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A 71-year-old male presents to your office with painless hematuria and left costovertebral angle pain. His body mass index is 33 kg/m^2. A renal biopsy is shown in Figure A. The patient’s mass is most likely a malignancy of which of the following:
Tubular epithelial cells
Perirenal adipose cells
Metastatic adrenocortical carcinoma
Visceral epithelial cells
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The patient presents with classic symptoms of renal cell carcinoma (RCC), including painless hematuria and costovertebral angle pain. Renal cell carcinoma is a malignancy of proximal tubular epithelial cells.
RCC symptoms include painless hematuria, costovertebral angle pain, fever and weight loss. Smoking and obesity are risk factors. The classic triad of Histology shows rounded or polygonal clear cells with abundant clear cytoplasm filled with glycogen and lipid (see image in questions stem). Prognosis is poor, especially if there is involvement of the renal vein.
When approaching this question making the correct diagnosis hinges almost entirely on knowing the histology of RCC. Given the history of painless hematuria a malignancy must be the first thing that comes to mind, particularly without a history of trauma, or a congenital defect. Despite this, the classic triad of RCC (flank pain, hematuria, and a palpable abdominal renal mass) occurs in at most 9 percent of patients. Classically the cells seen in RCC and the description given on Step exams is that of rounded, polygonal cells, abundant in lipids and glycogen. The clear appearance of the cells is a result of lipids and glycogen washing out during preparation for histology. Once the diagnosis of RCC is made, the next step is knowing that this malignancy is of proximal tubular epithelial cells. Keep in mind that a major risk factor for RCC includes smoking - carcinogens are concentrated in the urinary tract and bathe the tubular epithelial cells, leading to malignant transformation.
Figure A shows primary renal cell carcinoma histology with rounded or polygonal clear cells with abundant clear cytoplasm.
2-5. Renal cell carcinoma is a malignancy of proximal tubular epithelial cells; all other cell lines mentioned are not consistent with renal cell carcinoma.
For Step exams it is important to know the epidemiology surrounding RCC. RCC is one of the 10 most common forms of cancer in both men and women (1). 90% of these cancers are believed to be of epithelial cell origin and are referred to as RCC.
Li L, Kaelin WG Jr.
Hematol Oncol Clin North Am. 2011 Aug;25(4):667-86. PMID: 21763962 (Link to Abstract)
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