Pathology reports use words such as benign and malignant to describe what was found, and words such as atypical and suspicious to show how sure the pathologist is. A benign result means noncancerous, and a malignant result means cancer. Atypical and suspicious results fall in between, and they are among the most confusing words a patient can read. This article explains what these words mean, why a pathologist sometimes cannot give a definite answer, and what usually happens after an uncertain result.
What two questions does a pathology diagnosis answer?
A pathology diagnosis answers two separate questions, and benign, malignant, atypical, and suspicious do not all answer the same one. The first question is what kind of change is present, ranging from normal tissue to cancer. The second question is how certain the pathologist is about that answer. Keeping these two questions apart makes most reports much easier to read.
For example, “malignant” answers the first question, because it says the change is cancer. “Suspicious for malignancy” answers both questions at once, because it says cancer is likely but not proven. “Atypical” usually answers the second question, because it says the cells are abnormal but the pathologist cannot yet say what kind of change they represent. The sections below explain the words used for each question.
What words describe how a growth behaves?
Pathologists use a small set of words to describe how a growth behaves, from harmless to cancer. These words describe the type of change, not how certain the pathologist is. The most common ones are listed below, from least to most serious.
- Normal or no abnormality. The tissue looks as expected for that part of the body. A report may also describe reactive changes, which are cells that look different because of irritation, inflammation, or healing, not because of a tumor.
- Benign. A benign growth, also called a benign neoplasm, is noncancerous. It may grow, but it does not invade surrounding tissue or spread to other parts of the body.
- Precancerous. A precancerous change contains abnormal cells that have not yet become cancer, but could over time. Common examples are dysplasia, intraepithelial neoplasia, and some types of hyperplasia with atypia.
- Borderline or uncertain malignant potential. A small number of tumors behave somewhere between benign and malignant. They are called a borderline tumor or a tumor of uncertain malignant potential. Most behave well, but a few can come back or spread.
- Malignant, noninvasive. Carcinoma in situ means cancer cells are present but have stayed inside the layer where they started. Because they have not invaded deeper tissue, they cannot spread, and some systems treat in situ disease as the highest grade of precancer.
- Malignant, invasive. An invasive cancer has grown beyond its starting layer into the surrounding tissue. Invasive cancer can spread to lymph nodes and other organs, which is called metastasis.
The name of a diagnosis often hints at where it falls on this list. Names ending in “-oma,” such as lipoma, are often benign. Names that include carcinoma or sarcoma are malignant. Lymphoma and melanoma are also cancers, even though they end in “-oma.”
What words describe how certain the pathologist is?
Pathologists use a second set of words to show how certain they are about a diagnosis. These words are especially common in reports from small biopsies and cytology samples, where only limited material is available. The most common ones are listed below.
- Negative or benign. No cancer or precancer was found in the sample. A report may say “negative for malignancy.” This describes only the tissue that was examined.
- Atypical. Some cells look abnormal, but not abnormal enough to call precancer or cancer. The change may be harmless, precancerous, or occasionally cancer, and more information is usually needed.
- Suspicious. The cells have many features of cancer, but not quite enough to be certain. A result that is suspicious for malignancy means cancer is likely, and it is usually treated as a strong reason for further testing or treatment planning.
- Positive or malignant. The pathologist is confident that cancer is present. A report may say “positive for malignancy” or name the type of cancer.
- Nondiagnostic or insufficient. The sample did not contain enough of the right cells or tissue to answer the question. A nondiagnostic result, also called insufficient for diagnosis, is neither reassuring nor worrying. It means the test needs to be repeated or another type of sample is needed.
What do phrases like “consistent with” and “cannot be excluded” mean?
Pathology reports often use short phrases that show how certain the pathologist is about a diagnosis. Pathologists choose these phrases carefully, and each carries a slightly different meaning. Patients often read them as vague, but they precisely describe the limits of a sample.
- Consistent with or compatible with. The findings match the named diagnosis. These phrases are often used when the diagnosis also depends on information outside the sample, such as symptoms or imaging.
- Favor, suggestive of, or most likely. The pathologist leans toward one diagnosis, but cannot fully confirm it from this sample.
- Cannot be excluded or cannot be ruled out. The named diagnosis is possible but less likely. This phrase is often used for cancer when a small sample shows a worrying feature that is not conclusive.
- No evidence of. The pathologist looked for a specific finding and did not see it in the sample. This is a negative result for that finding.
- See comment. The diagnosis line is short, and the comment section explains the reasoning, sample limitations, or recommended next steps. The comment is often the most useful part of an uncertain report.
- Differential diagnosis. A list of possible diagnoses the pathologist is considering. The list usually narrows once more tissue or more tests are available.
What does “atypical” mean in a pathology report?
The word atypical is used in three different ways in pathology reports, which is why it causes so much confusion. Its meaning depends on whether it describes the cells, forms part of a diagnosis name, or names a category in a cytology report. Reading the whole phrase, not just the word atypical, is the key to understanding it.
- A description of the cells. Atypia means the cells look different from normal cells, often with larger or darker nuclei. It can be caused by inflammation, healing, or radiation, as well as by a tumor. The pathologist uses the rest of the report to explain the most likely cause.
