Epithelioid

Epithelioid describes cells that look like epithelial cells under the microscope, relatively uniform, rounded or polygonal, with distinct borders and a tendency to grow in cohesive sheets, nests, or gland-like patterns. In asbestos-related disease, the word most often appears in pathology reports describing the subtype of mesothelioma a patient has. Epithelioid is one of three recognized mesothelioma cell types, alongside sarcomatoid and biphasic (mixed).

Origin

From the Greek epi- (upon) and thēlē (nipple), the root of "epithelium," the tissue that lines body surfaces and cavities. The suffix -oid means "resembling." Pathologists adopted the term in the 19th century to describe non-epithelial cells that nonetheless take on an epithelial appearance.

Significance in Asbestos Context

When a pathology report labels a mesothelioma as "epithelioid," this is meaningful for both prognosis and treatment. Epithelioid mesothelioma is the most common subtype (roughly 60–70% of pleural cases) and generally carries a better prognosis than sarcomatoid or biphasic disease, with longer median survival and a greater likelihood of being eligible for aggressive treatments such as cytoreductive surgery, pleurectomy/decortication, or extrapleural pneumonectomy combined with chemotherapy or immunotherapy. The subtype also affects clinical trial eligibility. In legal claims, the subtype is documented in the pathology report and is part of the medical record that establishes the diagnosis; defense experts sometimes raise questions about diagnostic certainty, so confirmation by immunohistochemistry (markers such as calretinin, WT-1, CK5/6, and D2-40) is important.

Example Sentence

Her pathology report described an epithelioid mesothelioma with positive calretinin staining, which her oncologist said made her a candidate for surgery followed by chemotherapy.

Related Terms

Mesothelioma, Sarcomatoid Mesothelioma, Biphasic Mesothelioma, Immunohistochemistry, Calretinin, Pleural Mesothelioma

Notes

• Ask your oncologist or pathologist to confirm in writing which subtype (epithelioid, sarcomatoid, or biphasic) your tumor is, and request the percentage of each component if biphasic. This directly affects treatment options and prognosis.
• If your diagnosis was made on a small biopsy, ask whether a second pathology review at a mesothelioma specialty center (such as the International Mesothelioma Program, MD Anderson, or Memorial Sloan Kettering) is appropriate; subtype can sometimes be reclassified on review.
• Preserve copies of the pathology report, immunohistochemistry results, and any tissue blocks or slides. These are central evidence in both medical second opinions and asbestos legal claims.
• Newer pathology guidelines further divide epithelioid mesothelioma into architectural patterns (tubulopapillary, solid, micropapillary, pleomorphic) and nuclear grades that refine prognosis; ask whether your report includes nuclear grading.