Renal and urinary tract masses: Pathology review

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Renal and urinary tract masses: Pathology review

Renal system


Renal and urinary tract masses: Pathology review

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USMLE® Step 1 style questions USMLE

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A 52-year-old man comes to the clinic because of vague right-sided back pain over the past two months. He denies any recent trauma, heavy lifting, or new activity. The patient has also noticed a 4.2 kg weight loss during this time, despite not making any changes to diet or activity. The patient has a 20 pack-year smoking history. The patient’s temperature is 37.8°C (100°F), pulse is 75/min, and blood pressure is 128/85 mm Hg. Physical examination shows no abnormalities. The results of his urinalysis are shown below:  
Laboratory value   Result 
 Erythrocytes  60/hpf 
 Leukocytes  4/hpf 
 Bacteria  None 
Which of the following is a possible complication of this patient's condition?  


In the Emergency Department, two people came in. One of them is 68 years old Randy who has left flank pain and gross hematuria. On the physical examination, there’s also a palpable mass in the left abdomen. Randy also has a history of heavy smoking for the past 40 years. The other person is 54 year old Uriah who came in because of painless hematuria. A while ago, Uriah took cyclophosphamide for a condition he had called Hodgkin’s disease. Both individuals had an ultrasound done, which showed a mass in Randy’s left kidney and a mass in Uriah’s bladder.

Okay, Randy has a mass in his left kidney, while Uriah has a mass in his bladder. Let’s first talk about renal masses, which can develop in both adults and children. These masses may be either cysts or tumor. In turn, renal cysts can be either simple or complex, while tumors can be benign, like renal oncocytoma, or malignant, like renal cell carcinoma. Regarding masses of the urinary tract, the main concerns are transitional cell carcinoma and squamous carcinoma of the bladder.

Let’s look at them one by one. Simple cysts are very common and account for most of renal masses. They are typically small and occur in adults with otherwise healthy kidneys. On an abdominal ultrasound, they’re perfectly round and have a thin wall and are filled with fluid. This liquid is basically the produced by the kidney. The ultrafiltrate is the plasma without proteins that results after the filtration process, that happens in the glomeruli, specifically in Bowman’s capsule. This makes simple cysts anechoic on ultrasound, since the fluid does not produce an echo and thus appear black. Usually they’re asymptomatic and are discovered incidentally during an ultrasound or a CT-scan done for other reasons. On the other hand, complex cysts are larger than simple cysts. Additionally, on an ultrasound, they have thick, irregular walls and are multilocular- meaning they have septations within, that separate the cyst cavity into compartiments. Sometimes, complex cysts may even have a solid component within. Now, complex cysts are more likely to cause symptoms, like flank pain, for example. They also have a higher chance of becoming malignant and that’s why, for your tests, remember that complex cysts require additional follow up and even surgical removal.


Renal and urinary tract masses are abnormal growths that can develop in the kidneys, ureters, bladder, and urethra. These masses may be either cysts or tumors. Renal cysts on ultrasounds appear to be tiny sacs filled with black fluid. Cysts can be either simple or complex when they have septations within. Renal tumors can be benign, like renal oncocytoma, or malignant, like renal cell carcinoma. Common urinary tract tumors include: Renal cell carcinoma: the most common type of renal cancer. It develops in the renal tubules and can metastasize to surrounding tissue. Transitional cell carcinoma: develops in the urothelial cells lining the urinary tract. Wilms' tumor: a rare type of kidney cancer typically affecting children.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Robbins and Cotran Pathologic Basis of Disease" Saunders (2015)
  4. "Fundamentals of Pathology" H.A. Sattar (2011)
  5. "Renal cell carcinoma" The Lancet (2009)
  6. "Gemcitabine and Cisplatin Versus Methotrexate, Vinblastine, Doxorubicin, and Cisplatin in Advanced or Metastatic Bladder Cancer: Results of a Large, Randomized, Multinational, Multicenter, Phase III Study" Journal of Clinical Oncology (2000)
  7. "Maintaining protein stability of ∆Np63 via USP 28 is required by squamous cancer cells" EMBO Molecular Medicine (2020)

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