In pathology, endophytic describes a growth that extends downward from the surface of a tissue into the organ or tissue below, rather than outward. Pathologists sometimes use the word inverted to mean the same thing. The opposite of endophytic is exophytic, which describes a growth that projects outward from the surface.
Endophytic describes the shape and direction of a growth, not what the growth is. It is not a diagnosis on its own, and it does not indicate whether a growth is harmless or cancerous. Both benign (noncancerous) and malignant (cancerous) growths can be endophytic. The word should always be read together with the rest of the pathology report, especially the type of cells involved. This article explains what endophytic means, how the pattern is recognized, and why it can matter.
Endophytic versus exophytic
Endophytic and exophytic describe opposite directions of growth from a surface such as the skin, the lining of the nose, the cervix, or the inside of the bladder:
- Endophytic — The growth extends inward and downward, into the tissue beneath the surface. Because it grows into the tissue, it may create only a small bump, a thickened area, or almost no visible change on the surface.
- Exophytic — The growth projects outward from the surface, forming a visible lump, wart-like bump, or finger-like projections.
Some growths show both patterns at once, growing outward from the surface while also extending downward into the tissue below. In that situation, a report may describe the growth as having both endophytic and exophytic components.
How is an endophytic growth pattern identified?
An endophytic pattern can be recognized in more than one way. A pathologist may see it while examining the tissue by eye during the gross examination, and it is often clearest under the microscope, where the full depth of the growth and its relationship to the surface can be seen. Doctors may also suspect an endophytic pattern before surgery, during an examination or a procedure such as endoscopy, when an area feels firm or thickened but shows little on the surface.
Under the microscope, an endophytic growth appears as a downward extension of surface cells into the tissue below, often forming rounded nests, cords, or inward-folding sheets. An important part of the assessment is whether the growth is simply pushing the deeper tissue aside as it expands, or is truly invading it. A growth can extend deeply in an orderly, pushing way and still be benign.
What kinds of growths can be endophytic?
Endophytic growth is described in many parts of the body, in both benign and cancerous conditions. Examples include:
- Sinonasal papilloma — A benign growth in the nose and sinuses. One type, the inverted (endophytic) form, grows down into the underlying tissue and is a classic example of this pattern.
- Basal cell carcinoma of the skin — A common skin cancer that frequently grows downward into the deeper layers of the skin.
- Cervical cancer — Some cervical cancers grow mainly inward into the wall of the cervix rather than outward into the vagina.
- Squamous papilloma — A benign surface growth that is usually exophytic but can occasionally show an inverted pattern.
Why does an endophytic growth pattern matter?
On its own, an endophytic pattern is neither good nor bad. It can matter in a few practical ways, depending on where the growth is and what it is:
- It can be harder to see — Because much of the growth lies beneath the surface, it may appear smaller on examination than it actually is, and its true extent may only become clear once the tissue is examined.
- It affects how the growth is measured — For many tumors, how deeply the growth extends is an important measurement recorded in the report, and it can influence staging and treatment.
- It can affect surgical planning — A growth extending downward may require removal of deeper tissue to ensure the margins are clear of the growth.
- It can be part of the diagnosis — For a few specific conditions, such as the inverted type of sinonasal papilloma, the endophytic pattern is one of the features that defines the diagnosis.
Questions to ask your doctor
- What type of growth was described as endophytic in my report?
- Is the growth benign or cancerous?
- How deeply did the growth extend into the tissue?
- Does the endophytic pattern change my treatment or the type of surgery I need?
- Were the margins clear of the growth?
- Does this pattern make it more likely that the growth could come back?
- Will I need any follow-up examinations?
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