Understanding Your Lung Cancer Pathology Report

A pathology report is a document written by a pathologist detailing the characteristics of cells and tissues obtained during a biopsy or surgery. By examining the samples under the microscope, the pathologist can determine if the cells are benign (not cancerous) or malignant (cancerous).

If there is cancer, the pathology report can provide details about the size, shape, and appearance of the cells. The information can then be used to stage the disease, direct the appropriate treatment, and predict the likely outcome (prognosis). The report may also include genetic test results to determine whether the cancer cells have treatable mutations that respond to newer targeted therapies.

Reading a pathology report can be confusing, but it helps to understand as much as you can so that you can make more informed decisions. Pathology reports can vary from one lab to the next but have similar parts and layouts.

Patient Information

The pathology report opens with basic information about you, as well as an overview of providers and relevant dates. The report will typically list:

  • Your name
  • Date of birth
  • Age
  • Sex
  • Name of the referring doctor who ordered the test
  • Names of other doctors being copied on the report
  • Date and time when the specimen was collected
  • Date and time when the specimen was received by the lab
  • The address of the lab

The pathology report also contains a case number issued by the lab. It is important to note that this is not the same reference number used by your health insurance company.

Specimens Received

The word specimen refers to any tissue or fluid sample sent to the lab for evaluation.

In this section of the pathology report, the pathologist will outline what type of sample was received and from which part of the body the sample was taken. If lung cancer is suspected, the submitted specimens may include:

The specimen may be an entire mass or lymph node taken during open surgery. Or, it may only involve a sample of tissues taken during a needle biopsy (in which a hollow-core needle is inserted through the chest into a tumor) or an endoscopic exam (in which a fiberoptic scope is fed through the mouth into the airways).

Along with the type of sample obtained, the pathologist will detail its location with a combination of letters and numbers. Examples include:

  • "R" for right
  • "L" for left
  • "A" for anterior (to the front)
  • "P" for posterior (to the back)
  • "ESS" for entire sample submitted

Your doctor can tell you what these letters and numbers mean when you review the document.

Diagnosis/Interpretation

Most pathology reports cut to the chase by detailing if there is cancer or not. This is usually included under the heading "Diagnosis" or "Interpretation."

In some cases, the diagnosis may precede "Specimens Received." In others, the diagnosis and specimen information will be consolidated under the same heading.

If there is lung cancer, the pathologist will diagnose the type based on the totality of the findings. Among the most common types of lung cancer are:

Not all lung cancers fit into one category. Some small cell carcinomas have areas with squamous cell carcinoma, adenocarcinoma, or large cell carcinoma mixed in. They are classified as mixed type or combined small cell carcinomas. These distinctions can help predict how quickly or slowly a tumor will grow and spread.

A tumor might also be described as "not otherwise specified (NOS)," meaning that the pathologist was not able to determine if the tumor was adenocarcinoma, squamous cell carcinoma, large cell carcinoma, or some of the other rarer type of carcinoma.

The pathologist who issued the findings will sign off the report, providing both a name and electronic signature as well as a date.

Gross Examination

The gross examination, also known as the macroscopic examination, describes what the pathologist sees with the naked eye. With respect to lung cancer, the pathologist will provide preliminary information about:

  • Tumor size: The measurements include the largest dimension and the general dimension in centimeters (cm).
  • Tumor margins: This is the measurement of tissue surrounding the tumor following surgical resection.
  • Tumor extension: This details whether the tumor appears to have grown into surrounding tissues.
  • Lymph node involvement: This provides information about whether lymph nodes extracted during surgery have any abnormalities in size, shape, or texture.

A tumor's location can play an important role in differentiating lung cancer types. For instance, cancers that develop in the airways are more likely to be squamous cell carcinoma, while those that develop on the outer edges of the lung are more likely to be adenocarcinoma.

The information provided in the "Gross Examination" section is not diagnostic but outlines abnormalities that help support the diagnosis and characterize the disease.

Microscopic Evaluation

After the gross examination, pathologists will evaluate tissue samples under the microscope in a practice known as histology. This requires them to cut postage-stamp-size "tissue blocks" from the specimen, which can then be frozen, sliced paper-thin, and mounted on glass slides.

There are several important pieces of information that can be derived from a microscopic evaluation:

  • Tumor type: The microscopic exam can differentiate the types of lung cancer based on the size, structure, and organization of cells and whether certain proteins are revealed when the sample is stained. These include protein biomarkers known as TTF-1, p63, and chromogranin.
  • Tumor grade: Also known as histological grading, the evaluation is used to describe how much the specimen cells look like normal cells. Cells that look more normal are described as "well-differentiated," while cells that do not look normal are described as "undifferentiated." In general, tumors are graded as grade 1, 2, 3, or 4, depending on the degree of abnormality.
  • Tumor margins: Also known as surgical margins, the evaluation details whether tissues surrounding the tumor are negative/ "clean" (meaning there are no cancer cells) or positive/"involved" (meaning there are cancer cells).
  • Lymph node involvement: This details whether cancer cells from the tumor have spread to nearby lymph nodes. Microscopic evaluation can detail whether a lymph node is positive or negative for cancer and whether the cancer is localized (limited to the place it started) or regional (affecting nearby organs or tissues).

Molecular Test Results

If lung cancer is positively diagnosed, pathologists will proactively perform molecular testing, also known as genetic profiling, to determine if you have a treatable genetic mutation. These mutations have specific receptors on the surface of the cancer cell that targeted drugs can recognize and attack. Because the attack is focused, it leaves normal cells untouched and causes fewer side effects than other treatments.

The treatable mutations in people lung cancer include:

On the pathology report, the molecular testing results will be listed as either "positive" or "negative" for each treatable gene mutation. It may also include the specific genetic test used to make the diagnosis.

How the Pathology Report Is Used

The pathology report is important to the staging of lung cancer. In some cases, the report can provide some or all of the information needed to stage the disease. At other times, additional tests will be needed, including positron emission tomography (PET) and bone scans, to determine if and how far the malignancy has spread.

The two main types of lung cancer are staged differently:

  • Non-small cell lung cancers like adenocarcinoma, squamous cell carcinoma, and large cell carcinoma are staged based on tumor size, lymph node involvement, and whether metastasis has occurred. The disease is classified into five stages, with stage 0 being the least severe and stage 4 being the most severe.
  • Small cell lung cancers have only two stages—limited stage and extensive stage—with extensive-stage cancers having far poorer outcomes.

Based on the type, stage, and grade of the disease, as well as the molecular test results, doctors can prescribe the appropriate treatment, whether the aim is curative or palliative (intended to extend survival and reduce symptoms).

A Word From Verywell

Although pathology reports can provide valuable information about lung cancer based on standardized criteria and algorithms, they are open to interpretation. If there are inconclusive or borderline results (or you are simply unsure about the findings), it is reasonable to get a second opinion from a qualified pathologist.

If you decide to do so, contact the pathology lab where you will be seeking the second opinion and ask what materials they will need. This may include the original tissue samples and any slides made after your biopsy or surgery.

In the United States, federal law requires pathology labs to keep cytology slides for at least five years and tissue sample embedded on paraffin block for at least two years.

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