The practice of pathology and its role in cancer care has changed significantly in the past decade. In the olden days, it was limited to a microscope and a few special stains. Immunohistochemistry (IHC) arrived after that to advance diagnosis and treatment capabilities.
The current treatment landscape is ever so changing – the era of chemotherapy changed to an era of precision medicine / personalized medicine. “One size fits all” (the approach of chemotherapy) is no longer valid. Each tumor is unique in its own genetic/molecular subtypes. Identifying driver mutation which drives the growth of cancer predominantly and thus also becomes a target for treatment is the present focus of cancer research. The best example is lung cancer. In the past, the major types of lung cancer (on basis of microscopy and IHC) used to be adenocarcinoma, squamous cell carcinoma, and small cell carcinoma. Presently, it’s important to subtype lung Adenocarcinoma into EGFR/ ALK/ ROS1 driven. Specific drugs are available to target these mutations and they have proven to be superior to chemotherapy in controlling cancer. These mutations can be detected in tumor biopsy samples by specialized tests like PCR (Polymerase chain reaction), FISH (Fluorescence in-situ hybridization), etc. Detecting such biomarkers has revolutionized the treatment outcomes in advanced lung cancer. In few cases where a biopsy cannot be done (which is the case with few patients), these mutations can be detected in tumor cells that are shed into blood (called circulating tumor DNA / circulating tumor cells) by an advanced test called Liquid biopsy.
Advances happened in the diagnostic realm of hematologic malignancy also. Subtyping of Acute and chronic leukemias is important for accurate treatment. This is possible with a technique called FACS/ Flow cytometry. This has now become a standard test that should be done before embarking on treatment. Further risk stratification of these leukemias and lymphomas are sometimes important and this is achieved with FISH/PCR/ Karyotyping.
These advances in pathology have made it possible to accurately subtype the major types of cancer and have heralded the era of personalized medicine in oncology. Pathology has truly become the Final Diagnosis.
Dr. G VeniPrasanna,
Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam.