Pediatric Renal Tumors: Usual and Unusual - HD

Introduction

My name is Dr. Carol Bar Dewald. I've been a pediatric radiologist at Children's Hospital in Boston for almost 25 years.

It's my passion ultrasound in particular, and I'll be speaking about pediatric renal tumors, the usual and unusual.

I have no disclosures.

Objectives

The objectives are below to describe the spectrum of common and uncommon fetal neonatal and pediatric renal masses, which are very different from those seen in adults.

And we'll give some age specific clues, tricks of the trade and pitfalls in the diagnosis of pediatric renal masses with sonography.

We'll focus a little bit on what the referring physician or surgeon needs to know.

We'll talk about mimics and pitfalls of renal masses and we'll divide things into some basic age groups, fetal neonatal, pediatric, the older group, and then adolescent and young adults.

And we'll speak in a little bit more detail about each of these subtopics.

Neph, neuroblastoma, ptosis, mesoblast, nephroma in the fetal neonatal group, multilocular cystic renal tumor and pediatric renal masses.

Wilms tumor, clear cell sarcoma of the kidney, which is different roid tumor.

And then in the older group, renal cell carcinoma.

Yes, it does sometimes happen in pediatrics.

Medullary carcinoma of the kidney.

Renal angiomyolipoma, renal lymphoma.

And a brief comment about metastases.

Normal Renal Findings

We do have some pictures of renal, loation.

A diagram on the right here shows the normal lumpy contour in a diagrammatic form and in a photograph you can see a path specimen.

And then on a fetal, actually neonatal MRI at about six months of life the same normal undulation.

This is a normal finding.

What the Radiologist Needs to Know

So what does the radiologist need to do know?

Is this a neoplasm? How certain are we?

Is it on one or both sides?

We need to talk about the, imaging characteristics.

Is it solid cystic, mixed fatty calcified?

Is the mask confined to one kidney?

Is there venous extension into the renal vein or IVC?

Are there distant metastases?

Are any other imaging studies needed?

And what is the best imaging strategy for monitoring?

Mimickers of Renal Masses

So this slide shows some examples of mimickers of bad so-called renal masses.

So on the left is a one month old baby where you can see normal fetal loation.

As we saw in those, pathology specimens on the prior slide, the contour has some lumps.

There's a hypoechoic medullary pyramid, not a mass or dilated calyx.

This is a perfectly normal one month old.

The middle example is a six month old who presented with fussiness.

And as part of the workup, a renal ultrasound was performed.

And you can see that in the upper pole there's an epigenic, fairly well-defined mass like structure that has a little, a few little blips of color flow on it, but is perfused in a different pattern than the rest of the kidney.

And this, as it turns out, was initially thought to represent a focal neoplasm and was actually biopsied and proved to be pylon nephritis.

So, infection can certainly mimic a mass.

And then on the right is an 8-year-old, patient who had a focal area of swelling in the medial aspect of the upper pole of the right kidney.

Also had a little bit of vascularity.

This was not, biopsied because the patient had signs of infection.

And sure enough, with treatment for pilo, this resolved over time and the contour of the kidney was restored after antibiotics.

So certainly infection can mimic a renal tumor.

And of course, cystic dysplasia as can be seen in multicystic dysplastic kidney or an obstructive neuropathy, nephropathy can cause findings that mimic malignant masses.

And we'll talk a little bit later about some of these syndromes where screening for tumors is recommended.

Cysts and Multicystic Dysplastic Kidney

So back to mimickers, specifically cysts.

Those of you who do pediatric radiology know about the condition of multicystic dysplastic kidney, which is thought to occur because of a very tight obstruction during fetal development.

And you end up with a kidney most often.

That is comprised of multiple cysts of varying size.

As you can see in this pathologic specimen and diagram, remember that MCDK can involve just part of the kidney, and if that's the case, it might mimic a renal cystic mass.

The example on your left shows a very complex looking cyst compressing the left kidney.

This was observed in a seven week old baby boy who presented with abdominal distension and a palpable mass on physical exam.

He did go on to have some additional cross-sectional imaging, but if you ask me as a sonographer, this told us nothing more about what the patient actually had.

So it was erroneously thought that this represented a primarily cystic renal tumor.

And as it turns out, this little baby had posterior urethral valves resulting in obstruction upstream, fornace rupture and creation of a perinephric oma, which mimicked a mass.

So remember, not every cystic mass proves to be a neoplasm.

The example on your right is a very interesting case where a patient initially presented as a fetus with the observation of what was called atypical hydronephrosis.

