Tumor Necrosis: Definition

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Tumor necrosis means areas of dead cells inside a tumor. Pathologists see these areas under the microscope. Necrosis can mean different things depending on when it appears. Before treatment, it can be a sign of fast growth. After treatment, it often shows that the treatment worked.

This article explains what causes tumor necrosis, why it matters, how pathologists measure it, and what your report may say.

What is tumor necrosis?

Tumor necrosis is the death of groups of cells within a tumor. Necrosis is the general term for cell death caused by injury. In a tumor, the dead cells lose their normal structure and break down. Under the microscope, the pathologist sees patches of dead tissue next to living tumor cells.

What causes tumor necrosis?

Tumor cells die for two main reasons:

Not enough blood supply. A tumor can grow faster than the blood vessels that feed it. Cells far from a vessel run out of oxygen and nutrients, and they die.
Treatment. Chemotherapy and radiation kill tumor cells directly. They can also damage the vessels that feed the tumor.

Why is tumor necrosis important?

The meaning of necrosis depends on whether the tumor received treatment first:

Before treatment. Necrosis can be a sign that a tumor is growing quickly. In some cancers, it helps set the grade or the diagnosis. A higher grade often means a tumor is more likely to grow and spread.
After treatment. Necrosis usually shows that the treatment killed tumor cells. A large amount of necrosis is a good sign in this setting.

How does necrosis affect the diagnosis or grade?

In some tumors, the presence or amount of necrosis is part of the formal rules. Examples include:

Soft tissue sarcoma. The FNCLCC grading system scores necrosis from 0 to 2. No necrosis scores 0, necrosis in less than half the tumor scores 1, and half or more scores 2. The score helps set the grade.
Carcinoid tumor of the lung. Necrosis separates an atypical carcinoid from a typical carcinoid. Any necrosis makes the tumor atypical.
Glioblastoma. Necrosis supports the diagnosis of glioblastoma. The living tumor cells often line up around the dead area in a fence-like pattern called palisading.
Breast DCIS. Pathologists use the term comedonecrosis for dead cells in the center of a cancer-cell-filled duct. It is most common in ductal carcinoma in situ.

What does necrosis after treatment mean?

After chemotherapy or radiation, the pathologist examines the tumor bed to see how much of the tumor died. More necrosis usually means a better response. For some tumors, the pathologist reports the percentage of tumor killed.

Osteosarcoma is a clear example. When 90% or more of the tumor is dead at surgery, doctors call it a good response. This links to a better outcome. A lower percentage guides the next steps, and many people with a poorer response are still cured.

How do pathologists measure tumor necrosis?

The pathologist examines tumor slides under the microscope. The pathologist estimates how much of the tumor is dead, often as a percentage. For a large tumor, the pathologist may examine many slides to make a reliable estimate. The pathologist also notes the pattern of necrosis when it matters for the diagnosis.

What might my report say about tumor necrosis?

Reports describe tumor necrosis in a few standard ways. Each laboratory phrases them a little differently:

Necrosis present or absent. The report states whether the pathologist saw necrosis.
Percentage of necrosis. The report gives the share of the tumor that is dead, such as “necrosis: 30%.”
Necrosis score. In sarcomas, the report may list a necrosis score of 0, 1, or 2 as part of the grade.
Treatment effect. After treatment, the report may describe necrosis as treatment effect or as a percentage of response.
A named pattern. The report may name a pattern, such as comedonecrosis or palisading necrosis.

Questions to ask your doctor

Did my tumor show necrosis?
How much of my tumor was necrotic?
Does the necrosis change the grade or diagnosis of my tumor?
Did I receive treatment before surgery, and does the necrosis show a response?
What does this finding mean for my outlook?
Does this finding change my treatment plan?