Dedifferentiation in low-grade mucoepidermoid carcinoma of the parotid gland

Division of Anatomic Pathology, Mayo Clinic, Rochester, MN 55905, USA.
Human Pathlogy (Impact Factor: 2.81). 11/2003; 34(10):1068-72. DOI: 10.1053/S0046-8177(03)00418-0
Source: PubMed

ABSTRACT Mucoepidermoid carcinoma (MEC), a common malignant salivary gland neoplasm, is generally divided into low-, intermediate-, and high-grade types according to the histologic features. To our knowledge, the present report describes the first case of dedifferentiation occurring in a low-grade MEC. A 55-year-old man presented with a biphasic neoplasm of the right parotid gland composed of low-grade MEC and dedifferentiated high-grade anaplastic undifferentiated carcinoma. Immunohistochemically, carcinoembryonic antigen expression was restricted to the low-grade MEC portion. The Ki-67-labeling index was higher in the dedifferentiated component than in the low-grade component. On image cytometric analysis, the low-grade MEC was diploid, whereas the dedifferentiated carcinoma was aneuploid. Although the patient was alive 10 years after the initial diagnosis, the tumor has recurred twice, at 3 months and 7 months after the initial resection. It is important to recognize that dedifferentiation can occur in a low-grade MEC, similar to other low-grade salivary gland carcinomas.

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    • "The immunoprofile of the dedifferentiation/high-grade transformation in salivary gland tumors has been evaluated in many studies (Table 1), however, with variable and therefore inconclusive results, possibly due to the small number of cases. The marker that best distinguished between the transformed and the conventional components was Ki-67, since, in all salivary gland tumors studied, an increased proliferation index was detected in the transformed component when compared to the conventional counterpart [2] [3] [5] [8] [9] [11] [12] [18] [21] [22] [25] [27] [28] [36] [45] [48] [49] [54]. However, a distinct cut-off for the proliferation index that could identify the transformed component has "
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