They had an ultrasound soon after delivery and there was a septated cyst observed in the lower pole of the kidney, not hydronephrosis.

This was thought to be a little bit unusual and was followed, over time at about six months with another ultrasound.

And at this point it seemed as though there was a solid component.

We went on to additional cross-sectional imaging and saw this flame like enhancing soft tissue.

And sure enough, this proved to be a cystic wilms tumor, so indeed a neoplasm.

So be cautious. Not every cyst is a neoplasm, but not every cyst is a simple cyst.

Adrenal vs. Kidney Origin

Alright, it's very important to sort out whether or not the mass you're looking at is actually from the adrenal gland or from the kidney itself.

And while this sounds as though it should be easy, it can be very challenging if the mass is big.

So I've shown some reconstructed CT examples.

On the far left you can see that the kidney is pushed down by a large mass and it's not involving the kidney itself.

Although at a quick glance you might think it was.

The next picture shows a mass in the kidney with a claw sign.

So the edge of the, kidney is wrapped around the tumor itself, clearly showing that it is from, the kidney itself.

So the CT mr and ultrasound findings of a claw sign tell you that the mass is within the kidney proper.

And I love this picture.

It really does look like a crescent moon.

If you compare the two pictures just a little, pearl neuroblastoma, which is almost, invariably originating from the adrenal gland, if it's very large and you're not so sure whether or not it's from the kidney or the adrenal, if you see that the mass is encasing, stretching and lifting the aorta off of the spine, you're almost certainly dealing with a adrenal, origin mass, not a wilms tumor, but a neuroblastoma as in this case talking more specifically about additional tumors.

Newborn Classification

Congenital Mesoblastic Nephroma

Alright, so we're getting into the newborn classification.

The first topic is congenital meso nephroma.

This is the most common solid tumor of infancy.

The vast majority are diagnosed within the first few months of life.

Nonetheless, it's still a very rare tumor comprising only three to six of renal tumors in childhood.

This can be seen prenatally.

And that is becoming more and more common as our probes are becoming, better and better.

This is also sometimes referred to as a fetal fetal renal hematoma.

And the cross section of these tumors really does look like a uterine leiomyoma.

They, contain primarily solid tissue, although occasionally you can see cystic components.

The concentric ring pattern reflects the dilated vasculature.

And in entrapped nephrons, the vessels tend to be displaced, but not invaded.

You can get foci of necrosis, seromas cysts and hemorrhage sometimes, but primarily these are solid appearing masses.

As mentioned, these are generally in very young patients, in the neonatal or even prenatal period.

You can see a picture on your right.

This, now baby had the fetal diagnosis of a large solid mass in the abdomen.

This is the mass. You can see it deviating the aorta off to the side and the branch of the, iliac arteries on cross-sectional imaging.

Here is the mass and a claw sign.

Solid classic appearance presenting in the newborn period.

It's thought that the variable enhancement pattern of these tumors is due to, trapped nephrons within the tumor.

And interestingly, you can get a hypercalcemic variant, often called the cellular form, where on the contralateral kidney you may see rather dramatic medullary nephrocalcinosis.

And this is a really good clue for the diagnosis of congenital meso blast nephroma cellular form.

But you do have to be cautious.

These can mimic wils tumor and they're often assumed to be wils tumor.

Multilocular Cystic Renal Tumor

Next topic is multilocular cystic renal tumor.

This is something that tends to happen in boys in infancy and toddlerhood, but it can happen in older patients too.

This tends to be a more cystic mass, unlike the mesoblast nephroma.

These can be partially, partially different.

Also called partially differentiated cystic neph neuroblastoma.

And as you can see in the example here, they don't, they may present rather smaller with some cystic components here on ultrasound T two bright on MRI and only the septi enhance after gadolinium in these coronal pictures.

This is not familial.

It is sporadically associated with other congenital anomalies.

Sometimes it's termed a cystic nephroma and if you have cystic wilms, you can have cystic wilms tumor within it.

So this should be considered a spectrum.

Another example of multilocular cystic renal tumor, maybe a little bit bigger in an older patient, primarily cystic.

With septations, you really don't get much, doppler flow within the septi.

Classically, you may have some calcifications and you do have a little bit of septal enhancement here on this example by MRI, so remember primarily cystic and unfortunately there is sometimes a malignant component.

So these generally RX sized.

Nephroblastomatosis Complex

Next topic, neph neuroblastoma ptosis complex.

So a nephrogenic rest as seen in this pathology histology slide here is rynal renal tissue that persists beyond the 36 week of fetal life.

