An example of upper urinary system in situ urothelial carcinoma (CIS).1. Classification of the lesion as a high-grade in situ lesion leads to a nephroureterectomy because no intraluminal therapy is possible – this is a major decision for the pathologist. 2. As in this specimen, the epithelium if often scant, cauterized, detached from the lamina propria, and difficult to interpret (in fact a nightmare) – it is challenging for the urologist to obtain biopsies in the upper collecting system, hence scant sampling is the rule. 3. This case was sent in consultation - the submitting pathologist performed KRT20 – but few cells remain on deeper sectioning. 4. In such cases pathologists usually hesitate to diagnose CIS, reporting equivocal findings but in fact, not all CIS cases show KRT20 expression. 5. In cases like this with convincing cytologic features, a definitive diagnosis of CIS can be rendered despite a negative KRT20, although a positive stain would have been reassuring.
Case courtesy of Professor Alex Kryvenko
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