Poorly differentiated adenocarcinoma

Poorly differentiated adenocarcinoma is a type of cancer that begins in glandular cells (cells that produce mucus or other fluids), which are found in many organs, including the stomach, intestines, lungs, and pancreas. In this type of cancer, the cancer cells have lost many of their normal structures, making them look very different from the healthy glandular cells they originated from. “Differentiation” describes how similar the cancer cells are to normal cells from the same tissue. When a cancer is “poorly differentiated,” it means the cells have changed so much that they are challenging to recognize. This type of adenocarcinoma tends to grow and spread more quickly than well-differentiated forms.

Where does poorly differentiated adenocarcinoma come from?

Poorly differentiated adenocarcinoma can start in any glandular tissue in the body. Glandular cells are found in many organs, including the digestive system (stomach, intestines, pancreas), respiratory system (lungs), and other organs like the prostate and breast. The tumour cells in poorly differentiated adenocarcinoma lose many features of the original glandular cells, making it difficult to tell where the cancer started just by looking under a microscope.

What is the prognosis for a person with poorly differentiated adenocarcinoma?

The prognosis, or expected outcome, for poorly differentiated adenocarcinoma depends on several factors, including the location of the tumour, its size, whether it has spread to nearby lymph nodes or distant organs, and how it responds to treatment. This type of cancer is generally more aggressive and can be harder to treat, which may lead to a poorer prognosis. However, every case is unique, and treatments like surgery, chemotherapy, and radiation therapy may still be effective in controlling the cancer.

Is poorly differentiated adenocarcinoma an aggressive type of cancer?

Yes, poorly differentiated adenocarcinoma is generally considered an aggressive cancer. Because the cells have lost many of their normal features and are more disorganized, they tend to grow and spread quickly. That makes this type of cancer more challenging to treat, especially if it spreads to other parts of the body.

What stage is poorly differentiated adenocarcinoma?

Poorly differentiated adenocarcinoma is a diagnosis, not a stage. The stage of the cancer is determined by additional information, including the size and location of the primary tumour and whether the tumour cells have spread to nearby lymph nodes or distant organs. Staging helps doctors understand the extent of the cancer and guide treatment planning.

For example:

• Stage I typically indicates a small cancer confined to the original location.
• Stage II and Stage III suggest that the tumour has grown larger or spread to nearby lymph nodes.
• Stage IV means the cancer has spread to distant organs.

The stage provides valuable information about the cancer’s progression and helps guide the treatment approach.

How is this diagnosis made?

Imaging studies, such as CT scans, MRI, or endoscopy, are valuable tools for locating the tumour and assessing its spread. However, a diagnosis of poorly differentiated adenocarcinoma can only be confirmed once a tissue sample has been examined under the microscope by a pathologist. A biopsy is taken to obtain this sample, which the pathologist examines to look for abnormal glandular structures and disorganized cell growth typical of this type of cancer. Immunohistochemistry is often used to detect cytokeratins and other markers that confirm the tumour’s glandular origin and help identify the primary site of the cancer. This careful examination of the tissue sample is essential for making an accurate diagnosis and planning treatment.

What are the microscopic features of poorly differentiated adenocarcinoma?

Under a microscope, poorly differentiated adenocarcinoma comprises very abnormal-looking cells. Pathologists often use the term atypia to describe abnormal cells in size, shape, or colour. The cancer cells frequently have large, irregular nuclei (the central part of the cell that holds DNA) and lack the organized gland-like structures typical of normal glandular cells. These features indicate that the cancer cells have lost many of the characteristics of normal cells and have a higher potential for aggressive behaviour.

What is immunohistochemistry and how does it help in the diagnosis of poorly differentiated adenocarcinoma?

Immunohistochemistry (IHC) is a lab technique that helps pathologists identify the origin of poorly differentiated adenocarcinoma. This technique uses antibodies to detect specific proteins on the surface of cancer cells, which can give clues about where the tumour started.

In poorly differentiated adenocarcinoma, tumour cells should express cytokeratins, proteins made by epithelial cells (cells that line organs and produce mucus or other fluids). Cytokeratins help confirm that the cancer originated from epithelial tissue.

Commonly tested cytokeratins include:

• Pancytokeratins: A broad group of cytokeratins found in many types of epithelial cells.
• Cytokeratins AE1/AE3: A combination of cytokeratins expressed by normal epithelial cells and many adenocarcinomas.
• Cytokeratin 7 (CK7): This cytokeratin is often expressed in cancers originating in the lungs, thyroid gland, upper gastrointestinal tract, female reproductive organs (ovaries, uterus, and cervix), head and neck, and skin.
• Cytokeratin 20 (CK20): This cytokeratin is usually expressed in tumours originating in the lower gastrointestinal tract, such as the colon and rectum.
• Cytokeratin 8/18: A group of cytokeratins found in many types of epithelial cells.

These markers help confirm that the tumour is an adenocarcinoma and can provide information about where it started, guiding diagnosis and treatment decisions.