Classification, Grading, and Staging
Recent advancements in the understanding of the genetics of RCC
have led to a new pathological classification of five different subtypes of
RCCs: clear cell, papillary, chromophobe, collecting duct carcinoma (Bellini
Duct tumor), and renal carcinoma unclassified (renal medullary carcinoma). This
classification is primarily based on cytologic appearance and the cell origin
in combination with growth pattern and genetic alterations (Campbell &
Lane, 2012; Kennedy et al., 1990).
The grading of RCC is based on the morphology of a neoplasm with
hematoxylin and eosin (H&E) staining on microscopy. The most popular and
widely used system for grading RCC is a nuclear grading system described by
Fuhrman, Lasky, and Limas in 1982. This system categorizes RCC into one of four
grades based on nuclear characteristics and has been shown to correlate with
prognosis (see Table
3).
Table
3. Fuhrman Grading System
|
Grade
|
Description
|
|
Grade 1
|
Nuclei of the tumor cells are small (< 10
μm), hyperchromatic, and round (resembling mature lymphocytes), with no
visible nucleoli and little detail in the chromatin.
|
|
Grade 2
|
Nuclei of the tumor cells are slightly larger
(15 μm) with finely granular "open" chromatin but small,
inconspicuous nucleoli.
|
|
Grade 3
|
Nuclei of the tumor cells are larger (20 μm in
size) and may be oval in shape, with coarsely granular chromatin. The
nucleoli are easily recognizable.
|
|
Grade 4
|
The nuclei are pleomorphic with open chromatin
or hyperchromatic and single or multiple macronucleoli.
|
Source: Fuhrman et al.,
1982.
The Tumor Node Metastasis (TNM) staging system is used for staging
all histologic variants of renal carcinoma. This system assesses the anatomic
extent of disease and has been shown to correlate with prognosis. A revision
was proposed in 2010 and is supported by the American Joint Committee on Cancer
(AJCC) (2010) (see Table
4).
Table
4. Tumor Node Metastasis
|
Primary
|
Tumor (T) Description
|
|
TX
|
Primary tumor cannot be assessed
|
|
T0
|
No evidence of primary tumor
|
|
T1
|
Tumor 7 cm or less, limited to 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 dimen-sion, and limited to the kidney
|
|
T2
|
Tumor greater than 7 cm, limited to 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/adrenal/perinephric tissue; not beyond Gerota's fascia
|
|
T3a
|
Tumor invades perinephric tissue, renal sinus
or renal vein
|
|
T3b
|
Tumor extends into renal vein(s) or vena cava
below diaphragm
|
|
T3c
|
Tumor extends into vena cava above diaphragm
or into wall of vane cava at any level
|
|
T4
|
Tumor invades beyond Gerota's fascia or
directly into adrenal gland
|
|
N-
|
Regional lymph nodes
|
|
NX
|
Regional nodes cannot be assessed
|
|
N0
|
No regional lymph node metastasis
|
|
N1
|
Metastasis in a single regional lymph node
|
|
N2
|
Metastasis in more than one regional lymph
node
|
|
M-
|
Distant metastasis
|
|
MX
|
Distant metastasis cannot be assessed
|
|
M0
|
No distant metastasis
|
|
M1
|
Distant metastasis
|
Source: Edge et al., 2010.
Another commonly used staging system ranges from Stage I to IV
based on anatomic stage and places into a prognostic group (see Table
5).
Table
5. Anatomic Staging System/Prognostic Group
|
Anatomic Stage
|
Prognostic Group
|
|
|
Stage 1
|
T1 N0 M0
|
 |
|
Stage 2
|
T2 N0 M0
|
|
|
Stage 3
|
T1 or T2, N1 M0
|
T3 N0 or N1, M0
|
|
Stage 4
|
T4 any N M0
|
Any T, any N, M1
|
Source: Edge et al., 2010.
It is hoped that with greater
knowledge of tumor genetics and immunohistochemistry, there will be an improved
ability to make prognoses and appropriately target therapy to those who would
most benefit (Odonez & Hank, 2011).
