8. Renal neoplasms

Question 1

Types of renal neoplasm

Answer 1

1. Angiomyolipoma
2. Oncocytoma
3. Renal Cell Carcinoma
4. Nephroblastoma (Wilms Tumour)
5. Urothelial (Transitional Cell) Carcinoma

Question 2

Definition of angiomyolipoma

Answer 2

Most common benign mesenchymal tumour of the kidney

Question 3

Epidemiology & associations with angiomyolipoma

Answer 3

1. Belongs to the family of PEComas (tumours containing perivascular epithelioid cells) which includes:
   - Lymphangioleiomyomatosis
   - Clear cell sugar tumour of the lung, pancreas, uterus
   - Cardiac rhabdomyomas
2. Occurs at all ages, but typically resected at age 40 or older
3. Most commonly found in kidneys, but can also occur in:
   - Liver
   - Retroperitoneum
   - Lungs

Question 4

Pathogenesis of angiomyolipoma

Answer 4

1. Sporadic
2. Familial: associated with tuberous sclerosis
   - Loss of function mutations of TSC1 or TSC2 tumour suppressor genes
   - Characterized by cerebral cortical lesions (producing epilepsy & mental retardation), skin abnormalities & unusual benign tumours (e.g. cardiac tumours)

Question 5

Morphology of angiomyolipoma

Answer 5

1. Grossly:
   - Unencapsulated
   - Variegated cut surface with yellow fatty areas
2. Histologically:
   - Mixture of myoid spindle cells, epithelioid cells, adipocytes & blood vessels (often thick walled)
   - Myoid cells show immunostaining for HMB-45

Question 6

Clinical features of angiomyolipoma

Answer 6

1. Can be accurately diagnosed on CT scan due to its large fat content (appears radiolucent)
2. May rupture & bleed

Question 7

Definition of oncocytoma

Answer 7

Benign tumour arising from intercalated cells of the collecting tubule

Question 8

Morphology of oncocytoma

Answer 8

1. Grossly:
   - Tan, mahogany brown mass
   - Well-encapsulated, can reach up to 12cm
2. Histologically:
   - Tumour cells large, round, eosinophilic
   - Benign looking nuclei with large nucleoli

Question 9

Definition of renal cell carcinoma

Answer 9

Malignant tumour arising from the renal tubular epithelium

Question 10

Epidemiology of renal cell carcinoma

Answer 10

1. Accounts for 85% of malignant renal tumours in adults
2. Mostly occurs in the 6th & 7th decades of life
3. Male : female = 2 : 1

Question 11

Types of renal cell carcinoma

Answer 11

1. Clear cell carcinoma (70-80%)
2. Papillary carcinoma (10-15%)
3. Chromophobe carcinoma (5%)
4. Collecting duct carcinoma (<1%)

Question 12

Clear cell carcinoma (70-80%)

Answer 12

Arises from the proximal tubules

Question 13

Pathogenesis of clear cell carcinoma

Answer 13

1. Sporadic
2. Familial: von Hippel Lindau syndrome
   - loss of sequences on short arm of chromosome 3 → leading to mutations of the VHL gene (a tumour suppressor gene that encodes part of a ubiquitin ligase complex vital for the degradation of hypoxia-inducible factor 1)
   - associated with pheochromocytoma, hemangioblastomas of cerebellum & retina & cysts involving the liver, kidneys & pancreas

Question 14

Morphology of renal cell carcinoma (clear cell type)

Answer 14

1. [Grossly]
   - Solitary, unilateral mass
   - Circumscribed appearance
   - Yellowish cut surface with foci of necrosis & hemorrhage
   - Invasion of renal vein (can grow as a continuous tumour cord into right heart)
   - Tendency to metastasize widely even before any local symptoms
2. [Histologically]
   - Polygonal cells with clear cytoplasm arranged in tubular or trabecular architecture
   - Delicate branching vasculature
   - Invasion of renal vein or its branches may be seen

Question 15

Papillary carcinoma

Answer 15

Arises from the distal tubules

Question 16

Pathogenesis of papillary carcinoma

Answer 16

MET oncogene

Question 17

Morphology of papillary carcinoma

Answer 17

1. Can be multifocal & bilateral
2. Cystic & hemorrhagic
3. Cuboidal/columnar cells lining papillae
4. Foam cells, psammoma bodies in papillary core

Question 18

Chromophobe carcinoma

Answer 18

Arises from the intercalated cells of collecting tubule

Question 19

Prognosis of chromophobe carcinoma

Answer 19

Excellent

Question 20

Morphology of chromophobe carcinoma

Answer 20

1. Pale eosinophilic cells with perinuclear halo
2. Arranged in solid sheets
3. Largest cells are concentrated around vessels

Question 21

Collecting duct carcinoma

Answer 21

Arises from the collecting ducts

Question 22

Morphology of collecting duct carcinoma

Answer 22

Irregular channels lined by highly atypical epithelium with a hobnail pattern

Question 23

Clinical features of renal cell carcinoma

Answer 23

1. Painless hematuria
2. Mass in flank
3. Fever (due to necrosis)
4. Costovertebral pain
5. Paraneoplastic syndromes (polycythaemia, hypertension, hypercalcemia, Cushing syndrome, amyloidosis etc)

Question 24

Definition of nephroblastoma (Wilm’s tumour)

Answer 24

Paediatric renal tumour

Question 25

Epidemiology & associations with nephroblastoma (Wilm's tumour)

Answer 25

1. Usually diagnosed between ages 2 & 5 2. Associated with congenital malformation syndromes: - WAGR syndrome - Denys-Drash syndrome - Beckwith-Wiedemann syndrome

Question 26

Morphology of nephroblastoma (Wilm's tumour)

Answer 26

1. Grossly: - Well circumscribed grayish soft mass - Foci of hemorrhage, cysts & necrosis - Begins in renal cortex & eventually replaces kidney 2. Histologically: - Sheets of small blue cells (blastemal component) - Abortive tubular & glomeruloid structures (epithelial component) - Spindle shaped cells (stromal component) - Heterologous elements such as striated/smooth muscle & cartilage may also be found

Question 27

Clinical features of nephroblastoma (wilm's tumour)

Answer 27

1. Signs & symptoms: - Large abdominal mass i. Usually unilateral, bilateral in 10-15% of cases ii. May cause intestinal obstruction - Hematuria - Fever 2. Metastases: - Hematogenous & lymphatic spread to lungs, liver, brain & lymph nodes 3. Treatment: - Combination nephrectomy & chemotherapy - Generally good prognosis even for tumours which have spread beyond the kidney

Question 28

Definition of Urothelial (Transitional Cell) Carcinoma

Answer 28

Neoplasm arising from the urothelium (transitional cell epithelium) lining the renal calyces, pelvis, ureter & bladder

Question 29

Types of urothelial carcinoma

Answer 29

1. Papillary urothelial carcinoma (non-invasive) | 2 Invasive urothelial carcinoma

Question 30

Morphology of urothelial carcinoma

Answer 30

1. Identical to urothelial carcinoma of the bladder 2. Exophytic mass growing from the surface of the areas lined by urothelium (renal calyces & pelvis) 3. Usually associated with urothelial carcinoma of the ureter & bladder

Question 31

Clinical features of urothelial carcinoma

Answer 31

Usually discovered early 1. Fragmentation gives rise to noticeable hematuria 2. Blockage of urinary outflow gives rise to hydronephrosis & flank pain