What is SDHB?

Reviewed by Pathologists on:
January 9, 2026

SDHB stands for succinate dehydrogenase subunit B, which is a protein made by cells to help produce energy. It is part of a larger group of proteins called the succinate dehydrogenase (SDH) complex, which works inside cells to convert nutrients into usable energy.

SDHB itself is not a disease. Instead, it is a normal protein that pathologists test for because changes in SDHB can be linked to specific tumours.

What does the SDH complex do?

The SDH complex plays a role in how cells generate energy from oxygen and nutrients. It works inside small structures called mitochondria, which are often described as the “power plants” of the cell.

When the SDH complex is working normally, cells can efficiently produce energy and regulate normal growth. When the SDH complex is not working properly, cells may accumulate abnormal substances that can promote tumour development.

Why is SDHB important in pathology?

SDHB is essential because the loss of SDHB protein can be a clue that the SDH complex is not functioning normally. Pathologists use SDHB testing as a screening tool to identify tumours that may be related to SDH dysfunction.

Loss of SDHB does not by itself diagnose a specific tumour, but it helps narrow down the possibilities and may point to an underlying genetic cause.

How is SDHB tested?

SDHB is most commonly tested using immunohistochemistry, a laboratory technique that uses special stains to detect proteins in tissue samples.

• Normal (retained) SDHB expression means the SDH complex is likely functioning normally.

• Loss of SDHB expression means the protein is absent from tumour cells, suggesting dysfunction of the SDH complex.

Importantly, when SDHB is lost in tumour cells, normal surrounding cells usually still show SDHB staining. This internal comparison helps pathologists interpret the result accurately.

What types of tumours are associated with SDHB loss?

Loss of SDHB expression is most commonly seen in:

• Paragangliomas and pheochromocytomas, which are tumours arising from neuroendocrine cells.

• Certain gastrointestinal stromal tumours (GISTs), particularly those not driven by more common genetic changes.

• Rare kidney tumours and other uncommon neoplasms linked to SDH dysfunction.

Not all tumours in these groups show SDHB loss, but when it is present, it provides essential diagnostic information.

Does SDHB loss mean the tumour is inherited?

Not always, but it can be a clue. Loss of SDHB expression may be associated with inherited genetic conditions involving SDH genes. These conditions can increase the risk of developing certain tumours.

Because of this possibility, doctors may recommend genetic counseling or genetic testing, mainly if SDHB loss is found in a tumour or if there is a family history of related cancers.

Why might SDHB be mentioned in my pathology report?

SDHB may be mentioned to explain why a tumour was tested for SDH dysfunction and what the results showed. The report may state whether SDHB expression is retained or lost, which helps guide diagnosis and further testing.

Your doctor will interpret this finding together with the tumour type, location, and other test results.

Questions to ask your doctor

• Was SDHB expression retained or lost in my tumour?

• What does this result suggest about my diagnosis?

• Do I need genetic counseling or genetic testing?

• Does this finding affect my treatment or follow-up plan?

• Are my family members at increased risk?