clear cell carcinoma
Meaning of clear cell carcinoma: A description of what the cells look like on a slide, applied to tumors that arise in several unrelated organs.
Definition of clear cell carcinoma
Clear cell carcinoma is a name given to cancers whose cells appear almost empty and glassy under the microscope. The clear look is an artifact of preparation: the cells are loaded with fat and glycogen, and both dissolve away during processing, leaving a pale space behind a thin rim. Tumors with this appearance occur in the kidney, the ovary, the lining of the womb and the cervix.
Why do the cells look clear?
A slide is made by soaking tissue in solvents to remove water, embedding it in wax and cutting thin sections. Fat and glycogen dissolve in those solvents and are washed out. Cells that were packed with both are left as little more than an outline with the nucleus pressed to one side. Nothing about the living cell is empty; the emptiness is created in the laboratory. Special stains applied before processing can confirm what was there.
Where does it occur?
| Organ | Notes |
|---|---|
| Kidney | By far the commonest site, and the usual meaning of the term |
| Ovary | Linked with endometriosis |
| Lining of the womb | Uncommon and typically aggressive |
| Cervix and vagina | Rare |
| Salivary gland | Rare |
Is it one disease?
No, and this is the point most easily missed. The shared appearance does not imply shared biology. Clear cell renal cell carcinoma arises from the lining of the kidney tubule and is driven in most cases by loss of the VHL gene, which pushes the cell to behave as though starved of oxygen and to build blood vessels. Clear cell carcinoma of the ovary arises from a completely different tissue with different genetic changes and different treatment. A carcinoma is classified first by where it started and only then by how it looks.
How does it relate to adenocarcinoma?
Most examples outside the kidney are a subtype of adenocarcinoma, meaning a cancer arising from gland-forming tissue. The older name mesonephroma, once used for the ovarian form, reflected a mistaken belief about its origin and has been abandoned.
Also known as
Used in a sentence
The nephrectomy specimen showed a clear cell carcinoma confined to the kidney.
Good to know
The clear appearance is a laboratory artifact and describes several unrelated tumors, so the organ of origin, not the appearance, determines classification and treatment.
Word origin
Where “clear cell carcinoma” comes from
Carcinoma comes from the Greek karkinos, meaning crab, a name applied to invasive tumors in antiquity.