Salivary hybrid tumour: adenoid cystic carcinoma and basal cell adenocarcinoma

Hybrid Carcinoma of the Parotid Gland: An Extremely Rare Three Cases with an Immunohistochemical Analysis and a Review of the Literature

Salivary hybrid carcinoma (HC) is defined as when two or more kinds of carcinoma exist at the same location in a single mass. We reestimated and examined three cases of salivary gland HC. Case 1 involved a 76-year-old male. Case 2 involved a 74-year-old female. Case 3 involved a 66-year-old male. Histologically, case 1 involved a combination of salivary duct carcinoma (SDC) and squamous cell carcinoma (SqCC). Immunohistochemically, the former was positive for gross cystic disease fluid protein (GCDFP)-15 and androgen receptor (AR). Case 2 involved a combination of SqCC and neuroendocrine carcinoma. Immunohistochemically the latter was positive for synaptophysin and neural cell adhesion molecule (NCAM). Case 3 involved a combination of SDC and epithelial-myoepithelial carcinoma (EMC). Immunohistochemically, the former was positive for GCDFP-15 and AR, whereas the inner cells of the latter were positive for cytokeratin 7, and the outer cells of the latter were positive for actin. Because of the transitional zone between SDC and EMC, it was speculated that high-grade SDC arose from low-grade EMC.

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

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.

An Unusual Hybrid Salivary Gland Tumor: Molecular Analysis Informs the Potential Pathogenesis of This Rare Neoplasm

Background

The presence of two or more tumor entities growing in adjacent locations within the salivary gland is very rare, and pathologic studies on such lesions are limited, particularly those with molecular information. Since the clinical history and imaging studies are usually nonspecific, accurate diagnosis and clinical management largely depend on a thorough histological examination.

Methods and Results

We describe a 71-year-old man with an unusual case of hybrid salivary gland tumor composed of mucoepidermoid carcinoma and basal cell adenoma. Molecular analysis revealed differing driver genetic alterations in each component.

Conclusions

Hybrid salivary gland tumors are rare, and their pathogenesis is controversial. The combination of mucoepidermoid carcinoma and basal cell adenoma has not been previously described. While malignant transformation of adenoma to carcinoma seems plausible, gene sequencing was more suggestive of their independent derivation. Key to appropriate surgical management is identifying the more aggressive component, ideally at the time of intraoperative consultation.

Salivary gland hybrid tumour revisited: could they represent high-grade transformation in a low-grade neoplasm?

Salivary gland hybrid tumour, first described in 1996, is a very rare neoplasm for which exact morphological criteria have not been universally agreed upon. In contrast, the concept of high-grade transformation (HGT) in salivary neoplasms has been widely accepted during the last decade, and the number of reported cases is rapidly increasing. A review of the literature revealed 38 cases of hybrid tumour reported in 22 publications. During approximately the same time period, well over 100 cases of HGT in salivary neoplasms have been reported. There are important histological similarities between hybrid tumours and salivary tumours with HGT. In the latter, containing one tumour component of low-grade malignancy and the other of high grade, the two tumour components are not entirely separated and appear to originate in the same area. Virtually, all cases reported as hybrid tumour had no clear lines of demarcation between the two tumour types. We are inclined to suggest that most of the 38 cases of hybrid tumours described in the literature would today better be called tumour with HGT rather than hybrid tumour. The relative proportion of the two components may vary, and the high-grade component is sometimes very small, which emphasises the importance of very generous sampling of the surgical specimen. The molecular genetic mechanisms responsible for HGT, including what used to be called hybrid tumour, remain largely unknown. Abnormalities of a few genes (including p53, C-MYC, cyclin D1, HER-2/neu) have been documented. As insufficient data exist on gene abnormalities in these lesions, conclusions as to whether or not they have a common origin and which mechanisms are involved in transformation cannot be drawn. Due to the small number of cases reported, many of which lack follow-up details; indicators of prognosis of hybrid tumours are not available, but their behaviour seems to be similar to that of tumours with HGT, i.e. an accelerated aggressive course. HGT of salivary gland neoplasms greatly influences macroscopic and microscopic evaluation of the specimen but also, given the high incidence of metastases and morbidity, carries significant treatment implications.

