Information on anatomical extent of disease at presentation or stage is central to cancer surveillance to determine cancer burden as it provides additional valuable information to incidence and mortality data. However, cancer registries in low- and middle-income countries frequently have insufficient information to determine complete TNM data, either because of inability to perform necessary investigations or because of lack of recording of information. In view of this, the UICC TNM Project, together with the International Agency for Research in Cancer and the National Cancer Institute, has developed a new classification system, “Essential TNM”, which can be used to collect stage data when complete information is not available. To date Essential TNM schemas have been developed for breast, cervix, colon, and prostate cancer, and are presented in the  TNM Classification of Malignant Tumours Eighth Edition.

When the T, N, and M categories have not been recorded in the clinical records or if the data to determine the categories is not available, Using the schema for breast, colorectal cancer, prostate or cervix cancer the extend of disease may be recorded as Stage I,II,III,or IV or if insufficient data as distant, regional or localized.

Rules for Classification

Essential TNM is composed of three key elements that together summarize the extent of cancer in the patient.  

M:  Presence or absence of distant metastasis   

N:   Presence or absence of regional node metastasis/involvement                    

T:   Extent of invasion and/or size of the tumour

Coding the Elements of Essential TNM

Metastasis (M)

M+       Presence of distant metastasis including non-regional nodes

M-        No mention of distant metastases, clinically or pathologically

Regional Node Metastasis/Involvement (N)    

R+        Presence of regional node metastasis/involvement

R-         No mention of regional node metastases, clinically or pathologically

Extent of Invasion and/or Size of Tumour (T)

Depending on the information available the T category can be recorded of if not available the extent of the local tumour as advanced or localized as below:

A       Extent of invasion and/or tumour size is Advanced

A2 - Extent of invasion and/or tumour size is very advanced

A1 - Extent of invasion and/or tumour size is advanced

 L      Extent of invasion and/or tumour size is Limited

L2 - Extent of invasion and/or tumour size is limited

L1 - Extent of invasion and/or tumour size is very limited

X       Extent of invasion and/or tumour size cannot be assessed