Epithelium

Epithelium is the thin layer of tightly packed cells that covers the body's outer surfaces and lines its internal cavities, organs, and glands. It acts as a protective barrier, controls what passes in and out of tissues, and includes the mesothelium that lines the chest and abdominal cavities. Cancers that arise from epithelial cells are called carcinomas, while mesothelioma arises from the closely related mesothelial lining.

Origin

From the Greek epi- ("upon") and thele ("nipple"), originally coined by Dutch anatomist Frederik Ruysch in the late 1600s to describe the translucent tissue covering the nipple. The term was later generalized in the early 19th century to all surface and lining tissues of the body.

Significance in Asbestos Context

Most asbestos-related cancers arise in epithelial or epithelial-like tissues, the bronchial lining (lung cancer), the laryngeal lining, and the mesothelial lining of the pleura and peritoneum (mesothelioma). When a pathology report describes a mesothelioma as "epithelioid," "biphasic," or "sarcomatoid," it is describing how closely the tumor cells resemble normal epithelial tissue; epithelioid is the most common subtype and generally carries the best prognosis and the widest range of treatment options. Because subtype directly affects both medical decisions and the valuation of a legal claim, the exact epithelial classification on your biopsy report is one of the most important pieces of information in your case.

Example Sentence

Her biopsy showed an epithelioid mesothelioma, meaning the tumor cells still resembled the normal epithelium-like lining of the pleura, which made her eligible for surgical evaluation.

Related Terms

Mesothelium, Epithelioid Mesothelioma, Biphasic Mesothelioma, Sarcomatoid Mesothelioma, Carcinoma, Pleura

Notes

• Ask your oncologist or pathologist to confirm the specific subtype (epithelioid, biphasic, or sarcomatoid) on your pathology report. This affects treatment options, clinical trial eligibility, and prognosis.
• If the diagnosis is unclear or borderline, request a second pathology review at a mesothelioma specialty center (such as an NCI-designated cancer center); subtype reclassification is common and consequential.
• Preserve the original pathology slides and tissue blocks, not just the written report, because future testing (immunohistochemistry, BAP1, MTAP) may be needed to confirm an epithelial origin versus a metastatic carcinoma from another site.
• Distinguishing a primary mesothelioma (from mesothelial lining) from a metastatic carcinoma (from epithelium elsewhere, like lung or ovary) is critical, because it changes both treatment and which exposures are legally relevant.