Specimen

— fine needle aspirate/needle core biopsy/partial nephrectomy/nephrectomy ± ureterectomy/radical nephrectomy (kidney, pelvis, perirenal fat out to Gerota's fascia, adrenal gland, and a length of ureter)/seg-mental ureterectomy.

— adrenal gland: present/absent.

— up to one-third of renal cancers are asymptomatic and an incidental finding on radiological examination. The classic triad of flank pain, mass and haematuria is infrequent and usually indicates advanced disease. Weight loss and painless haematuria are perhaps the most frequent presenting complaints. Investigation for renal cell carcinoma is by abdominal ultrasound and CT scan, which can distinguish cystic and solid lesions and provide staging information on nodal, renal vein and inferior vena cava (IVC) involvement. Renal pelvic cancers are defined by retrograde pyelography and ureteropyeloscopy with cyto-logical brushings and/or forceps biopsy. Needle biopsy is only done in a minority of renal cell cancers with extensive spread for the purposes of obtaining a tissue diagnosis as a prequel to palliative adjuvant or immunotherapy, and also to rule out a more treatable cause of the renal mass, e.g. malignant lymphoma. Most imaging-proven and kidney confined mass lesions require surgical resection and omitting an invasive needle biopsy avoids disrupting local anatomical structures and any risk of upstaging tumour. The mainstay of surgical treatment for renal cell carcinoma is radical nephrectomy but advances in preoperative imaging and staging have made partial nephrectomy an option for select patients, e.g. tumour <4cm, tumour in a solitary kidney, or with a poorly functional contralateral kidney. Renal pelvis/ureter carcinoma requires nephrectomy with ureterectomy although endoscopic resection for early low grade lesions is also now being used.

Tumour

Site

— upper/lower pole, midzone, hilum, medullary, cortical, subcapsular, extracapsular, pelvic/peripelvic.

— single/multiple (satellite nodules in 5% of renal cell cancers) or bilateral (1%).

— most renal cell carcinomas are centred on the cortex, transitional cell carcinomas on the pelvis.

Size

— length x width x depth (cm) or maximum dimension (cm).

Appearance

— cystic/solid/lobulated: renal cell carcinoma.

— necrotic/haemorrhagic/yellow: renal cell carcinoma.

— circumscribed/tan/central scar: oncocytoma and chromophobe/papil-lary carcinomas.

— white/granular/scirrhous: sarcomatoid and collecting duct carcinomas.

— papillary/sessile/scirrhous: renal pelvis carcinoma.

Edge

— circumscribed/irregular.

Compression/infiltration structures

— perinephric fat, capsule, cortex, medulla, pelvis, peripelvicalyceal fat (renal sinus), adrenal gland, renal vein.

2. HISTOLOGICAL TYPE

Renal malignancy of childhood is not discussed.

Renal cell carcinoma (Heidelberg/WHO classifications)

Adenocarcinoma

— clear cell: 70% of cases. Solid/trabecular/alveolar/tubuloacinar/cystic patterns with a prominent sinusoidal vascular stroma and areas of haemorrhage. Glycogen and fat-rich clear to eosinophilic granular cytoplasm and variable nuclear morphology.

— papillary: 10-15% of cases. Potentially multifocal, bilateral and familial arising on a background of precursor papillary adenoma(s). Formerly termed chromophil carcinoma. Encapsulated, with solid and tubular patterns but at least 50-70% of the tumour area is papillary with stromal aggregates of foam cells, focal psammomatous microcalcification and haemorrhage. The commonest renal carcinoma in dialysis patients.

type 1—basophilic cuboidal cell, uniform bland appearance and more often multifocal type 2—eosinophilic columnar cell with nuclear (pseudo) stratification.

— chromophobe: 3-5% of cases. Solid and nested patterns with a perinuclear halo, clear to flocculent cytoplasm (positive with Hale's colloidal iron and alcian blue), prominent ("koilocyte-like") cytoplasmic membranes and "wrinkled" hyperchromatic nuclei.

