embryonic rest

embryonic rest

a portion of embryonic tissue that remains in the adult organism. Also called epithelial rest, fetal rest.
References in periodicals archive ?
8] There are four proposed etiologic factors: (1) a carcinoma (usually squamous) with a reactive mesenchymal proliferation (pseudosarcoma), (2) a so-called collision tumor, in which carcinoma and sarcoma arise simultaneously in a specific anatomic site, (3) a malignancy arising in an embryonic rest of epithelial and mesenchymal tissues, and (4) a divergent differentiation of a carcinoma into sarcomatous components, or sarcomatoid carcinoma.
The third theory, that malignancy arises in an embryonic rest of epithelial and mesenchymal tissues, is simply a variation of the collision tumor hypothesis and has the same shortcomings.
It is assumed that it originates in the ectopic cartilaginous embryonic rests of Meckel's cartilage of the first branchial arch.