D2-40 is the name of a stain that pathologists use to find a protein called podoplanin in a tissue sample. Podoplanin is found in the cells that line lymphatic vessels, the thin channels that drain fluid from tissues and carry immune cells around the body. Because the D2-40 stain highlights these vessels clearly, it is one of the most useful tools pathologists have for telling lymphatic vessels apart from blood vessels. Podoplanin is also present in several other normal cell types and in certain tumors, which makes D2-40 helpful for identifying what kind of tumor is present. D2-40 is a diagnostic stain: it helps the pathologist reach a diagnosis and describe what they see. It is not a test that determines which treatment a patient receives. This article explains what D2-40 is, why it is used, and what the results mean.
Why do pathologists test for D2-40?
Pathologists use D2-40 for two main reasons.
The first, and most common, is to identify lymphatic vessels in a tissue sample so they can determine whether cancer cells are inside them. This finding is called lymphatic invasion, and it is part of what pathologists describe as lymphovascular invasion. Under ordinary stains, small lymphatic vessels can be difficult to distinguish from blood vessels or from spaces created while the tissue was being processed. The D2-40 stain specifically marks the lining of lymphatic vessels, which helps the pathologist confirm whether cancer cells are truly inside a lymphatic vessel. When cancer cells are found inside lymphatic vessels, it suggests the cancer has gained access to a route that can carry it to nearby lymph nodes. This information is used to estimate the risk that the cancer has spread and to help guide treatment decisions.
The second reason is to help identify the type of tumor. Because podoplanin is present in some tumors and absent in others, the D2-40 result can help separate tumors that look similar under the microscope. This is especially useful in diagnosing mesothelioma and certain tumors of blood and lymphatic vessels.
How do pathologists test for D2-40?
D2-40 is performed using immunohistochemistry, a test in which a special antibody is applied to a thin slice of tissue. If the target protein is present, the antibody attaches to it and produces a color change that the pathologist can see under the microscope. The result is reported as positive or negative:
- D2-40 positive — The protein was detected in the cells being examined. When lymphatic vessels stain positive, the pathologist can see their outlines clearly and check whether cancer cells are inside them. When tumor cells themselves stain positive, this supports certain diagnoses.
- D2-40 negative — The protein was not detected in the cells being examined. On its own, a negative result does not rule out a diagnosis. It is interpreted alongside the appearance of the tissue and the results of other stains.
A D2-40 result is never interpreted on its own. Pathologists combine it with the microscopic appearance of the tissue, the clinical history, and often several other stains before reaching a final diagnosis.
Which normal cells are positive for D2-40?
The protein detected by D2-40 is normally present in several types of healthy cells. Knowing where it is normally found helps pathologists interpret the stain correctly. Normal cells that are typically positive include:
- Lymphatic endothelial cells — The cells that line the inside of lymphatic vessels. This is the most important use of the stain.
- Mesothelial cells — The cells that line the outer surface of organs and the inside of the chest and abdominal cavities.
- Myoepithelial cells — Specialized cells in the breast and salivary glands that help move fluid through ducts.
- Adrenal cortical cells — Cells from the outer layer of the adrenal glands.
- Follicular dendritic cells — Immune cells found in lymph nodes that help trap and display foreign particles.
- Granulosa cells — Cells in the ovaries that support the development of eggs.
- Basal cells — The deepest cells of the skin and of squamous surfaces such as the lining of the mouth.
Which tumors can be positive for D2-40?
D2-40 can be positive in both noncancerous (benign) and cancerous (malignant) tumors, which is why the result is always interpreted in context.
Noncancerous tumors that can be positive include dermatofibroma (a common skin growth), myoepithelioma and other tumors made of myoepithelial cells, odontogenic tumors such as ameloblastoma (tumors that develop in the jaw from tooth-forming tissue), and hemangiomas and lymphatic malformations (growths made of blood or lymphatic vessels).
Cancerous tumors that can be positive include:
- Mesothelioma — A cancer that arises from the lining of the lungs, abdomen, or heart. D2-40 is one of the standard stains used to support this diagnosis.
- Angiosarcoma and Kaposi sarcoma — Cancers that arise from the cells lining blood and lymphatic vessels.
- Germ cell tumors — Including seminoma and some embryonal carcinomas.
- Squamous cell carcinoma — A common cancer of the skin and of mucosal surfaces such as the mouth and throat.
- Serous carcinoma — A cancer that can arise in the ovary, such as high-grade serous carcinoma, or in the uterus, such as endometrial serous adenocarcinoma.
- Adrenocortical carcinoma — A rare cancer of the adrenal gland.
- Follicular dendritic cell sarcoma — A rare tumor arising from immune cells found in lymph nodes.
- Pleomorphic carcinoma of the lung — An uncommon type of lung cancer.
Questions to ask your doctor
- Why was the D2-40 stain used on my sample?
- Was D2-40 used to look for lymphatic invasion, to identify my tumor type, or both?
- Did my report describe lymphatic or lymphovascular invasion?
- If lymphatic invasion was found, what does that mean for my treatment and follow-up?
- What diagnosis do the D2-40 and other stain results support?
- Were any other stains performed, and what did they show?
- Is any further testing needed to confirm the diagnosis?
Related articles on MyPathologyReport.com
We are proud to partner with:
