Visual inspection of the gross specimen and tissue staining are two important aspects of assessing tumors in the pathology lab and are briefly summarized in the following section.
Gross examination is the visual macroscopic inspection of the tumor, without the use of a microscope. All anatomic structures present, and the tissue specimen’s size, color and consistency, are recorded. Gross examination helps the pathologist determine the size of the specimens to dissect and assess. Histologic sections that best demonstrate the features seen at gross description, including assessment of margins (if applicable) are taken during gross examination. Inking of margins also is performed at gross examination. The process provides important diagnostic information used for staging and prognosis, and a picture may be taken as part of the record.
Histology is the microscopic appearance of stained cell and tissue structures of a specimen. The characteristic histology of cells/tissue is used to identify all of the pathologic processes involving a specimen.
Commonly used histologic stains include:
- Hematoxylin (nuclei) and eosin (cytoplasm) staining (H&E)
- H&E is the standard stain performed for routine examination of tissue under the microscope to form the cornerstone of pathologic diagnoses. Hematoxylin is a dark blue or violet stain that binds to DNA and RNA in the nucleus of cells. Eosin is a red or pink stain that binds to cytoplasmic proteins.
- A wide variety of special stains are available to evaluate pathologic processes, a few of which are quickly summarized below:
- Identification of acid mucins within cells (may be used to facilitate identification of Barrett’s mucosa in biopsy specimens).
- Congo red
- Detection of amyloid within tissue.
- Detection of mucin within neoplasms, supporting classification as adenocarcinoma (e.g. non-small cell lung carcinomas).
- Periodic acid-Schiff
- Detection of glycogen or mucin within neoplasms.
- Trichome stain
- Primarily used to demonstrate collagen and muscle in normal tissue (e.g. detection of increased fibrosis in the liver).
Source: Levine Cancer Institute, Carolinas Healthcare System
Overview of biomarker testing
Biomarkers for risk, diagnosis, prognosis, prediction and response are used throughout the continuum of care in oncology.
Source: Carol J. Farhangfar, PhD, MBA
The field of cancer genetics is focused on the evaluation of important risk markers and inherited disease. Most well-known are markers such as BRCA1 and BRCA2 for inherited risk of breast/ovarian cancer. Other examples include markers for Lynch syndrome (hereditary nonpolyposis colorectal cancer) and Li-Fraumeni syndrome. Individuals with Lynch syndrome have mutations in genes typically involved in repair of DNA (MLH1, MSH2, MLH3, MSH6, PMS1, PMS, and TGFBR2) giving them a much higher likelihood of developing colon cancer as well as other cancers (eg, endometrial, ovarian, pancreatic) at an earlier age. Mutations in the tumor suppressor gene TP53 and CHEK2 may indicate the patient has Li-Fraumeni syndrome, which often affects children or young adults and leads to development of multiple types of tumors in their lifetime.
Whereas histology and morphology are important to determine if a tumor is benign or cancerous, molecular markers can help confirm diagnosis. An example of this is the use of BCR-ABL fusion marker to confirm the diagnosis of leukemia. This marker is also useful for the prediction of response to treatments and to monitor disease. The CA-125 marker is often used to help determine if a mass in the ovaries is potentially cancerous.
Prognostic markers are used to help a physician assess the potential outcome for a patient regardless of treatment. They can help assess the aggressiveness of disease. An example of a prognostic marker is CA19-9 in pancreatic cancer, which can help assess the operability of the tumor and provide insight into potential survival. The expression of CD44 is often associated with a poor prognosis in bladder cancer, whereas expression of cyclin D1 is associated with a better prognosis with lower odds of recurrence.
Predictive markers are used to determine potential for response to a specific treatment. Targeted therapies often use companion diagnostics to direct treatment decisions. These tests use predictive markers to identify which drugs may provide a favorable response for a patient. Examples include the EML4-ALK fusion gene for treatment with crizotinib (Xalkori, Pfizer) in non–small cell lung cancer and BRAF V600E mutation for treatment of melanoma with vemurafenib (Zelboraf, Genentech).
Markers of response are often considered the same as predictive markers. However, with the introduction of circulating tumor DNA tests, it is now possible to monitor response over time, not just before treatment.
Clinical trials assessing utility of biomarkers
Most trials now incorporate assessment of biomarkers. The markers may be used to guide selection of treatment in the study or may be added as correlatives for analysis after the study is completed to learn if there are associations of specific markers to response to treatment. Examples of large multidrug studies using markers to drive treatment choices include:
- ASCO Targeted Agent and Profiling Utilization Registry (TAPUR) study: This prospective, nonrandomized trial will collect information on the antitumor activity and toxicity of commercially available targeted cancer drugs in multiple tumor types (including advanced solid tumors, multiple myeloma, and B-cell non-Hodgkin’s lymphoma) with a genomic variation known to be a drug target. The study will evaluate 18 drugs targeting 44 genes contributed by seven pharmaceutical companies, with cohorts of up to 35 patients defined by tumor type, genomic abnormality and drug. This study, which opened in cancer center networks in Michigan and at Carolinas Healthcare System’s Levine Cancer Institute in March 2016, has the potential to identify new applications of current drugs. Additional drugs/targets are expected to be added as the study continues.
- NCI-Molecular Analysis for Therapy Choice (MATCH) trial: This phase 2 trial will evaluate more than 20 different study drugs or drug combinations, each targeting a specific gene mutation, to match each patient in the trial with a therapy that targets a molecular abnormality in his or her tumor.
Biomarkers and their FDA-approved companion diagnostic test
Others (listed at FDA, List of Cleared or Approved Companion Diagnostic Devices [In Vitro and Imaging Tools])
Abbreviations: ALK, anaplastic lymphoma kinase; BRCA1/2, breast cancer 1/2, early onset; CLL, chronic lymphocytic leukemia; EGFR, epidermal growth factor receptor; FISH, fluorescence in situ hybridization; IHC, immunohistochemistry; KIT, v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog; LSI, locus specific interphase; PCR, polymerase chain reaction; PDGFRB, platelet-derived growth factor receptor-beta; PD-L1, programmed death ligand-1
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