What is the Pheochromocytoma of the Adrenal Gland Scaled Score (PASS)?
Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) is a tool that doctors use to predict the behaviour of a pheochromocytoma. A score of 3 or less means that the tumour is likely to behave in a non-cancerous manner and is cured by surgery alone. In contrast, a score of 4 or more means the tumour is more likely to behave like cancer and spread to other parts of the body.
In order to determine the PASS score, your pathologist will look for specific microscopic features. Each feature is given a set number of points and which are added up to give the total PASS score.
- Invasion of periadrenal adipose tissue (2 points) – The tumour cells have spread outside the adrenal gland and into the fat that surrounds it.
- > 3 mitoses for every 10 high power fields (2 points) – There are more than 3 dividing cells in a pathologist’s 10 fields of view at 400X magnification (high power fields).
- Atypical mitoses (2 points) – The dividing cells look abnormal when examined under the microscope. This leads to new cells which are unable to function normally.
- Necrosis (2 points) – The tumour cells are dying.
- Cellular spindling(2 points) – The tumour cells are longer than they are round.
- Cellular monotony (2 points) – All of the cells look exactly the same as each other.
- Large nests or diffuse growth (2 points) – The cells are growing in large groups instead of forming small cell balls (zellballen).
- High cellularity (2 points) – There are more tumour cells and they are more closely packed together than normally expected for a pheochromocytoma.
- Marked nuclear pleomorphism (1 point) – All of the cells look very different from each other.
- Capsular invasion (1 point) – The tumour cells have spread past the tumour capsule into the tissue outside of the adrenal gland.
- Vascular invasion (1 point) – The tumour cells are found inside blood vessels.
- Hyperchromatic tumour cells (1 point) – The part of the cell that holds the genetic material, the nucleus, is much darker than normal.
The PASS was developed by Dr. Lester Thompson, a pathologist and expert in the field of head and neck and endocrine pathology.