Duct

In pathology, a duct refers to a tube-like structure in the body that transports fluids from one area to another. Ducts are important parts of various organ systems, allowing for the movement of substances such as bile, urine, sweat, and breast milk.

Types of cells in a duct

Ducts are lined with epithelial cells, which form a protective barrier and can vary in shape and size depending on the duct’s location and function. Some ducts may also have muscle cells in their walls to help propel fluids through them.

The function of a duct

The primary function of a duct is to help move fluids from glands or organs, where the fluids are produced, to other parts of the body or the external environment. These fluids can include digestive enzymes, hormones, waste products, and other substances essential for body functions. Ducts ensure that these fluids reach their intended destinations efficiently and safely.

Where are ducts normally found in the body?

Ducts are found throughout the body in various systems:

• Digestive system: Ducts in the liver and pancreas transport bile and digestive enzymes into the intestines to help with digestion.
• Excretory system: The urinary tract includes ducts such as the ureters, which carry urine from the kidneys to the bladder.
• Reproductive system: In males, ducts transport sperm from the testes to the outside of the body. In females, the fallopian tubes serve as ducts for eggs to travel from the ovaries to the uterus.
• Endocrine system: Although not ducts in the traditional sense, some endocrine glands release hormones directly into the bloodstream or use duct-like structures for hormone secretion.
• Sweat glands: Ducts carry sweat from the glands to the surface of the skin.

Cancers that start from ducts

Cancers that arise from ducts are generally referred to as carcinomas, which are cancers that begin in the epithelial cells lining the inside of the ducts. Since ducts are found in various parts of the body, the type of cancer can vary based on the location and function of the duct involved.

Here are some specific examples:

• Breast cancer: One of the most common types of ductal cancer is breast cancer, specifically ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC). DCIS is a non-invasive cancer where abnormal cells are found in the lining of a breast duct but haven’t spread outside the duct. IDC, on the other hand, begins in a milk duct and invades the surrounding breast tissue, and it can potentially spread to other parts of the body.
• Pancreatic cancer: Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer, starting in the ducts of the pancreas. This cancer is particularly aggressive and often diagnosed at a late stage.
• Bile duct cancer: This type of cancer, also known as cholangiocarcinoma, occurs in the bile ducts, which carry bile from the liver and gallbladder to the small intestine. It’s a rare but aggressive form of cancer.
• Salivary gland cancer: Some cancers of the salivary glands can begin in the ducts that transport saliva from the gland into the mouth. These can include salivary duct carcinoma and others.

Each of these cancers starts in the cells lining the ducts of their respective organs, showcasing the diverse roles and locations of ducts within the body. The treatment and prognosis for ductal cancers can vary widely depending on the cancer type, stage at diagnosis, and other factors.

What does it mean if a duct is dilated?

In pathology, a duct is described as dilated if it is larger than normal. Ducts often become dilated if something (such as a tumour) is blocking one end of the duct which causes the duct behind the blockage to fill up with fluid and stretch.

What does it mean if a duct is obstructed?

In pathology, obstruction of a duct means that something is blocking the inside of the duct. For example, the duct leading from the parotid gland to the mouth can become obstructed by a stone or sialolith which can cause pain or swelling in the parotid gland.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us with any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

Other helpful resources

Atlas of Pathology