Pathology and pathophysiology of renal carcinoma
The 2004 classification retained the four subtypes of renal clear cell carcinoma, papillary renal cell carcinoma (type I and II), renal suspicious cell carcinoma and unclassified renal cell carcinoma from the 1997 classification, and further divided the collecting duct carcinoma into Bellini’s collecting duct carcinoma and renal medullary carcinoma, in addition to adding multifoveal cystic renal cell carcinoma, Xp11.2 translocation/TFE3 gene fusion-associated renal carcinoma, neuroblastoma The new classification places more emphasis on the pathology and the relationship between the kidney cells and the kidney. The new classification places more emphasis on the linkage between pathology and clinic, and pays more attention to the relationship between different pathological types and prognosis. Of course, the new classification still needs to be improved gradually, and with the continuous progress of molecular biology research of tumors, more accurate molecular markers will be available for the classification and staging of tumor types.
Tumors are mostly solitary, spherical, and seen in both poles of the kidney, especially in the upper pole, and often cause deformation of the kidney. The tumor often has a pseudo-envelope formation and is therefore well defined from the surrounding renal tissue. The tumor is mostly solid, a few are cystic, grayish yellow (cancer cells contain a lot of lipid in the cytoplasm) or grayish white, often with hemorrhage (reddish brown), necrosis (grayish white) and fibrosis (white) areas, showing colorful colors. Under light microscopy, the cancer cells were mostly arranged in a glandular vesicle shape, but also in a ductal or papillary shape, mostly in solid nests, and a few in a cystic shape. The interstitium between the cancer nests is rich in capillaries, with few fibrous components.
1.clear cell carcinoma
Clear cell renal cell carcinoma has a high incidence at the age of 50-70 years, with a male to female ratio of about 2:1. 33%-50% of asymptomatic renal carcinoma is found in kidneys. The clinical manifestations may include hematuria, lumbar pain, and paraneoplastic syndrome in 10%-40% of patients, and CT enhancement scan is characterized by “fast forward and fast backward”.
Clear cell carcinoma accounts for about 60%-85% of RCC. Most sporadic renal clear cell carcinomas are unilateral single lesions, while 2%-5% of patients have bilateral or unilateral multicentric lesions at the same time or sequentially, while hereditary renal clear cell carcinomas are mostly bilateral multifocal. Most of the specimens of renal clear cell carcinoma are solid, yellow in color because of the lipid content of cancer cells, necrosis and hemorrhage are common in the tumor, 10%-25% of the clear cell carcinoma tissues have cystic changes, 10%-20% of the cancer tissues have dotted or patchy calcification, which makes the surface colorful. Microscopically, the cytoplasm of cancer cells is transparent and hollow, forming dense glandular vesicles and tubular and cystic structures, and there is a network of slender blood vessels within the tumor. The prognosis of patients with cystic transformation is better than that of patients with solid clear cell carcinoma. 2%~5% of clear cell carcinoma tissues contain sarcoma-like structures, suggesting poor prognosis.
2.Papillary renal cell carcinoma
Papillary renal cell carcinoma is similar to renal clear cell carcinoma in terms of age of onset, incidence rate of both sexes, and symptoms and signs. It is commonly seen in patients with long-term hemodialysis and acquired renal cystic disease. It is generally believed that papillary renal cell carcinoma has no specificity in imaging, but we found in our clinical work that it appears as a tumor with ischemic blood supply on CT-enhanced scan, and tumor enhancement is not as obvious as that of typical clear cell carcinoma.
Papillary renal cell carcinoma accounts for about 7%-14% of RCC. Lesions involving bilateral kidneys and multifocal are relatively common. Tumors are mostly grayish-pink in color, with hemorrhage, necrosis, cystic changes are common, soft and granular in texture, and sandy appearance in some areas. Microscopically, it is characterized by papillary or tubular papillary structures, with foamy macrophages and cholesterol crystals visible in the papillary core. It can be divided into type I: tumor cells are small, cytoplasm is sparse, and cells are arranged in a monolayer. Type II: Tumor cells have abundant eosinophilic cytoplasm, high nuclear grade, and pseudostratified nuclei. Papillary renal cell carcinoma type I multifocal lesions are more common than type II. Early findings show that papillary renal cell carcinoma has better prognosis than renal clear cell carcinoma, among which type I patients are better than type II.
3.Chromocytoma
Chromophobe renal cell carcinoma has an average age of 60 years, and the incidence rate of men and women is about equal, without special symptoms and signs.
Smoldering cell carcinoma accounts for about 4%-10% of RCC. The tumor is mostly a solitary solid tumor without envelope but with clear border, and the cut surface is brown with uniform texture. Microscopically, the cancer cells are large and lightly stained, the cell membrane is very clear, the cytoplasm is granular, and the perinuclear halo is empty.