Basal cell adenocarcinoma and Basal cell adenoma of the salivary glands: a clinicopathological review of seventy tumors with comparison of morphologic features and growth control indices

Basal cell adenoma and basal cell adenocarcinoma represent uncommon basaloid salivary gland neoplasms that show marked morphologic similarity. We wished to compare clinical outcome and morphologic features as well as growth and proliferation associated markers for both neoplasms. We reviewed the pathologic features of 70 neoplasms diagnosed as basal cell adenoma or basal cell adenocarcinoma. Observations included maximum mitotic activity and presence or absence of invasion into surrounding normal tissues as well as immunohistochemical studies for Ki-67, caspase 3, p53, and bcl-2. Establishing malignancy on the basis of invasion into surrounding benign tissues, 41 basal cell adenomas and 29 basal cell adenocarcinomas were identified. For tumors with follow-up, recurrence rates were 6.7 % for basal cell adenoma and 16.7 % for basal cell adenocarcinoma. One patient with basal cell adenocarcinoma had distant metastases and died of disease. Overall basal cell adenocarcinomas showed significantly higher values for growth and proliferation markers compared to basal cell adenomas. Salivary gland basal cell adenoma and basal cell adenocarcinoma show morphologic similarity. Basal cell adenocarcinoma can exhibit a locally aggressive behavior and has potential metastatic behavior. The overall mitotic rate and Ki-67 expression were higher in basal cell adenocarcinoma compared to basal cell adenoma, but overlap between the results of these observations in each tumor did not allow for accurate diagnosis or prediction of outcome in individual cases. We conclude that morphologic observation of local tissue invasion is the best marker for separating basal cell adenoma from basal cell adenocarcinoma.

An unusual cribriform variant of salivary basal cell tumours: a clinicopathological study of 22 cases

AIMS

To clarify the clinicopathological characteristics of salivary basal cell tumours exhibiting cribriform architecture, and to discuss the differential diagnosis of these tumours with regard to adenoid cystic carcinoma (AdCC).

METHODS AND RESULTS

Eighteen basal cell adenomas (BCAs) and four basal cell adenocarcinomas (BcACs) with at least a 10% area of cribriform morphology were collected, and the histological and immunohistochemical features were evaluated. The majority of tumours showed the typical histological patterns of basal cell tumours, in addition to cribriform architecture. In some areas, the periphery of cribriform nests had a palisade arrangement. Focal capsular infiltration, but not invasion of surrounding normal tissue, was detected in 14 of 18 BCAs. The capsules were absent or incomplete and mainly accompanied by focal invasion in BcACs. Cystic degeneration was observed in 12 of 22 tumours. The Ki67 labelling index of basal cell tumours was significantly lower than that of cribriform AdCCs (P = 0.001). All patients had a good outcome after a follow-up of 15-96 months.

CONCLUSIONS

The cribriform variant shares most of the clinicopathological features of conventional basal cell tumours. Admixtures of cribriform and trabecular or tubulo-trabecular subtypes, peripheral palisading, cystic changes, non-invasive or low-grade invasive growth patterns and a low Ki67 labelling index may be useful for distinguishing basal cell tumours with a cribriform architecture from AdCCs.

Hybrid carcinoma of the parotid gland: report of a case (epithelial-myoepithelial carcinoma and salivary duct carcinoma) and review of the literature

Hybrid tumors of salivary glands are rare neoplasms. We describe a case of a 74-year-old male with a hybrid carcinoma composed of epithelial-myoepithelial and salivary duct carcinomas of the right parotid gland. The presence of two components was verified by differential immunohistochemical staining. The tumor was surgically resected. There has been no evidence of recurrence to date. To our knowledge, this is the first report of a hybrid carcinoma composed of epithelial-myoepithelial and salivary duct carcinomas of the parotid gland in Japan.