Renal cell carcinoma classification
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Classification of renal cell carcinomas according to histopathological subtypes is based on the 1997 classification by Heidelberg and colleagues. Classification may also be according to the stage of renal cell carcinoma, which often is based on Robson classification system or the tumor-lymph node-metastasis (TNM) system.
The following tables classify renal cell carcinoma according to histologic appearance and differentiates sporadic from hereditary forms of renal cell carcinoma. Clear type (also called Conventional type) renal cell carcinoma is considered the most common type of renal carcinoma. The most common classification of renal cell carcinoma is based on the histopathological appearance of the tumor. There are currently six subtypes of renal cell carcinoma, most common of which are the conventional (also called clear cell) renal carcinoma, accounting for approximately 75% of all cases. Renal cell carcinoma may also be clinically classified based on the staging of the tumor, as shown below.
|Histologic Appearance||Incidence (%)|
|Conventional (Clear Cell)||75|
|Collecting Duct||< 1|
|Unclassified||3 - 5|
Staging of Renal Cell Carcinoma
Clear cell renal carcinomas can be classified according to staging or anatomic spread of the disease. Two commonly implemented systems are the Modified Robson's System (1969) and the TNM (Tumor - Nodes - Metastasis) System:
The Modified Robson's staging system has been proposed in 1969. It emphasizes the anatomic distribution of the tumor and proximity to important vasculature and lymph nodes with prognostic implications, reporting a 52% 5-year survival and a 66% 5-year survival in patients with localized tumor.
|Stage I||Tumor confined within parenchyma|
|Stage II||Tumor involves perinephric fat, but still confined within Gerota's fascia|
|Stage III|| A) Tumor involves main renal vein or vena cava |
B) Tumor involves regional lymph nodes
C) Tumor involves both local vessels and lymph nodes
|Stage IV|| A) Tumor involves adjacent organs other than adrenal gland |
B) Distant metastasis
The TNM classification system for staging of renal clear cell carcinoma is commonly used. The following TNM classification is based on the American Joint Committee Cancer (AJCC), the American College of Radiology (ACR), and the Union for International Cancer Control (UICC).
|Primary Tumor (T)|| TX: Primary tumor cannot be assessed |
T0: No evidence of primary tumor
T1: Tumor 7 cm or less in greatest dimension, limited to the kidney
T1a: Tumor 4 cm or less in greatest dimension, limited to the kidney
T1b: Tumor more than 4 cm but not more than 7 cm in greatest dimension, limited to the kidney
T2: Tumor more than 7 cm in greatest dimension, limited to the kidney
T2a: Tumor more than 7 cm but less than or equal to 10 cm in greatest dimension, limited to the kidney
T2b: Tumor more than 10 cm, limited to the kidney
T3: Tumor extends into major veins or perinephric tissues, but not into the ipsilateral adrenal gland and not beyond Gerota's fascia
T3a: Tumor grossly extends into the renal vein or its segmental (muscle containing) branches, or tumor invades perirenal and/or renal sinus fat but not beyond Gerota's fascia
T3b: Tumor grossly extends into the vena cava below the diaphragm
T3c: Tumor grossly extends into the vena cava above the diaphragm or invades the wall of the vena cava
T4: Tumor invades beyond Gerota's fascia (including contiguous extension into the ipsilateral adrenal gland)
|Regional Lymph Nodes (N)|| NX: Regional lymph nodes (LN) cannot be assessed |
N0: No regional LN metastases
N1: Metastasis in a single LN 2 cm or less
N2: Metastasis in a single LN greater than 2 cm, but less than 5 cm, or multiple LN none greater than 5 cm
N3: Metastasis in LN greater than 5 cm
|Distant Metastasis (M)|| M0: No distant metastasis |
M1: Distant metastasis
To note, proposals in December 2013 to amend the TNM staging of renal clear cell carcinoma have emerged following a 41.7 month follow-up of 122 patients with pT3a renal cell carcinoma. Baccos and colleagues concluded that fat and/or renal vein invasion are important prognostic factors that play a major role in patient survival and should be considered in the TNM staging. Patients with both fat invasion and renal vein thrombosis have worse survival rates than those with only one element.
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- Baccos A, Brunocilla E, Schiavina R, Borghesi M, Rocca GC, Chessa F et al. (2013). "Differing risk of cancer death among patients with pathologic t3a renal cell carcinoma: identification of risk categories according to fat infiltration and renal vein thrombosis.". Clin Genitourin Cancer 11 (4): 451-7. doi:10.1016/j.clgc.2013.05.006. PMID 23816525.