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Carcinoma in situ of the bladder

Tuesday 21 October 2014

urothelial carcinoma in situ

PO

- Flat lesion composed of cells in mid to upper epithelium with high cytologic grade
- By definition, no invasion into lamina propria

Note: "high grade non-invasive papillary lesions" are NOT designated "carcinoma in situ" to avoid confusion

Microscopy

- Flat lesion composed of cells with large, irregular, hyperchromatic nuclei, prominent nuclear pleomorphism, high N/C ratio, mitotic figures in mid to upper epithelium
- Atypia may not be full thickness
- Epithelium is often denuded
- Nuclear size is 5x that of lymphocytes vs 2x lymphocytes for normal urothelium (Hum Pathol 2001;32:997)
- Also (but less important) loss of polarity, nuclear crowding, irregular thickness of urothelium
- Cells are not cohesive, leading to shedding into urine
- Occasionally present in prostatic ducts, spreads by intramucosal extension

Variants

- Large cells with pleomorphism,
- large cells without pleomorphism,
- small cell,
- clinging (single layer of atypical cells on denuded urothelium),
- cancerization of urothelium (pagetoid - Hum Pathol 1993;24:1199, undermining or overriding)
- Microinvasion (2 mm or less) demonstrates invasive cells with retraction artifact mimicking vascular invasion (77% of cases of microinvasion)
- Also nests or irregular cords, rarely invades as isolated single cells with or without desmoplasia (Am J Surg Pathol 2001;25:356)

Note: "high grade non-invasive papillary lesions" are NOT designated as "carcinoma in situ" to avoid confusion