| Myoepithelial cells possess contractile properties and exhibit a dual epithelial and smooth muscle phenotype. Although they are an important component in many salivary gland tumors, salivary gland carcinomas displaying exclusively myoepithelial differentiation (myoepithelial carcinoma, MEC for short, or malignant myoepithelioma) are considered rare. Actually The incidence of MEC in the salivary glands is no more than1%. Besides its complex morphologic and immunophenotypic expression, MEC is highlighted by its high grade with recurrence and frequent metastasis. Till now,there are no discernible evidences showing any histologic features or tumor parameters (size, site, growth pattern and architecture, pattern of infiltration, cell type, and etc) that correlate clearly with its behavior and prognosis. Its clinical biological behavior and prognosis are actually unknow. As far as the treatment of MEC is concerned, there is also limited experience.The aim of this retrospective study was to describe the clinicopathologic features of myoepithelial carcinoma, analyze the treatment outcomes, measure the intratumoral microvessel density (iMVD); and the relationships between several pathologic parameters,iMVD, and the outcomes are also of our interest. Clinical, pathologic and follow-up information of14patients, consecutively diagnosed and treated in our institution during a11-year period, was collected. Hematoxylin and eosin-stained slides of all the cases were retrived and reviewed. The formalin-fixed and paraffin-embedded specimens were obtained and consecutively cut into4-μm thick sections; and iMVD was measured by determining the expression of CD31in those xsections. After this, the relationship between them was investigated using partial least squares method. With a painless swelling being the most common complaint and a sex ratio being1:1, the mean age of the patients was47.3years, ranging from14-80years. Minor salivary gland involvement (71%, n=10) was more common than major salivary gland involvement (29%,n=4). Only4cases presented with early-stage disease (stage Ⅰ or stage Ⅱ, according to the7th edition of the AJCC staging manual), the rest were all with locally or regionally advanced disease (stage Ⅲor stage Ⅳ) at diagnosis. Generally, four cell types were observed:epithelioid, plasmacytoid, clear and spindle cells. A variety of growth patterns was observed, with a diffuse sheetlike arrangement of tumor cells being the most common pattern. Infiltration into normal tissues by tumor cells was present in all cases. Bone invasion, blood vessels and perineural invasion were seen in some cases.a comedo-like necrosis was present in2cases. Myxoid matrix and ductal structures were rarely observed. And the iMVD of tumors ranged from40-68per0.36mm2. Surgery was the primary treatment modality for all patients with a recurrence rate of25%. Postoperative radiation and neck dissection were performed in selected cases. And postoperative radiation seemed to play a role in local control in our study. However, no significant correlation was found between iMVD and several pathologic parameters and treatment outcomes; and the necessity to obtain more reliable results by enlarging the sample size is also obvious. |
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