And if you have multiple nephrogenic rest, it's called neph neuroblastoma ptosis, you can have intra and peri lobar forms of nephrogenic rest.

Although the distinction is sometimes very difficult to make just by imaging for the intra lobar form, there are associations with sporadic ayia with a fairly high Wilms tumor risk DR syndrome, which includes male pseudo herma and nephropathy wager syndrome, which is an acronym for Wilms Ayia Genital anomalies and Mental Retardation.

And for the peri lobar foam form, there is, association with Hemi hypertrophy Beckwith Weideman, which includes macroglossia, macrosomian, and Emale.

A diagnosis that can be made prenatally perelman syndrome and trisomy 18.

So the example here on your right is a baby or a child who'd had their right kidney excised for Wilms tumor.

And we knew the left kidney was at risk of developing a secondary tumor.

And sure enough there's a tiny little nephrogenic rest that required following over time.

Happily, this did not develop into a wilms tumor.

Neph oblasts ptosis complex is when you get really large bilateral neph neuroblastomas as in this example as seen by ultrasound, where the lesions themselves look homogeneous without normal cortico medullary differentiation.

And the same observation is seen here on a coronal reformat reformatted ct.

So it is important, to perform surveillance, imaging to detect Wilms tumor in patients with this condition.

It's a little controversial how this should be done.

The National Wilms Tumor Study recommends an ultrasound every three to four months until age eight when the risk of wils tumor is thought to decrease.

Oh, so the signal intensity of neph, neuroblastoma ptosis on MR is homogeneous.

Whereas Wilms tumor tend to have a more heterogeneous appearance.

Pitfalls here, normal fetal loation may mimic masses.

A column of brittan may make, may mimic a mass and collecting system.

Duplications can have divisions of the cortex of the kidney that mimic, neph neuroblastomas.

So you really do need to use high resolution ultrasound probes.

Pediatric Renal Masses

Wilms Tumor

Wilms tumor is the most common abdominal malignancy of childhood and comprises 87% of pediatric renal masses.

The peak incidence occurs at age three to four years with the vast majority occurring before age five years.

And again, they're rare in neonates.

They tend to per, present as palpable masses.

Abdominal pain, hematuria.

Occasionally you'll, see hypertension and you, can see again there are some associations such as Dr. Wager and Beckwith Weidemann syndrome, which are at risk of developing Wilms tumor.

Bilateral Wilms tumor is almost exclusively seen in neph, neuroblastoma, ptosis patients.

And most wilms do arise in the kidney, but there are occasionally extrarenal Wilms tumor.

And the pictures of the two gentlemen here are Beckwith and Wiman, the two who describe this famous condition.

Really an interesting story.

This is an example of a patient who had bilateral nephrogenic rests and sure enough developed in the lower pole of one of the kidneys, a structure that became more and more hetero heterogeneous over time.

This is an intraoperative ultrasound and that did prove to have features of Wilms tumor.

Again, rare neonates.

This tumor can, or tends to extend into the IBC and then into the right atrium.

And this can be seen definitively, definitively with ultrasound as in this picture where a tumor thrombus is being measured within the IBC.

Wilms tumor can contain fluid, fat and calcification, so don't let that dissuade you from the diagnosis.

10% are bilateral.

Not every pediatric renal mass is a wilms tumor, though most are.

I love this particular example.

This little baby came in because their father carried a diagnosis of Wilms tumor and ultimately needed a renal transplant, treated our at our hospital.

I happened to be on duty. An ultrasound baby came in.

Sure enough, the baby was being screened because of the concern for a familial form of Wilms tumor.

There was a mass seen by ultrasound and by ct and this did also prove to be a wils tumor.

Happily, both, father and baby are doing well.

Clear Cell Sarcoma of the Kidney

Next topic, clear cell sarcoma of the kidney. This is worse.

This comprises 5% of all primary renal tumors in childhood.

There's no known familial or syndromic association.

And after 1978, this was classified as a separate entity from Wilms two.

The age range is similar.

There is a male predominance and there are unfortunately no imaging features that are distinct to differentiate clear cell sarcoma from Wilms tumor.

Although they then do tend to have more cystic components.

Negativity to the WT one gene is important.

This is opposite to the condition of wilms tumor and unfortunately there is a predilection for bone metastases.

So you have to look for them, you have to do either bone scintigraphy, or skeletal surveys.

And the example on your right is a rather angry looking renal mass.

We thought it was a wilms tumor, but pathology, proved it to be a clear cell sarcoma.

These also can metastasize to lymph nodes, lung and liver.

