The distribution and morphology of myoepithelial cells in one case of normal breast and in 4 cases of lobular carcinoma in situ (LCIS) were studed by immunoperoxidase and immunofluorescence with anti-actin antisera and by electron microscopy. The actin-rich cells appeared to lay flattened on the basement membrane, or perpendicular to it, or appeared dislodged toward the center of the neoplastic ductules in the different cases. It is proposed that the presence of actin-rich cells inside the neoplastic aggregates represents a process of colonization of lobular carcinoma by myoepithelial cells dislodged from the basement membrane; a differentiation of some neoplastic cells toward myoepithelial elements might also be taken into consideration. The features here described could identify a preinvasive stage of LCIS.
We report and discuss a case consisting of 2 lesions that developed at different times in the same parotid gland. Although the first lesion showed morphologic features similar to those of the benign lymphoepithelial lesion, a monotypic IgM/K pattern was also revealed by the immunoperoxidase method in its lymphoid infiltrates. Thus, on cytologic grounds, the first lesion was classified as lymphoplasmacytic immunocytoma (according to Kiel criteria). In the second lesion, which recurred 3 years later, the prominent feature was a marked predominance of plasma cells with the same monoclonal IgM/K as the preceding lymphoma. These findings suggests that a B-lymphomatous cell monoclone may undergo morphologic maturation along the lineage of its competence. Secondly, they indicate that every case of benign lymphoepithelial lesion of the salivary glands should undergo thorough immunologic evaluation to exclude the possibility of signs of precocious lymphomatous transformation.
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