overall health, comorbidity, lifestyle factors and tobacco use.

Discussion

The initial work on the clinical classification of cancer was instituted by the League of Nations Health Organization and other healthcare organizations since 1929, the Union for International Cancer Control (UICC) became most active in the field through its Committee on Clinical Stage Classification and Applied Statistics (1954) [9]. In November 1969, in a joint meeting of the AJCC (American Joint Committee on Cancer) and UICC, the two groups agreed that they would have a discussion before obligation of a classification scheme by either group. In 1970, the AJC adopted “objectives, rules and regulations of the AJC,” which resulted in the formulation and publication of systems of classification of cancer [10]. Since its inception, the AJCC has embraced the TNM system and has used it as its foundation to describe the anatomic extent of cancer at the time of initial diagnosis and before the application of definitive treatment. In addition, a classification of the stages of cancer was used as a guide for treatment and prognosis and for comparison of outcomes in cancer management. In 1976, the AJCC sponsored a National Cancer conference on Classification and Staging [11]. The deliberation at this conference led directly to the development of the AJCC Cancer Staging Manual, 1st Edition, which was published in 1977 and allowed the AJCC to broaden its scope and recognize its leadership role in the staging of cancer for American physicians and registrars [8]

Ever since the beginning, various modifications of the classification were introduced and released by the joint collaboration of AJCC and UICC in various editions of cancer staging manuals [1–8]. However, the present review article was kept focused onto the changes introduced in the staging of cancers of oral cavity only, in particular. These changes came a long way since 1944, to the eighth edition of cancer staging manual published much recently, in 2017 [8]. Though there was a major increase in the number of verticals appreciated and mentioned, the fact that the classification has become lengthy and cumbersome to many is something which might not be denied easily.

The Evolution of the TNM Classification

The ‘T’ aspect which initially was written only in terms of size and extent of the lesion, later included the regional invasiveness also, in terms of lip, oral cavity and the surrounding structures, since the third edition and was continued ever since then. In the much recent eighth edition [8], a newer dimension, the depth of invasion in terms of millimetres, was also added [12, 13].

The ‘N’ aspect, however, did not take many modifications as such, ever since third edition [3] after it was slightly simplified than the first one. In the eighth edition, a newer term was again added to the nodal aspect, being the ExtraNodal Extension (ENE) [8].

The ‘M’ aspect of the classification didn’t see any significant difference right from the beginning.

The seventh edition included certain verticals left undiscussed till then [7], being site-specific prognostic factors, certain prefixes and suffixes and additional descriptor terms, all of which were discussed earlier during the mention of the seventh edition.

According to Hubertlow, tumour thickness is an important factor to determine prognosis and adds certain value to the TNM staging system. This, was not included in the seventh edition.

The importance of imaging and inclusion of elaborate nodal classification might have been additive for the prognostic value of the seventh edition. However, these have been included in the eighth edition later.

Despite recognition of the importance of the R (Residual tumour) classification for patient management and a prognostic indicator, inconsistencies in application and interpretation of the R classification have been reported to occur frequently [14]. However, this has not been included in the seventh edition.

Inclusion of imaging The eighth edition included the information about the most appropriate imaging evaluation in each disease site. The imaging section in each chapter describes which imaging tests are most appropriate for assessing tumour stage information. This is a required and notable inclusion to the seventh edition.

The two new concepts included into the eighth edition that were debatable among the fraternity were.

• i.Depth of invasion
• ii.Extranodal extension [15, 16] 

Lee et al. in 2019 [17] evaluated the incidence and prognostic importance of stage migration as a result of these changes in the AJCC 8 staging system. A cohort study was conducted by analysing patients from the National Cancer Database who underwent definitive surgery for oral cavity squamous cell carcinoma between the time frame of 2004 and 2013. They concluded that Depth of invasion and extranodal extension have a prognostic validation and supported their inclusion in the eighth edition. Though they result in some upstaging of the disease, this might be useful in the adjunct treatment aspect to the patient. However, they caution the judicious use of these factors as inclusive criteria during the staging.