As mentioned, these tend to be more cystic and they do have a predilection for bone metastases.

So you need to look here.

There is some subtle increased uptake in the tarsal bones of the foot, and a subtle lucency seen on the radiograph.

This is an interesting example because the tumor itself is occurring in the right side of a horseshoe, kidney as seen on CT and also as documented on the ultrasound.

So really in all honesty, the CT added nothing here.

The ultrasound showed all findings.

Rhabdoid Tumor of the Kidney

Rhabdoid tumor of the kidney.

80% of children with this condition are less than age two years.

This is a little younger than the Wilms tumor Group.

This also has imaging features, that are similar to Wilms tumor.

They commonly present with hematuria due to invasion of the renal pelvis.

They may have a subcapsular hematoma, they may have fever, hypertension and hypercalcemia with cutaneous nodules sometimes termed the blueberry muffin baby.

And I wanted to show you this particular example where the child presented with hypercalcemia and again, a rather striking example of medullary nephrocalcinosis.

So we've seen this now with roid tumor and with meso nephroma.

One is a not such a bad tumor and this one of course is a much more aggressive tumor.

They tend to metastasize early and you may actually observe a CNS primary with metastatic involvement of the kidneys as this unfortunate, 6-year-old had a CNS primary with spread to the kidney.

This has the worst prognosis of all childhood renal tumors.

Here's some additional examples.

Look for signs of renal pelvis invasion, cent.

The mass itself may be central within the kidney as seen on this ultrasound.

You may have some trapping of fluid because the pelvic position creates a hydro, an obstructive type picture.

And here's a, pathology correlate showing the central nature of the tumor renal cell carcinoma.

Older Group: Renal Cell Carcinoma

This is rare in the first two decades of life, but does occasionally occur in the first decade.

Wilms tumor outnumbers RCC by a ratio of 30 to one.

But in the second decade, a solid renal mass is equally likely to be RCC or Wilms tumor.

This comprises 5% of all renal tumors in children with the median age of diagnosis between nine and 12 years.

It is recognized as a second malignancy in children who have been treated for other cancers, particularly neuroblastoma.

And this is a condition where a certain groups of children are at increased risk.

Specifically those with tuberous sclerosis complex and fun Hipple Windau syndrome.

This is a very interesting example from, our own files.

This patient had will, sorry, Williams syndrome with multiple bladder diverticula as this characteristic.

They had an ultrasound of the kidneys as part of their monitoring and they were observed at 26 years, to have this small mass right here.

It it was exophytic and homogeneous and did not have features that told us it was a simple cyst.

They had another, imaging study.

I don't think it added anything particular, but proved to represent renal cell carcinoma.

You can see the stent in this patient who had aortic stenosis in association with their wilms tumor.

So we have a, a little group of patients like this and although the literature doesn't say so, I wonder if we should add William syndrome to the group of children at increased risk for RCC.

80% of these children with this condition have the papillary form, and it's really controversial as to the role of lymph node dissection in these patients.

While lymph node spread decreases survival, it does not do so to the same extent, in, at least in the short term as that of adults with a condition.

Another example of renal cell, carcinoma.

This happens to be in an unfortunate 6-year-old here.

And here's an example of a 10-year-old who'd had a renal transplant for FSG and they were having routine monitoring of the transplant.

Here you can see a little exophytic nodule on ultrasound on MRI and that proved to be a renal cell carcinoma.

So compared to to William's tumor, RCC is more likely to have metastasis.

The masses can be infiltrative, you can have hemorrhage, calcification, cystic degeneration enhancement compared to the adjacent kidney is less.

It invades locally and spreads to retroperitoneal lymph nodes.

It can metastasize to lungs, bones, liver, and brain.

And, 20% of these patients will have metastasis at diagnosis.

The a specific, translocation, the XP 11 translocation patients with this form of RCC can metastasize very late after treatment, sometimes even 20 to 30 years later.

So this should be remembered.

Medullary Carcinoma of the Kidney

Another distinct form of renal tumor in children is the medullary carcinoma of the kidney.

This is highly aggressive.

It is almost exclusively seen in patients of African descent with sickle cell trait or hemoglobin SC disease.

It is thought to arise in the CAE epithelium.

A common region of papillary necrosis in this population tends to present at about age 20, but with a wide range.

In patients younger than 25 years, there's a male female ratio three to one and unfortunately there's a very poor response to any form of treatment.

And the mean survival after diagnosis is really only 15 weeks.

And this is an example of a very sad situation where you can see the heterogeneous mass clearly on the ultrasound.