— collecting duct: 1% of cases, located in the medulla with irregular tubules and papillae in a desmoplastic stroma, hob-nail cells and nuclear stratification. Aggressive although a rare low-grade variant exists.

— sarcomatoid: 1-2% of cases with a solid/scirrhous appearance and fibrosarcomatous/MFH-like spindle cell (± giant cell) morphology and usually with high nuclear grade. May occur either as a major or minor component with the other main subtypes, and also renal pelvic carcinoma, and is regarded as an indication of disease progression and a poorly differentiated or high-grade form of them with poor prognosis rather than a specific entity in its own right. Pale/scirrhous area within an otherwise usual renal cell carcinoma should be preferentially sampled for histology. Infiltrating transitional cell carcinoma of the renal pelvis has a similar appearance.

— mixed: about 10% of cases show mixed differentiation.

— unclassified: 5-10% of cases do not fit into any distinctive category.

— on a spectrum with and forming a differential diagnosis for the eosinophilic variants of well-differentiated (grade 1) renal cell carcinoma and chromophobe carcinoma is benign renal oncocytoma. A circumscribed, tan/brown lesion with a central radial scar comprising sheets, tubules and small nests of cells, with abundant eosinophilic cytoplasm and a central, small round nucleus, set in a variably oedematous stroma. Forming 3-5% of renal neoplasms, its cytoplasm is rich in mitochondria. It is excluded in favour of a designation of renal cell carcinoma by necrosis, mitoses, clear cells, spindle cells, papillary areas, gross vascular invasion or gross extension into perirenal fat. It is occasionally multifocal and bilateral with associated oncocytomatosis.

Neuroendocrine carcinoma

— carcinoid/small cell/large cell: rare.

— NSE, chromogranin/synaptophysin/CD56 positive.

— small cell carcinoma may also arise from the pelvic mucosa as part of a transitional cell carcinoma secondarily involving the kidney parenchyma.

Renal pelvis/ureter carcinoma

Transitional cell (urothelial) carcinoma

— ± calculi or a history of analgaesic nephropathy with renal papillary necrosis.

— single/multifocal.

— 20% of upper renal tract neoplasms.

— 30% of cases are low grade and papillary giving hydroureter/ hydronephrosis with a non-functioning kidney and a radiological filling defect in the pelvis/ureter. The other 70% of cases are high grade and a mixture of papillary and sessile lesions. The latter can infiltrate the medulla and cortex with a scirrhous gross appearance and squamoid or spindle cell morphology.

Squamous cell carcinoma

— calculi/infection/squamous metaplasia of the pelvic mucosa.

— mostly high-grade and locally advanced/metastatic at presentation.

Prognosis is poor.

— mixed: as part of a high-grade transitional cell carcinoma (40% of cases).

Adenocarcinoma

— pure: tubulovillous/mucinous/signet ring cell/papillary non-mucinous. Adjacent pyelitis cystica/glandularis secondary to chronic inflammation, e.g. calculi.

— mixed: as part of a high-grade transitional cell carcinoma.

Sarcomatoid carcinoma

— spindle cell carcinoma with high nuclear grade and cytokeratin positive. May be combined with foci of usual transitional cell carcinoma.

Metastatic carcinoma

— direct spread: cervix, prostate, bladder (distal ureter), gut, retroperi-toneal metastases, e.g. lung and breast.

— distant spread: lung, malignant melanoma (skin), breast, stomach, pancreas, ovary, testis.

3. DIFFERENTIATION/GRADE

Renal cell carcinoma

Well/moderate/poor/undifferentiated, or Grade 1/2/3/4. Differentiation and nuclear grade are not infrequently heterogeneous within a lesion. The malignant cell typically has a low nuclear/cyto-plasmic ratio.

