Epithelial-Myoepithelial Carcinoma With High Grade Transformation

Abstract

Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland tumor of presumed intercalated duct origin with a low risk of metastasis and mortality. Factors shown to affect behavior include positive margins, vascular invasion, necrosis, and myoepithelial anaplasia. The latter category and dedifferentiated EMCs have been separated on the basis of presumed myoepithelial versus ductal origin, respectively. Three additional cases of typical EMC with transition to high-grade carcinoma are presented. Two of the tumors were stained with CAM5.2, 34betaE12, cytokeratin 14, p63, S100, calponin, smooth muscle actin, and muscle-specific actin. All tumors showed a gradual transition to a high-grade carcinoma from an EMC, each composed of clear cells even in the high-grade regions. One case also showed a discrete area with ductal lumina and another had plasmacytoid morphology. Squamous differentiation was seen in all cases as well. A consistent immunostaining pattern was not noted. Areas with focal lumina were diffusely positive for CAM5.2 only. Areas with clear cells showed patchy S100 positivity only, whereas cytokeratin 14 and 34betaE12-stained squamous pearls. The case with plasmacytoid morphology was diffusely positive for p63. No immunoexpression was noted with smooth muscle actin, muscle-specific actin, or calponin. It was not possible to convincingly separate the high-grade component in these cases into ductal dedifferentiated EMC versus myoepithelial. Recently, there has been a move to abandon the term "dedifferentiation" in favor of "high-grade transformation" in other salivary gland malignancies. We report these 3 such cases, review the literature and propose that these lesions be regarded as "EMC with high-grade transformation."

Oncocytic and Apocrine Epithelial Myoepithelial Carcinoma: Novel Variants of a Challenging Tumor

“…Aside from these named variants, the myoepithelial cells in EMCa may show alterations such as 'ancient change' or spindled morphology with Verocay like palisading or squamous metaplasia (Fig. 3a) [2,[13][14][15]. The oncocytic and apocrine variants are the main focus of this review, but two important variants are summarized here.…”

A Double-Clear Variant of Epithelial-Myoepithelial Carcinoma of the Parotid Gland

“…Immunohistochemistry is useful in recognising the two cell types. The outer myoepithelial cells express p63, which is generally agreed to be a sensitive myoepithelial cell marker in typical EMC [3,4,8]. A traditional marker of myoepithelial cells is SMA, a good indicator of their smooth muscle characteristics.…”

“…A traditional marker of myoepithelial cells is SMA, a good indicator of their smooth muscle characteristics. Other myoepithelial markers, such as S100, calponin and CK14 have been used, although they are less informative than p63 and SMA [3, [8]. Pancytokeratin is not specific, but is considered to be reliable.…”

“…In this case, SMA, S100, and p63 were used in assessing the myoepithelial component and a keratin stain, specifically CK19, to indicate epithelial luminal cells. Roy et al [8]. recommended that dedifferentiated EMC may warrant a more extensive immunohistochemistry panel to fully characterise the disease.…”

“…The prognosis is generally poor in this type of EMC [15]. The use of immunohistochemistry may be helpful in identifying the cell components in both types of high-grade carcinoma; however, the ability to express proteins usually seen in EMC may be lost with loss of differentiation [8]. Due to this fact, the criteria for defining dedifferentiated EMC can be difficult.…”