Clear cell adenocarcinoma of the urethra

Clear cell adenocarcinoma of the urethra, also primary urethral clear cell adenocarcinoma, is a very rare malignant tumour of the urethra.

General

• Predominantly in women.

Pathogenesis not well understood - may arise from:

• Muellerian rests or urothelium.
• Shed kidney cells.
• Nephrogenic adenoma - malignant transformation.

Microscopic

Features:

• Clear cells (at least focally).
  • Columnar or cuboidal morphology.
  • At least moderate nuclear pleomorphism.
• Hobnailing (classic feature).

Note:

• Described as morphologically similar to clear cell adenocarcinoma of the gynecologic tract - see clear cell carcinoma of the uterine cervix.

DDx:

• Nephrogenic adenoma - also has hobnailing, not mitotically active, no necrosis, no or mild nuclear atypia.
• Clear cell renal cell carcinoma.
• Clear cell adenocarcinoma of the gynecologic tract.
• Other clear cell tumours.

Images

www:

• CCA of the urethra (nih.gov).
• CCA of the urethra (nih.gov).

IHC

Features:

• PAX8 +ve/-ve (2 +ve in 4 cases).
• CK7 +ve/-ve (2 +ve in 4 cases).
• Vimentin +ve (3 +ve in 4 cases).
• CK20 -ve/+ve (1 +ve in 4 cases).

Others:

• ER -ve.
• p63 -ve.
• PSA -ve.
• p16 -ve.
• Ki-67 ~ 47/200 on average cells.
  • 5.5/200 cells on average in nephrogenic adenoma.

See also

• Clear cell adenocarcinoma.
• Clear cell tumours.