Dedifferentiation in low-grade mucoepidermoid carcinoma of the parotid gland

ArticleinHuman Pathlogy 34(10):1068-72 · November 2003with13 Reads
DOI: 10.1053/S0046-8177(03)00418-0 · Source: PubMed
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.
    • "The Ki-67 LI was higher in the “dedifferentiated” component than in the LG component. In the first case, an image cytometric analysis revealed that the LG and HG carcinomas were diploid and aneuploid, respectively [48]. In addition, the second case involved TP53 gene mutations and corresponding protein overexpression [49]. "
    [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.
    Full-text · Article · Jul 2013
    • "Due to this fact, the criteria for defining dedifferentiated EMC can be difficult. It has been suggested that both dedifferentiated EMC and EMC with myoepithelial anaplasia be classified as EMC with high-grade transformation and that they should be treated more radically compared to typical low-grade EMC [16]. In summary, we report a case of a double-clear EMC variant that developed in the parotid salivary gland. "
    [Show abstract] [Hide abstract] ABSTRACT: The hallmark of the histology of epithelial-myoepithelial carcinoma (EMC) is the presence of a regular repetitive mixture of bilayered duct-like structures with an outer layer of myoepithelial cells and inner ductal epithelial cells. Clear cell change in the myoepithelial component is common, but clearing of both cell types, giving an impression of a monocellular neoplasm, is rare. A parotid biopsy was received from an 83-year-old male and subject to routine histologic processing for conventional staining and immunohistochemistry. The encapsulated tumour was composed of sheets of PAS/diastase negative clear cells, separated by fibrous septae. The clear myoepithelial cells were positive for S-100 protein, SMA, and p63 and negative for CK19 and surrounded CK19-positive luminal cells. It is important to utilise immunohistochemistry to differentiate this tumour from others with a similar histologic pattern. Information about the behaviour of the double-clear EMC is limited since there are few cases reported.
    Full-text · Article · Mar 2012
    • "The term HGT is preferred in this case since the tumor was recognizably of epithelial and, specifically, salivary gland origin, rather than showing true dedifferentiation, which arguably requires loss of a clear cut line of differentiation. HGT in a salivary carcinoma has previously been described mainly in adenoid cystic carcinoma [11], but has also been seen in EMC [12], MEC [13], acinic cell carcinoma [14] and PLGA [15]. Like most salivary carcinomas with HGT, this tumor appeared to have more aggressive behavior with early recurrence and radiologic evidence of metastatic disease. "
    [Show abstract] [Hide abstract] ABSTRACT: Hyalinizing clear cell carcinoma (HCCC) is a rare, low-grade salivary gland tumor with clear cells and hyalinized stroma. Prognosis of HCCC is excellent with few cases metastasizing to the lymph nodes and lung. We present a case of a 61-year-old male with recurrent HCCC on the base of tongue. Histologic examination revealed sheets of clear and eosinophilic cells with a background of a myxoid-like matrix. In addition, large, bizarre malignant cells, focal necrosis, and atypical mitotic figures were identified. By immunohistochemistry, the clear cells were positive for CK18, EMA and vimentin, focally positive for CK7 and CD10, but negative for p63, HMWK, SMA and calponin. A metastatic renal cell carcinoma was considered a possibility but the tumor was called "poorly-differentiated carcinoma, NOS". The patient underwent primary radiotherapy. A recurrence was identified at 10 months follow-up. A biopsy of the recurrent tumor showed clear cell differentiation and a predominant cribriform pattern with focal cords of eosinophilic cells invading the stroma. In contrast to the original tumor, no mitotic figures, atypia or necrosis were identified. The combination of lower grade and different architectural patterns appeared markedly different than the previous biopsy and the immunohistochemical pattern was also different. The recurrent tumor showed diffuse positivity for p63 and HMWK. It was negative for CD10, vimentin, SMA and calponin. Fluorescence in situ hybridization (FISH) analysis was positive for rearrangement of the EWSR1 gene in both samples, confirming that this represented a recurrence of the same tumor. It also confirmed that the initial tumor was a HCCC with high-grade transformation.
    Article · Feb 2012
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