Amit et al. in 2020 also conducted a retrospective analysis on 1258 patients who underwent surgery between the time frame of 1995 and 2019 in the Anderson Cancer Center, Texas. They measured the outcome based on the disease specific survival (DSS) and the metastasis-free survival and concluded that the inclusion of extranodal extension in the classification proved to be an important prognostic determinant along with the metastatic lymph node assessment [11].

The eighth edition did not include the electronic database for the patients’ records. In the era of developing software technologies and their advancements, digitalization of the data has become a mandatory evidence for the determination of prognosis and also post-treatment evaluation. The editorial committee and the members of AJCC also emphasized on the need for inclusion of more members from various medical branches into the organization for their suggestions and inputs regarding improving on the existing TNM staging systems [18]. (Table 10).

Table 10.

Brief discussion on all staging systems

	1st edition	2nd edition	3rd edition	4th edition	5th edition	6th edition	7th edition	8th edition
T	Tx–T4	–	Lips and oral cavity included under T4	Location, characteristics of tumour and involvement of neighbouring region	–	T4—lip T4a—oral cavity T4b—tumour invades masticatory space, pterygoid plates or skull base and/or encases the internal carotid artery	T4—lip T4a—oral cavity (moderately advanced local disease) Tumour invades adjacent structures (e.g. through cortical bone, into deep extrinsic muscle of tongue {genioglossus, hyoglossus, palatoglossus, styloglossus}, maxillary sinus, skin of the face) T4b—severely advanced local disease tumour invades masticatory space, pterygoid plates or skull base and/or encases the internal carotid artery	Depth of invasion has been added
N	Nx–N3	N3 has been simplified	–	–	–	–	Clinical and pathological staging has been added	Clinical and pathological staging has been added Extranodal extension has been added
M	M0, Mx, M1	–	–	–	–	–	–	–

Limitations

The present updated TNM staging undoubtedly provides better diagnostic data regarding the patient’s situation, describing the clinical, anatomic and histological features. It also gives a much vivid idea in determining the prognosis of a clinical scenario. However, the classification looks more elaborate and cumbersome. Multiple parts of the classification, particularly the nodal involvement, metastatic changes, etc., have been almost unchanged or slightly modified. In the era of improved efficacy of diagnostic methodologies, radiological imaging for example, their significance in determining the prognosis has not been added/not been mentioned about. The communication might still remain perplexing to few clinicians due to its elaborative nature. This might induce certain level of disparity [19].

Future Perspectives

An elaborate and a comprehensive classification like the present TNM staging always provides proper understanding over the prognostic factors. However, a diagnostic coding which is short and crisp, but would include more information related to the clinical scenario, would be better preferred over the detailed description of every condition in words. Colour coding in combination with the diagnostic coding might also provide the idea and might be better communicated among the clinicians. Inclusion of the investigatory diagnostic values, like imaging results can be included. Nomograms are graphical calculation devices which can predict individual prognosis with high accuracy and are likely used in near future [19, 20].

Conclusion

The disparities in surgical and oncological care are a point to discuss, along with the advancements in imaging, education and predicting or prognostic factors for various cancers [21].

The present review is scripted to emphasize and elaborate in detail, the evolution of the TNM classification ever since its inception in 1944 till much recent times. This was quite useful in determining the clinical stage of the tumour, much recent additions adding up in determining the accurate prognostic value and evaluation, both surgical and post-surgical. However, the more descriptive and informative a classification becomes, the more cumbersome it would be, for implementation and effective clinical usefulness. In spite of the undeniable fact of the requirement of a detailed description of all the verticals included, it is also mandatory that a classification should be easier for communication, besides conveying the required data. Thus, there might be a constant demand and drafting of protocols to build and remodel a classification, so that it would ideally deliver the concepts of required clinical description and easy communication.

Funding

None.

Declarations

Conflict of interest

There are no conflicts of interest.