- Part of a specific diagnosis. Some diagnoses include the word atypical in their name, and each one means something different. Atypical ductal hyperplasia of the breast is a high-risk change, atypical endometrial hyperplasia is a precancer, and an atypical meningioma is a brain tumor of intermediate grade. These are definite diagnoses, not uncertain results.
- An uncertain category. In cytology and some biopsy reports, atypical is a category between negative and suspicious. Examples include ASC-US on a Pap test and atypical small acinar proliferation (ASAP) on a prostate biopsy. These results usually lead to more testing.
How do cytology reports use these categories?
Cytology reports, which describe individual cells rather than tissue samples, often use a standardized ladder of categories from benign to malignant. A cytology report may come from a Pap test, a fine needle aspiration, or a fluid sample such as urine. Because cells give less information than tissue, cytology systems use uncertain categories more often than tissue biopsies do.
Most cytology systems share the same basic ladder, from negative at one end to malignant at the other, with atypical and suspicious in between. Each step up the ladder carries a higher chance that cancer is present. Most systems also have a nondiagnostic category for samples that cannot be assessed. Two widely used examples are described below.
- Thyroid fine needle aspiration. The 2023 Bethesda System for Reporting Thyroid Cytopathology, now in its third edition, has six categories numbered I to VI. The middle categories are atypia of undetermined significance (AUS), follicular neoplasm, and suspicious for malignancy. Fewer than 1 in 20 nodules called benign turn out to be cancer, while almost all nodules called malignant do.
- Urine cytology. The Paris System for Reporting Urinary Cytology, revised in 2022, focuses on finding high-grade bladder cancer. Its categories run from negative for high-grade urothelial carcinoma, through atypical urothelial cells and suspicious, to high-grade urothelial carcinoma.
Older thyroid reports may use the terms “follicular lesion of undetermined significance” or “suspicious for follicular neoplasm.” The 2023 Bethesda System replaced these with atypia of undetermined significance and follicular neoplasm.
Why can’t the pathologist always give a definite answer?
A pathologist cannot always give a definite benign or malignant answer, because some samples do not contain enough information. An atypical or suspicious result honestly describes what the sample shows. It does not mean the pathologist was careless or missed something. The most common reasons are listed below.
- The sample is small. A needle biopsy or cytology sample captures only a small part of an abnormal area. The most important part may not be included.
- The cells are damaged. Cells can be crushed, dried, or distorted by heat during removal, which hides the features the pathologist needs to see.
- Inflammation or healing is present. Inflamed and healing tissue can look very much like a tumor under the microscope, especially after an infection, surgery, or radiation.
- Some diagnoses need the whole lesion. For some tumors, the key feature is how the tumor edge meets normal tissue. This can only be judged when the whole lesion is removed.
- More tests are needed. Additional stains, such as immunohistochemistry, or molecular tests may be needed to distinguish two look-alike diagnoses.
What happens after an atypical, suspicious, or uncertain result?
After an atypical, suspicious, or uncertain pathology result, the next step depends on the body part and the exact wording of the report. It also depends on what the imaging or examination showed. In general, the aim is to get more information, so that the uncertain result can be resolved. Common next steps are listed below.
- Repeat sampling. A second biopsy or aspiration may be done, sometimes with a larger needle or from a different spot.
- Removal of the whole area. When a small sample shows a concerning change, removing the whole lesion lets the pathologist examine it all.
- Additional tests on the same sample. The laboratory may add stains such as immunohistochemistry or molecular tests, which can appear later as an addendum to the report.
- Comparison with imaging and examination. Your care team compares the pathology result with scans and clinical findings. A result that matches the imaging is more reassuring than one that does not.
- A second pathology opinion. For difficult cases, another pathologist may review the slides, often one who specializes in that organ. Many reports already state that a colleague reviewed the case.
- Closer follow-up. For some low-risk results, the team may recommend repeat testing after a set interval rather than an immediate procedure.
Each specific result has its own next steps. The diagnosis articles for ASC-US, ASAP, and atypical ductal hyperplasia explain what usually happens for each one.
Does a benign result mean no further care is needed?
A benign pathology result is usually very reassuring, but it does not always mean that no further care is needed. Some benign growths are removed because they cause symptoms, keep growing, or press on nearby structures. A few benign diagnoses also carry a higher risk of cancer later, which can lead to closer follow-up.
A benign biopsy result is also checked against the imaging and the examination. If the imaging looked very suspicious and the biopsy is benign, the team may wonder whether the needle missed the abnormal area. In that situation, a repeat biopsy or removal of the area may still be recommended. You can ask your doctor whether your benign result fits with everything else they found.
Questions to ask your doctor
- Is my result benign, precancerous, or cancer?
- How certain is the pathologist about this diagnosis?
- What does the word “atypical” mean in my report?
- My report says “suspicious.” How likely is it that this is cancer?
- What does “consistent with” or “cannot be excluded” mean for me?
- What does the comment section of my report say?
- Was my sample large enough, or does it need to be repeated?
- Does my result fit with what the imaging showed?
- Will they do more tests on my sample?
- Should the whole area be removed to get a definite answer?
- Has another pathologist reviewed my slides, or should one do so?
- If my result is benign, do I still need follow-up?
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