Anaplastic is an adjective used to describe tumor cells that have lost the normal appearance and organization of the tissue they came from. When a pathologist describes cells or a tumor as anaplastic, it means those cells look highly abnormal under the microscope — they have shed the specialized features of normal tissue and no longer resemble the cells from which they originated. Anaplastic is the adjective form of the noun anaplasia, which describes this process in full detail.
How is the word “anaplastic” used in a pathology report?
You may see the word “anaplastic” used in two ways in a pathology report:
- As a descriptor of tumor cells — for example, “anaplastic cells are present” or “the tumor shows anaplastic features.” This means the pathologist has identified cells that look markedly abnormal, with enlarged, irregular nuclei, variable sizes, and a disorganized arrangement. This is a sign of high-grade, aggressive tumor behavior.
- As part of a cancer’s name — some cancer types include the word “anaplastic” in their official name to indicate that they are a particularly aggressive, high-grade form of that cancer. Examples include anaplastic thyroid carcinoma and anaplastic large cell lymphoma.
Which cancers are named “anaplastic”?
Several specific cancers use the term anaplastic in their name to signal aggressive, high-grade behavior:
- Anaplastic thyroid carcinoma — the most aggressive form of thyroid cancer, characterized by rapid growth and a poor prognosis.
- Anaplastic large cell lymphoma (ALCL) — a type of non-Hodgkin lymphoma in which the tumor cells are markedly abnormal. ALCL is divided into ALK-positive and ALK-negative subtypes.
- Anaplastic astrocytoma — a high-grade brain tumor that is more aggressive than lower-grade astrocytomas.
- Glioblastoma — the most aggressive primary brain tumor, characterized by marked anaplasia throughout.
What does it mean for my diagnosis?
When a pathologist uses the word “anaplastic” in your report, it indicates that the tumor cells look highly abnormal — a feature associated with malignant behavior, faster growth, and a higher likelihood of spread. Anaplastic features are almost never seen in benign tumors. The finding will influence how your oncologist approaches your treatment. For a full explanation of what anaplastic cells look like, how they relate to tumor grade, and what this means for your care, see the main article on anaplasia.
Questions to ask your doctor
- My report describes anaplastic cells — what grade is my tumor, and how does this affect my treatment?
- Is the word “anaplastic” part of my cancer’s name, or is it describing a feature of the cells?
- What does the presence of anaplastic cells mean for my prognosis?
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