4.Multi-atrial cystic renal cell carcinoma
Multilocular cystic renal cell carcinoma has an incidence of 3:1 in both sexes, and it can be shown as multilocular cystic mass by ultrasound, CT and MRI, with uneven interval thickening and calcification of cystic wall or separation in about 20% of cases.
Multi-compartmental cystic renal cell carcinoma is rare. The tumor tissue is well-defined, and the cystic cavity is of different sizes and filled with plasma or hemorrhagic fluid. The largest diameter of the tumor can be more than 10 cm, or even completely composed of cystic cavities. Microscopically, the tumor is multi-compartmental and cystic, and the cyst wall is lined with clear cancer cells, and aggregated clear cancer cells are also seen in the interval of the cyst. Multi-compartmental cystic renal cell carcinoma develops slowly and has good prognosis.
5.Collecting duct carcinoma
The age of onset of carcinoma of the collecting ducts of Bellini is relatively young, averaging 55 years old. Patients often present with abdominal pain, a mass in the quarter and hematuria. The disease is difficult to diagnose, and there are no typical imaging findings. Bellini’s tubular carcinoma accounts for about 1-2% of RCC and is mostly diagnosed at an advanced stage.
It is often located in the central part of the kidney, with solid, grayish-white tumor surface and irregular border. It often extends from the medullary center to the renal cortex or the hilum, and some tumors may grow into the renal pelvis. Microscopically, the cancer cells have the characteristics of adenocarcinoma and metastatic cell carcinoma, and another characteristic is that the covered cells of the tubular lumen are in the shape of flat-tipped shoe nails.
6.Renal medullary carcinoma
Renal medullary carcinoma is common in young people with sickle cell hematologic disease, with an average age of 10-40 years old and an incidence rate of 2:1 for men and women.
The origin of renal medullary carcinoma is not clear. It often occurs in the central part of the kidney, with solid, grayish-white, indistinct borders and visible necrosis in the cut surface. The tumor cells are arranged in adenoid cystic structure, and more neutrophil infiltration is seen in the tumor, and sickle-shaped red blood cells are also seen.
7.Translocation/TFE3 fusion-associated renal cancer
Renal carcinoma associated with Xp 11.2 translocations/TFE3 gene fusions is rare, mainly seen in children and young adults, but rare in older adults. The most characteristic morphological manifestation is a papillary structure composed of hyaline cells, and genetic examination shows different translocations of chromosome Xp11.2, all of which result in TFE3 gene fusions. Most of them are already in the progressive stage at the time of detection.
8.Neuroblastoma-associated renal cell carcinoma
Renal cell carcinoma associated with neuroblastoma is rare, mostly in patients who have survived for a long time after treatment for nephroblastoma in children, and rarely in patients with concurrent neuroblastoma associated with renal cell carcinoma. The incidence is the same in men and women. The morphological manifestation of the tumor varies from case to case, and may appear as clear cell carcinoma or papillary structure.
9.Mucinous tubular and spindle cell carcinoma
Mucinous tubular and spindle cell carcinoma is rare, the age of onset is 17-82 years old, the average age is 53 years old, the incidence rate of men and women is 1:4. Histomorphology is characterized by mucus-like tubular and spindle-shaped cells.
10.Unclassified renal cell carcinoma
It is a group of renal cell carcinoma which is difficult to be classified according to WHO histological criteria. It is morphologically polymorphic and clinically highly invasive, and has a poor prognosis. Its incidence is low, the literature is scarce, and it has yet to be summarized by clinicopathological and molecular genetic studies in larger samples. The tumor cells show pleomorphism, with some areas arranged in adenoidal, follicular, striated, or solid sheets, and areas of spindle-shaped tumor cells and tumor giant cells are seen. The tumor cells had abundant cytoplasm and obvious nucleoli. There were also varying degrees of hemorrhage and necrosis. Immunohistochemistry: tumor cells are Vimentin (+), CK, EMA, CD10, CK7 partially positive, CK20, 34βE12 are negative, P53 positive rate 30%-70%.
11.Dissemination route
Tumor grows gradually and can directly invade renal pelvis, calyces and even ureter. Cancer cells can penetrate the renal peritoneum and invade the adrenal gland and perinephric adipose tissue. In addition, renal cell carcinoma often invades the renal vein, and some of them form strips in the lumen of the vein to extend to the lower vena cava and even to the right atrium. Cancerous tissues are rich in blood vessels, so blood metastasis can occur at an early stage, most often to the lung, bone marrow and the opposite kidney. Lymphatic metastasis often first reaches the hilar and para-aortic lymph nodes.