October 18, 2023
A tumour capsule is a thin layer of tissue that separates a tumour from the surrounding, normal tissue. Both benign (non-cancerous) and malignant (cancerous) tumours may have a capsule. Tumours surrounded by a capsule are something described as being encapsulated. Tumours that do not have a capsule are described as non-encapsulated.
Pathologists use the term tumour capsule invasion or capsular invasion to describe tumour cells that have broken through the capsule and spread into the surrounding normal tissue (the spread of tumour cells into normal tissue is called invasion). In some parts of the body, capsule invasion is used to distinguish between benign (noncancerous) and malignant (cancerous) tumours made up of very similar-looking cells. For example, follicular adenoma and minimally invasive follicular carcinoma are very similar-looking tumours in the thyroid gland. However, follicular adenoma is a benign tumour while minimally invasive follicular carcinoma is malignant. Both tumours are also surrounded by a capsule. The most important difference is that the cells in minimally invasive follicular carcinoma show capsule invasion while the cells in follicular adenoma do not.
This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report.