Salivary Duct Carcinoma of the Parotid Gland Originating from an Epithelial-Myoepithelial Carcinoma: Report of a Rare Case

Abstract

Salivary duct carcinoma (SDC) is a high-grade carcinoma with poor prognosis, especially among various salivary carcinomas. In this study, we report a rare case of SDC of the parotid gland originating from an epithelial-myoepithelial carcinoma (EMC). A 71-year-old Japanese man presented with swelling of the right parotid region and a right facial nerve paralysis for 10 months. He underwent extended total parotidectomy and chemoradiotherapy after the surgery. Histologically, a major part of the tumor was an androgen receptor (AR)-positive, human epidermal growth factor receptor 2 (HER2)-positive, gross cystic disease fluid protein-15 (GCDFP-15)-positive SDC, with a focus of a typical EMC component at the periphery of the lesion. In the transitional area of the two components, inner ductal cells of double-layered ducts showed similar morphology and immunophenotype to SDC. These findings suggest that SDC originated from the inner ductal cells of EMC. Because the tumor included an EMC as a low-grade carcinoma and an SDC as a high-grade carcinoma, we can consider our case as a dedifferentiated carcinoma as well as a hybrid tumor.

Hybrid Carcinoma of The Parotid Gland: A Report of Three Extremely Rare Cases with An Immunohistochemical Analysis and A Review of The Literature

“…If one component of a suspected HC has high proliferative activity and the other has low proliferative activity, carcinoma with HGT should also be considered [32] As both components exhibited similar levels of proliferative activity in all of our cases, we considered that they were not carcinomas with HGT. Recently, Hamamoto et al reported a rare case in which SDC arose from EMC, and they considered that their case should be diagnosed as HC rather than carcinoma with HGT, despite the fact that the two components displayed different proliferative activities and histological grades [23]. Our case 3 might have undergone a similar tumorigenic process to their case.…”

“…Although little information is available, several investigators have suggested that the aggressiveness of HC is determined by the histologically higher-grade component. 23 It would appear that treatments for HC should be targeted at the higher-grade component, but this requires further con rmation in much larger series with longer follow-up periods.…”

“…More than 30 cases of HC have been reported in the English literature (Table 1) [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. However, only 2 cases involving a combination of SDC and squamous cell carcinoma (SqCC) [3] and 3 cases involving a combination of salivary duct carcinoma (SDC) and epithelial-myoepithelial carcinoma (EMC) have been reported [5,16,23]. To the best of our knowledge, it is the rst report about a case of HC involving SqCC and large cell neuroendocrine carcinoma (LCNEC).…”

Coexistence of salivary duct, myoepithelial and epithelial-myoepithelial carcinomas in the parotid gland: a case report and literature review

“…Hamamoto et al. reported that their case had SDC and EMC components and inner ductal cells of double-layered EMC ducts with a similar morphology and immunophenotype to the SDC in the transitional area and suggested that a SDC originated from the EMC inner ductal cells [ 9 ]. We believe that our case was similar; however, the relationship between MC and EMC/SDC is unclear whether hybrid carcinoma or HGT.…”

Epithelial-myoepithelial carcinoma of floor of mouth: A case report of double clear cell variant with immunohistochemical correlation

“…There have been case reports of other types of malignancies like adenoid cystic carcinoma existing along with EMC in salivary glands [6] . Hamamoto et al 2019 published a case report of a ductal carcinoma arising from an existing EMC in the parotid gland [7] . In a study conducted by Gore in 2018, 468 patients were identified with EMC during the time period from 1973-2014.…”