It doesn't really deform the contour of the kidney itself very well.

Here's the CT correlate already.

There's retroperitoneal adenopathy and this patient died very shortly after diagnosis.

This can spread by, lymphatic lip lymphatic spread as can be seen on this pet ct.

It's really all over the place, including the lungs at this point.

A terrible prognosis.

They, invade centrally.

You'll often end up with peripheral ectasis.

The kidney will enlarge but still maintain its reinform shape.

You make it intratumoral hemorrhage and extensive necrosis in this very aggressive tumor.

Renal Angiomyolipoma

Different topic, renal angiomyolipoma or a ML.

These are disordered arrangements of vascular smooth muscle and fatty elements.

The histology suggests that these are, hematoma, but they are currently formally classified as a true neoplasm.

AMLs are very rare in children in the absence of tuberous sclerosis and in ts specifically AMLs tend to develop by age 10 or so.

This condition is also associated with neurofibromatosis and fun hippo lindo syndrome, but really more in the adult ages.

And if larger than four centimeters approximately, they're known to be susceptible to spontaneous hemorrhage.

The winter lich syndrome is the severe, severe retroperitoneal hemorrhage in this situation.

And you can see in this particular patient by ultrasound a more focal mass and then maybe, an echogenic focus here.

These are presumed to represent multiple angio lipomas in this patient with Ts and you can see there are cysts as well.

Again, this is almost exclusively in TS patients, variable imaging.

They have a variable imaging appearance depending on histologic contents by ct and MR if you see fat really that's diagnostic.

But remember that Wilms and RCC can contain fat, lesions tend to be bilateral in children with Ts.

And the ultrasound on your right here shows a very classic spoke like configuration of an echogenic area, which represents a tiny A ML.

They tend to be perpendicular to the renal cortex.

Renal Lymphoma

Renal lymphoma is rare.

Generally you get this condition as hematogenous spread or extension from retroperitoneal sites.

The kidney does not normally contain lymphoid tissue.

So a primary renal lymphoma is very rare.

If you see a renal lymphoma in children, it tends to be, a Burke lymphoma with multifocal masses within the kidney as here, this is something that's treated with chemotherapy.

So you generally don't have pathologic specimens.

So I've shown you an example from a llama, imaging clues.

These tend to be multiple homogeneous parentable masses that distort but don't invade the collecting system less commonly.

But sometimes they can simply occur as an infiltrative mass, or with enlargement of the kidney itself.

They tend to be hypoechoic on ultrasound with through transmission of sound because they have such a homogeneous, cellular nature and they can present just as big kidneys due to diffuse tumor, infiltration as the only imaging finding.

So remember to consider this possibility.

Key Points

We're wrapping it up here with a few key points.

So let's see. Talking about the newborn, child congenital meso nephroma, a solid neoplasm seen almost exclusively in the neonatal period with variable enhancement.

And those little stars are to remind me to say occasionally you can see medullary nephrocalcinosis and know that you're dealing with the cellular form of meso blast nephroma multilocular cystic renal tumor in a little bit older group containing cysts with septations neph.

Neuroblastoma ptosis may evolve into wilms tumor.

So requires monitoring in Wilms tumor.

You need to look for venous invasion.

And remember that 10% are bilateral wilms tumor may contain soft tissue, fluid fat in calcification.

So don't let the presence of fat in calcification dissuade you from the diagnosis.

Clear cell sarcoma has mentioning features which are very similar to Wilms and clear cell Sarcoma has a predilection for bone metastases, so you need to look for them.

Rhabdoid tumor has the worst prognosis of all childhood renal tumors and is associated with primary or metastatic brain lesions.

This is the second condition where the kidneys might also show, evidence for medullary nephrocalcinosis in the hypercalcemic forms.

Renal cell carcinoma is rare in children in adolescents, but does occur.

RCC may actually be a second malignancy in children with other cancers, particularly neuroblastoma.

RCC in children behaves differently than it does in adults, both in biology and behavior.

Pediatric A ML occurs almost exclusively in patients with tuberous sclerosis.

Medullary carcinoma of the kidney is an aggressive tumor, almost exclusively seen in patients of a African descent with SC trait or SC disease.

Renal cell lymphoma is rare but occurs and can be seen as generally enlarged kidneys or multiple homogeneous masses, often with adenopathy, but it is a rare condition.

Acknowledgment

So I thank you for your attention and would like to acknowledge my friend and colleague, Dr. Valerie Ward and all the children's hospital sonographers and technologists that have created these images.

Thank you.