Why Is Molecular Testing Done After Biopsy?

A biopsy confirms cancer and its type. Molecular testing goes a step further, reading the tumour’s genes and proteins to understand what’s actually driving it. That detail matters because two cancers that look identical under a microscope can behave completely differently, and respond to completely different drugs. The test is what reveals which one you’re dealing with.

According to Dr. Sandeep Nayak, Surgical Oncologist in India, “The biopsy tells us it’s cancer and what kind. Molecular testing tells us how it ticks. We’re looking for specific mutations, the ones a targeted drug can switch off. Without that information you’re treating blind. With it, you can sometimes skip the heavy chemotherapy entirely and hit the exact fault driving the tumour. That’s the whole shift in modern oncology.”

It digs into the tumour’s biology, looking for the specific faults that drive it.

• Driver mutations : Certain genes, when faulty, push a cancer to grow. Testing finds them, and many now have a drug built to target them.
• Receptors : Breast and other cancers are checked for hormone receptors and HER2. Those results decide whole categories of treatment.
• Immunotherapy markers : Some tumours carry signals, like PD-L1, that predict whether immunotherapy will work. Testing flags them upfront.
• Resistance clues : The profile can hint at which drugs a tumour will shrug off, saving the patient from a treatment that won’t work.

This is the information that decides whether robotic cancer surgery alone is enough or whether targeted drugs need to join the plan.

The results don’t just describe the cancer. They actively redirect how it’s treated.

• Targeted therapy : Find a driver mutation with a matching drug, and treatment can hit that exact fault. Far more precise than blanket chemotherapy.
• Sparing chemo : Sometimes the profile shows a targeted drug will outperform chemotherapy. The patient avoids the harsher option altogether.
• Sequencing the plan : The results help decide what comes first, surgery, drugs, or a combination. Order matters, and this informs it.
• A clearer prognosis : The molecular picture often refines the outlook, giving patient and doctor a more honest sense of what lies ahead.

All of this builds on what your biopsy report first reveals, taking that same tissue sample and extracting far more from it.

Dr. Sandeep Nayak is a surgical oncologist with 24 years behind him and a fellowship in laparoscopic and robotic onco-surgery. His diagnostic approach treats molecular testing as a core step, not an afterthought, so treatment is built on the tumour’s actual biology rather than its appearance alone. Every result goes through tumour board review, where surgeons and oncologists read the molecular picture together. That integration is what turns a test result into the right plan.

Molecular detail is where modern cancer care separates itself from the old one size fits all approach. The same diagnosis can need very different treatment depending on what the genes show. Reading that correctly, and acting on it, is what lets a patient get the precise therapy their cancer responds to. Used well, it means better outcomes with less unnecessary treatment.

References

1. Molecular profiling of advanced malignancies — National Library of Medicine
2. Molecular genetic testing and targeted therapy — National Library of Medicine

Disclaimer: This blog is for informational and educational purposes only and is not a substitute for professional medical advice or diagnosis.