Urinary: Renal Masses Flashcards
What is considered “enhancing” for a renal mass?
An increase of at least 15 HU
Note: Increase of 10 HU or less is within technical limits (pseudoenhancement).
What type of bone metastases occur in renal cell carcinoma?
Lytic (always)
Enhancing renal mass…
RCC until proven otherwise
Renal mass containing calcifications and macroscopic fat…
RCC until proven otherwise
Note: Angiomyolipomas should never have calcifications.
What are the major subtypes of renal cell carcinoma?
- Clear cell (most common)
- Papillary
- Medullary
- Chromophobe
- Translocation (most common in kids)
Which renal cell carcinoma subtype is associated with Von Hippel Lindau?
Clear cell
How can you differentiate clear cell from papillary renal cell carcinoma on imaging?
Clear cell will enhance equal to cortex on the corticomedullary phase
Papillary is less vascular and will be darker than cortex on the corticomedullary phase
Differential for a T2 dark renal mass
- Papillary RCC
- Lipid-poor angiomyolipoma
- Hemorrhagic cyst
What is the most common RCC subtype in a transplanted kidney?
Papillary
Note: Transplanted kidneys have a 6x greater risk of primary renal malignancy.
Which RCC subtype is more aggressive: clear cell or papillary?
Clear cell is more aggressive
Which RCC subtype is associated with sickle cell trait?
Medullary
Medullary RCC is more common in what pt population?
Younger pts (especially with sickle cell trait)
Note: This is a highly aggressive tumor and has usually metastasized by the time of diagnosis.
Which RCC subtype is associated with Birt Hogg Dube?
Chromophobe
What is the most common RCC subtype?
Clear cell
What is the most common RCC subtype in children?
Translocation
Which RCC subtype is associated with a history of prior cytotoxic chemotherapy?
Translocation
Stage 1 RCC
<7 cm and limited to the kidney
Stage 2 RCC
> 7 cm, but limited to the kidney
Stage 3 RCC
Still limited by Gerota’s fascia, but:
- Renal vein invasion
- IVC invasion
Stage 4 RCC
Extension beyond Gerota’s fascia OR involving the ipsilateral adrenal gland
What is the most common metastatic tumor to invade/infiltrate the kidney?
Renal lymphoma
Classic imaging appearance of renal lymphoma
Bilaterally enlarged kidneys with small, hypodense cortically-based solid nodules/masses and associated lymphadenopathy
Note: Renal lymphoma can pretty much look like anything and is a solitary mass 25% of the time.
Think renal lymphoma
Note: Bilateral bulky kidneys.
What is the most common visceral organ involved in leukemia?
The kidneys
What is the most common benign tumor of the kidney?
Angiomyolipoma
Angiomyolipomas are associated with…
Tuberous sclerosis
Complications of angiomyolipomas
Hemorrhage (if they get large enough, generally >4 cm)
Note: Hemorrhage seems to be more common in pregnancy.
Angiomyolipoma with calcifications…
Does not happen, be worried about RCC
Which RCC subtype is most likely to have macroscopic fat?
Clear cell
What percentage of angiomyolipomas are lipid-poor?
5%
Note: These are best identified on MRI for being T2 dark.
What is the best way to diagnose a lipid poor angiomyolipoma
MRI showing that it is T2 dark
Note: Signal dropout between in and out of phase images (microscopic fat) is more common in clear cell RCC than lipid-poor AMLs.
What is the second most common benign renal tumor?
Oncocytoma
What is the classic imaging feature of an oncocytoma on CT/MRI?
Central scar
What is the classic imaging feature of an oncocytoma on ultrasound?
“spoke wheel” vascular pattern
What is the classic imaging appearance of an oncocytoma on PET imaging?
The oncocytoma will be hotter than the surrounding renal cortex
Note: RCCs are usually colder than renal cortex.
Treatment for oncocytoma
Usually surgical excision (must be treated as RCC because there is no way to differentiate on imaging alone)
Note: Even on biopsy, both can have oncocytic features.
Renal mass with a central scar…
Most likely to be an oncocytoma; however, RCCs can have a central scar also (so these are almost always surgically resected)
Note: If you are highly suspecting oncocytoma (e.g. mass if hotter than cortex on PET), then they may chose to do a renal-sparing partial nephrectomy rather than a total nephrectomy.
What syndrome is associated with bilateral renal oncocytomas?
Birt-Hogg-Dube syndrome
Think multilocular cystic nephroma
Note: Characterized by an absence of solid component or necrosis.
Multicystic renal lesion that protrudes into the renal pelvis…
Multilocular cystic nephroma
Which part of the pancreas is not retroperitoneal?
The tail
Is the rectum a retroperitoneal structure?
The upper 2/3 is retroperitoneal, the lower 1/3 is subperitoneal
What percentage of nonvisceral primary retroperitoneal neoplasms are malignant?
75%
Note: This is why retroperitoneal masses are highly suspicious.
Incomplete bladder emptying
Retroperitoneal lipomatosis (overgrowth of benign fat that classically pushes the bladder anteriorly)
What is the most common nonvisceral primary malignancy of the retroperitoneum?
Liposarcoma
Does liposarcoma have a high recurrence rate?
Yes (67%)
Fat-containing retroperitoneal mass…
Think liposarcoma
Note: Do not call fat containing lesions in the retroperitoneum lipomas, even if small and simple-appearing. Always be concerned about liposarcomas in the retroperitoneum.
Massive fat-containing lesion in the retroperitoneum that may or may nor arise from the kidney and has calcifications…
Think liposarcoma
Note: If you are confident it originated from the kidney, then be concerned about RCC.
Heterogeneous, enhancing mass in the retroperitoneum with adjacent osseous erosion in a pediatric pt…
Think rhabdomyosarcoma (most common soft tissue sarcoma in children)
Think retroperitoneal liposarcoma
Note: Fat containing retroperitoneal mass.
Pediatric pt
Think rhabdomyosarcoma
Retroperitoneal soft tissue masses in a pt with myelofibrosis…
Think extra-medullary hepatopoiesis
What history should make you think of possible extra-medullary hematopoiesis when you see retroperitoneal soft tissue masses?
- Hemoglobinopathies (e.g. sickle cell, thalassemia, spherocytosis, etc.)
- Myelofibrosis
- Leukemia
What is the most common retroperitoneal malignancy?
Lymphoma
Classic imaging appearance of retroperitoneal lymphoma (Hodgkin and non-Hodgkin)
non-Hodgkin: Larger, non-continuous retroperitoneal masses involving the mesentery
Hodgkin: Smaller, more continuous retroperitoneal nodules involving the para-aortic region
Best imaging study for retroperitoneal lymphoma
PET/CT
Most common cause of retroperitoneal hemorrhage
Over-anticoagulation (elevated PT/INR)
Common causes of retroperitoneal hemorrhage
- Over-anticoagulation (most common)
- Aortic leak/rupture (second most common)
- Bleeding RCC or angiomyolipoma
Differential for mantle-like soft tissue mass around the aorta
- Lymphoma (can dispose aorta anteriorly)
- Retroperitoneal fibrosis (rarely seen above the renal arteries, tends to obstruct things)
- Erdheim Chester (consider if also shown radiographs of the legs with bilateral symmetric sclerosis of the metaphyses)
Can PET/CT help distinguish lymphoma from retroperitoneal fibrosis?
Not really, both can be hot on PET
Is retroperitoneal fibrosis or lymphoma more likely to cause ureteral obstruction?
Retroperitoneal fibrosis is more likely to cause obstructions
Note: Retroperitoneal lymphoma is more likely to push things than obstruct them.