Epithelial Cells — Surface-Lining Tissue Cells

Epithelial cells are specialised biological units arranged in tightly packed, continuous sheets. They form tissue layers known as epithelium, serving essential functions such as physical protection, chemical absorption, cellular filtration, and glandular secretion. These cells are categorised by their physical shape—such as squamous, cuboidal, or columnar—and their arrangement, whether in single layers or stratified formations.

In human oncology, epithelial cells are clinically critical because their genetic alterations give rise to carcinomas, the most prevalent category of cancer. The molecular behaviour, polarity, and structural integrity of these cells change during carcinogenesis, often losing adhesion and gaining the capacity to traverse the basement membrane into adjacent tissues.

Knowing that a malignancy originates in epithelial cells helps clarify the diagnosis and predicts how the disease might behave. Pathologists examine these cells under a microscope to confirm cancer, assess tumour differentiation, and check whether malignant cells have breached local boundaries. Recognising tissue of origin guides oncologists in predicting standard patterns of spread, as carcinomas typically disseminate first through regional lymphatic channels before reaching distant organs. This cellular insight provides the foundation for accurate clinical staging, targeted therapy selection, and personalising follow-up surveillance.

Pathologists evaluate epithelial cells through tissue biopsies, brushings, or fluid cytology. Routine hematoxylin and eosin staining reveals cellular shape and organisation. Immunohistochemistry tests for characteristic epithelial markers such as cytokeratins (including CK7 and CK20) and epithelial membrane antigen (EMA). Genomic profiling may identify specific driver mutations, such as EGFR or KRAS alterations, within the malignant epithelial tissue.

Epithelial cells give rise to carcinomas, representing roughly 80 to 90 percent of all diagnosed cancers. Common forms include adenocarcinoma, which starts in mucus-producing epithelial tissue found in the breast, prostate, colon, and lungs. Squamous cell carcinoma develops in the flat epithelial cells lining the skin, head and neck, and oesophagus. Transitional cell carcinomas emerge in the urothelium of the bladder and kidneys.

Because carcinomas often possess distinct surface receptors, identifying an epithelial origin directs therapeutic choices. Systemic approaches frequently employ platinum-based chemotherapy or antimetabolite agents known to target rapidly dividing cells. If molecular testing reveals targetable alterations, treatments may include tyrosine kinase inhibitors or monoclonal antibodies. In early-stage disease, surgical resection and localised radiotherapy focus on clearing the primary epithelial lesion.