Urothelial Tumors

Grading system

•    WHO/ISUP Grading

o    Urothelial papilloma

o    Papillary urothelial neoplasm of low malignant potential (PUNLMP)

o    Papillary urothelial carcinoma of low grade

o    Papillary urothelial carcinoma of high grade

o    ?Carcinoma in situ

Histology of each grade

Urothelial papilloma

o    Arise singly as small (0.5-2.0 cm) delicate structures superficially attached to the mucosa by a stalk.

o    The individual finger-like papillae consist of a central core of loose fibrovascular tissue covered by transitional epithelial cells that are histologically identical to normal transitional epithelium

Papillary urothelial neoplasm of low malignant potential (PUNLMP)

o    Similar to histologic appearance of urothelial papilloma, however the urothelium lining the fibrovascular core may be thicker or possess diffuse nuclear enlargement.

o    Mitotic figures are rare.

o    PUNLMPs tend to be larger than papillomas and may be indistinguishable from low or high-grade papillary urothelial carcinoma.

Papillary urothelial carcinoma of low grade

o    Characterized by an orderly appearance both architecturally and cytologically

o    Cells are evenly spaced, maintain polarity and are cohesive.

o    There is minimal, but definite evidence of nuclear atypia (hyperchromatic nuclei, infrequent mitotic figures predominantly located towards the base, and mild nuclear pleiomorphism).

Papillary urothelial carcinoma of high grade

o    Cells are dyscohesive and possess definite nuclear atypia.

o    Tumour cells have large, hyperchromatic nuclei, and may possess frank anaplasia.

o    Frequent mitoses which are sometimes aberrant

o    Architecturally, the epithelium demonstrates disarray; the cells lack polarity

Carcinoma in situ

o    Dyscohesive cells with severe nuclear atypia (large, hyperchromatic nuclei, high nuclear pleiomorphism, may be anaplastic, numerous mitotic figures which may be aberrant).

o    Architecturally flat; may be full thickness atypia, or scattered atypical cells in otherwise normal urothelium.

Risk factors in bladder cancer

•    Industrial exposure to arylamines

•    Cigarette smoking

•    Schistosoma haematobium infections

•    Long-term use of analgesics

•    Heavy exposure to cyclophosphamide

•    Prior exposure to bladder radiation

Other types of bladder cancer

•    Squamous cell carcinoma : associated with Schistosoma haematobium infections or chronic bladder irritation and infection.

•    Adenocarcinoma: arise from urachal remnants or extensive intestinal metaplasia.