Dedifferentiation in low-grade mucoepidermoid carcinoma of the parotid gland.
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.
- SourceAvailable from: Toshitaka Nagao[Show abstract] [Hide abstract]
ABSTRACT: "Dedifferentiation" and/or high-grade transformation (HGT) has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous low-grade adenocarcinoma, myoepithelial carcinoma, low-grade mucoepidermoid carcinoma and hyalinizing clear cell carcinoma, although the phenomenon is a rare event. Recent authors tend to preferably use the term HGT instead of "dedifferentiation" in these cases. HGT-tumors are composed of conventional carcinomas juxtaposed with areas of HG morphology, usually either poorly differentiated adenocarcinoma or "undifferentiated" carcinoma, in which the original line of differentiation is no longer evident. The HG component is generally composed of solid nests, sometimes occurring in cribriform pattern of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli and abundant cytoplasm. Frequent mitoses and extensive necrosis is evident. The Ki-67 labeling index is consistently higher in the HG component. p53 abnormalities have been demonstrated in the transformed component in a few examples, but the frequency varies by the histologic type. HER-2/neu overexpression and/or gene amplification is considerably exceptional. The molecular-genetic mechanisms responsible for the pathway of HGT in salivary gland carcinomas largely still remain to be elucidated. Salivary gland carcinomas with HGT have been shown to be more aggressive than conventional carcinomas with a poorer prognosis, accompanied by higher local recurrence rate and propensity for cervical lymph node metastasis, suggesting the need for wider resection and neck dissection.Head and Neck Pathology 07/2013;
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ABSTRACT: Clinicopathological features, prognosis and therapeutic strategies for mucoepidermoid carcinoma originating in salivary and salivary-type glands of the head and neck are reviewed. We emphasise histopathological aspects, appraise the value of histochemistry, electron microscopy, immunohistochemistry and cytophotometry, and discuss histogenesis and characteristic gene translocations. We additionally consider possible diagnostic difficulties, problems related to histological grading and accuracy of existing literature, and areas of controversy or uncertainty which may benefit from further investigations.Archives of Oto-Rhino-Laryngology 04/2014; · 1.61 Impact Factor
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ABSTRACT: Summary. A case of high-grade epithelial carcinoma arising in a low-grade epithelial-myoepithelial carcinoma of the parotid gland is described. The patient was a 52 year-old male who presented a parotideal lump of approximately 20 mm in diameter and underwent excisional surgery. Histologically a typical low-grade epithelial myoepithelial carcinoma was evidenced and, in its context, an area of 7 x 4 mm showing focal aspects of a high-grade adenocarcinoma. The immunohistochemical pattern of the ductal epithelial cells of the low-grade component was similar to that of the epithelial cells of the high-grade carcinoma. The Ki-67 labelling index of the epithelial-myoepithelial carcinoma was 5%, whereas that of the high-grade lesion was 30%. EGFR, p53 and HER-2 genes seem to play no role in the biological behaviour of the tumour, as well as p16CDKN2A, BRAF, NRAS and C-KIT genes studied with biomolecular methods in both the highgrade and low-grade components. No local recurrence occurred after surgery, but multiple bone, cutaneous and lung metastases were detected 10 months later. The patient died 19 months after diagnosis.European Journal of Oncology 10/2013; 18(2):103-109. · 0.22 Impact Factor