Nuclear grade (Fuhrman)

1. Round, uniform, 10 |m, nucleoli absent

2. Slightly irregular, 15 |m, nucleoli visible

3. Moderately to markedly irregular, 20 |m, large nucleoli

4. Bizarre multinucleated forms, >20|m, prominent nucleoli, clumped chromatin.

Grades 2 (35%) and 3 (35%) account for the majority of cases. Prognostic significance of nuclear grade also varies according to tumour type, e.g. metastatic papillary renal carcinoma is usually high-grade whereas metastatic clear cell renal carcinoma is often of low nuclear grade.

Transitional cell carcinoma

For further discussion of classification of urothelial neoplasms see Chapter 30.

For non-transitional pelviureteric cancers: well/moderate/poor/undiffer-entiated, or Grade 1/2/3/4.

4. EXTENT OF LOCAL TUMOUR SPREAD

Border: pushing/infiltrative. Lymphocytic reaction: prominent/sparse.

Capsule, perirenal fat

The capsule is often elevated and compressed by the pushing and lobu-lated margin of renal cell adenocarcinoma and this must be distinguished from actual histologically proven invasion of perirenal fat by tumour cells (pT3a). In this respect the capsule and fat should not be stripped from the kidney prior to sectioning it, otherwise the cortex/capsule/fat interface is lost. Extension to the renal sinus (peripelvicalyceal fat) should be actively examined for, as it is particularly susceptible to vascular invasion.

Pelvis, ureter

Renal pelvic transitional cell carcinoma is not infrequently multifocal (40%) with concurrent ureteric lesions ± bladder tumour. The adjacent urothelium is often abnormal, ranging from hyperplasia through dysplasia to carcinoma in situ.

Renal vein

Renal cell adenocarcinoma has a propensity for venous invasion, and involvement of the renal vein or its segmental (muscle containing) branches should be identified grossly at specimen dissection with subsequent histological confirmation.

The TNM classification applies to renal cell, renal pelvis and ureter carcinomas.

Renal cell carcinoma pT1 tumour < 7 cm in greatest dimension, limited to the kidney a. <4cm b. 4 cm < tumour <7 cm pT2 tumour > 7 cm in greatest dimension, limited to the kidney pT3 tumour invades:

a. perinephric fat* or adrenal gland1

^Includes renal sinus (peripelvicalyceal fat) and Mirect invasion of the ipsilateral adrenal gland. Contralateral adrenal gland involvement is rare (pM1). Gerota's (renal) fascia is retrorenal and prerenal with invasion beyond the latter sometimes resulting in peritoneal involvement (pT4). Renal sinus involvement has been noted to be the commonest site of extrarenal extension (pT3) and vascular involvement, and correlates with tumour type, grade and size. Its evaluation, which has been frequently omitted in the past, can upstage disease if involved.

Adrenal gland pTI = < l cm dia, confined to kidney

Adrenal gland

pT2 = > l cm dia, confined to kidney pTI = < l cm dia, confined to kidney pT2 = > l cm dia, confined to kidney

Fascia

Perirenal fat

Fascia

Perirenal fat

pT3a = into adrenal gland or perirenal fat pT3b = into renal vein or IVC below diaphragm pT3c = into IVC above diaphragm D = tumour distance (mm) to the Circumferential Radial Margin (CRM) of excision of perinephric fat pT4 = beyond Gerota's fascia, into abdominal wall or adjacent organs

Figure 29.1. Renal cell carcinoma. |QÂ|

b. grossly into renal vein, IVC or its wall below diaphragm c. grossly into IVC or its wall above diaphragm pT4 tumour invades beyond Gerota's fascia.

Involvement of renal vein and ipsilateral adrenal gland is seen in 10% and 5% of cases, respectively. Metastases occur in the lung, skeleton and skin and to almost any site where they can mimic primary clear cell tumour in the involved organ, e.g. thyroid, ovary. Preferential metastatic sites are seen with various subtypes of carcinoma, e.g. papillary carcinoma has fewer lung metastases and more lymph node deposits than clear cell carcinoma, and chromophobe carcinoma tends to spread to liver.

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