4. STAGING AND CLASSIFICATION SYSTEMS
4.1. Staging
The Tumour Node Metastasis (TNM) classification system is recommended for clinical and scientific use [81]. A supplement was published in 2012, and the latter’s prognostic value was confirmed in single- and multi-institution studies [82,83]. Tumour size, venous invasion, renal capsular invasion, adrenal involvement, LN and distant metastasis are included in the TNM classification system (Table 4.1). However, some uncertainties remain:
- The sub-classification of T1 tumours using a cut-off of 4 cm might not be optimal in NSS for localised cancer [84];
- The value of size stratification of T2 tumours has been questioned [85];
- Renal sinus fat invasion might carry a worse prognosis than perinephric fat invasion but is nevertheless included in the same pT3a stage group [86-89] (LE: 3);
- Sub T-stages (pT2b, pT3a, pT3c and pT4) may overlap [83];
- For adequate M staging, accurate pre-operative imaging (chest and abdominal CT) should be performed [90,91] (LE: 4).
A proposed imaging analysis of Tumour Contour Irregularity might be a valuable tool to enhance the preoperative staging between T1 and T3a RCCs for treatment decisions [92].
The TNM classification should not be considered the only criterion for clinical decision-making, but patient’s condition, comorbidities and wishes are of fundamental importance to select the most optimal treatment. A clinically-guided RCC staging classification was proposed in 2022 by the EAU panel, based on changes observed in the management of small renal masses (SRM), locally advanced and metastatic disease [84].
Table 4.1: 2017 TNM classification system [93]
| 2017 TNM classification system | ||||
| T - Primary tumour | ||||
| TX | Primary tumour cannot be assessed | |||
| T0 | No evidence of primary tumour | |||
| T1 | Tumour ≤ 7 cm or less in greatest dimension, limited to the kidney | |||
| T1a | Tumour ≤ 4 cm or less | |||
| T1b | Tumour > 4 cm but ≤ 7 cm | |||
| T2 | Tumour > 7 cm in greatest dimension, limited to the kidney | |||
| T2a | Tumour > 7 cm but ≤ 10 cm | |||
| T2b | Tumours > 10 cm, limited to the kidney | |||
| T3 | Tumour extends into major veins or perinephric tissues but not into the ipsilateral adrenal gland and not beyond Gerota fascia | |||
| T3a | Tumour extends into the renal vein or its segmental branches, or invades the pelvicalyceal system or invades perirenal and/or renal sinus fat*, but not beyond Gerota fascia* | |||
| T3b | Tumour grossly extends into the vena cava below diaphragm | |||
| T3c | Tumour grossly extends into vena cava above the diaphragm or invades the wall of the vena cava | |||
| T4 | Tumour invades beyond Gerota fascia (including contiguous extension into the ipsilateral adrenal gland) | |||
| N - Regional Lymph Nodes | ||||
| NX | Regional lymph nodes cannot be assessed | |||
| N0 | No regional lymph node metastasis | |||
| N1 | Metastasis in regional lymph node(s) | |||
| M - Distant metastasis | ||||
| M0 | No distant metastasis | |||
| M1 | Distant metastasis | |||
| pTNM stage grouping | ||||
| Stage I | T1 | N0 | M0 | |
| Stage II | T2 | N0 | M0 | |
| Stage III | T3 | N0 | M0 | |
| T1, T2, T3 | N1 | M0 | ||
| Stage IV | T4 | Any N | M0 | |
| Any T | Any N | M1 | ||
A help desk for specific questions about TNM classification is available at http://www.uicc.org/tnm. *Adapted based on the American Joint Committee on Cancer (AJCC), 8th Edn. 2017 [94]
4.2. Anatomic classification systems
Objective anatomic classification systems, such as the Preoperative Aspects and Dimensions Used for an Anatomical (PADUA) classification system, the R.E.N.A.L. nephrometry score, the C-index, an Arterial Based Complexity (ABC) Scoring System and Zonal NePhRO scoring system, have been proposed to standardise the description of renal tumours [95-97]. These systems include assessment of tumour size, exophytic/endophytic properties, proximity to the collecting system and renal sinus, and anterior/posterior or lower/upper pole location. Increasing tumour shape irregularity on imaging is associated with an increased risk of pT3a upgrading and grade 3-4 disease, but the positive marign rate was similar [98].
The use of such a system is helpful as it allows objective prediction of potential morbidity of NSS and tumour ablation techniques. These tools provide information for treatment planning, patient counselling, and comparison of PN and tumour ablation series. However, when selecting the most optimal treatment option, anatomic scores must be considered together with patient features and surgeon experience.