What is Molecular Pathology?

Molecular pathology is a field focused on the understanding and diagnosis of disease through studying molecules (such as DNA, RNA and proteins) found in parts of the body including organs, tissues, cells and fluids. It is a branch of the larger field of pathology, which is the general study of disease.

Molecular pathology is important for screening patients for common ailments, diagnosing patients with diseases (such as cancer or genetic disorders) and guiding treatment decisions.

Ultimately, molecular pathology helps doctors and researchers look deeper into diseases beyond what can be seen by the eye. 

How is molecular pathology used?

• Cancer diagnosis and treatment
  • Used to identify specific genetic mutations in tumors, select targeted therapies and predict how a cancer may respond to treatment
     
• Genetic and inherited disease testing
  • Allows doctors to detect inherited conditions (such as cystic fibrosis or sickle cell anemia) and screen for genetic risks in individuals or families
     
• Infectious disease detection
  • Employed in testing to detect viruses and bacteria (including COVID-19, HIV and HPV) using DNA or RNA.
     
• Personalized (precision) medicine
  • Applied in tailoring treatments to align with specific changes in an individual’s genetic makeup, allowing for improved effectiveness and reduced side effects
     
• Pharmacogenomics
  • Shows how alterations in genes can affect an individual's response to drug treatments, making it easier for doctors to prescribe the correct medication and dosage for patients

Who does molecular pathology?

• Molecular pathologists
  • Medical doctors specialized in pathology (often with subspecialty training in molecular genetic pathology) who interpret molecular test results and correlate them with disease diagnoses
     
• Clinical laboratory geneticists 
  • Ph.D. or M.D./PhD. professionals with certification who oversee molecular genetics testing in clinical laboratories and assist in test development, quality control and result interpretation
     
• Medical laboratory scientists/technologists
  • Bachelor's- or master's-level lab professionals trained in molecular diagnostic techniques who perform molecular tests under the supervision of a pathologist or geneticist
     
• Research scientists
  • Ph.D.s or postdocs working in academic or industry research settings who study the molecular basis of diseases to discover biomarkers or develop new diagnostic tools

What are some common molecular pathology tests?

• Polymerase chain reaction (PCR)
  • Amplifies small segments of DNA or RNA so they can be easily analyzed
  • Used for detecting infectious agents (such as COVID-19, HPV and HIV) and identifying mutations in genes.
• Next-generation sequencing (NGS)
  • Sequences large portions of the genome to allow for detection of multiple genetic mutations or alterations at once
  • Used for cancer gene panels (such as BRCA, KRAS, TP53 and BRAF), pharmacogenomic testing and rare genetic disease diagnosis
• Sanger sequencing
  • Method of sequencing smaller DNA regions
  • Used for confirming results from NGS, single-gene disorders and small-scale mutation analysis
  • The first method developed for DNA sequencing
• Fluorescence in situ hybridization (FISH)
  • Binds specific DNA sequences on chromosomes or in cells using fluorescent probes
  • Used for detecting genetic diseases, gene rearrangements and identifying chromosomal abnormalities
• Microarray analysis
  • Examines expression of thousands of genes at once or detects copy number variations
  • Used for gene expression profiling, identifying genetic syndromes and prenatal or postnatal chromosomal analysis
• Karotype
  • Examine a person’s chromosomes
  • Used for detecting large gene rearrangements, extra and missing chromosomes
• Comparative Genomic hybridization
  • Detects chromosome gains and losses
  • Helpful in diagnosis patients with genetic alterations that are associated with developmental or cognitive abnormalities