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

PTEN Deregulation Mechanisms in Salivary Gland Carcinomas

Among the tumour suppressor genes that affect critically cell functions and homeostasis, phosphatase and tensin homolog deleted in chromosome 10 (PTEN- gene locus: 10q21) regulates the PI3K/Akt/mTOR signalling pathway. PTEN is deleted, mutated or epigenetically hyper-methylated in a variety of human solid malignancies. Salivary gland carcinomas (SGCs) belong to the head and neck carcinomas (HNCs) super category of solid malignancies. Histo-pathologically, they demonstrate a significant diversity due to a variety of distinct and mixed subtypes. Genetically, they are characterized by a broad spectrum of gene and chromosomal imbalances. Referring specifically to suppressor genes, PTEN deregulation plays a critical role in signaling transduction in the corresponding SGC pre- and malignant epithelia modifying the response rates to potential targeted therapeutic strategies. In the current review, we explored the role of PTEN deregulation mechanisms that are involved in the onset and progression of SGCs.

Small Cell Neuroendocrine Carcinoma of the Parotid Gland: An Uncommon Example of Incompletely Encapsulated Tumor Including S100 Protein-Positive Clear Cells

Small cell carcinoma is rare in salivary glands and has recently been termed small cell neuroendocrine carcinoma. We herein describe an uncommon example arising in the parotid gland. The patient was a 75 yearold Japanese male who had swelling in the right parotid area. He underwent a superficial lobectomy and, after a histological diagnosis was made, a total parotidectomy. Histologically, the tumor had a thick hyalinized capsule that was incomplete, beyond which the tumor invaded into the surrounding parotid parenchyma. The tumor consisted of typical small basophilic cells intermingled with bland clear cells, between which a gradual transition was observed both inside and outside the capsule. Small basophilic cells were immunoreactive for chromograninA as well as synaptophysin, while clear cells were positive for S100 protein. The Ki-67 labeling rate reached 30-40% at the high points of small basophilic cells, but clear cells were minimally labelled. The present case was considered a dedifferentiated carcinoma of the parotid gland, possibly with acinic cell carcinoma as a precursor. This tumor could also be considered a "mixed exocrine-endocrine carcinoma," which may explain the histogenesis of neuroendocrine carcinomas in non-endocrine organs that are not included in the diffuse (dispersed) neuroendocrine system, such as the parotid gland.

Impact of Amplified Oncogenes on Salivary Gland Carcinomas

In normal epithelia, proto-oncogenes regulate critical intra- or intercellular functions, including cell growth and proliferation, apoptosis, and signaling transduction from the cell periphery (extracellular space) to the nucleus mediated by different pathways. Oncogenes are the mutated or amplified forms of the corresponding proto-oncogenes that are crucially involved in cell neoplastic and malignant transformation during carcinogenesis. Salivary gland carcinomas (SGCs) demonstrate a variety of histogenetic types. They are characterized by a broad spectrum of chromosomal and gene alterations. In particular, amplifications in specific genes [human epidermal growth factor receptor 2 (HER2), human epidermal growth factor receptor 4 (HER4), epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), Mouse double minute 2 homolog (MDM2), androgen receptor (AR), programmed death (ligand 1 (PD-L1), neurogenic differentiation factor 2 (NEUROD2), phosphatidylinositol 3,4,5-trisphosphate-dependent RAC exchanger 1 protein (PREX1), cyclin-dependent kinase4/6 (CDK4/6), proline-rich acidic protein 1 (PRAP1), kell antigen system (KEL), glutamate receptor subunit epsilon 2 (GRIN2D), Ewing sarcoma RNA-binding protein 1 (EWSR1), MYC proto-oncogene (MYC)] combined or not with chromosomal numerical imbalances (aneuploidy/ polysomy/monosomy) form different genetic signatures affecting the response to monoclonal antibody-based, oncologicaly targeted regimens. Different SGC histotypes demonstrate specific combinations of mutated/amplified genes that modify their clinicohistological features. In the current molecular review, we present the most important amplified oncogenes and their impact on the biological behavior of SGCS.

Cystic Salivary Duct Carcinoma Penetrated by Facial Nerve

Salivary duct carcinoma is a rare malignant salivary gland tumor that mainly has solid features. When it occurs in the parotid gland, it can invade the facial nerve and cause facial nerve paralysis. However, in our case, the salivary duct carcinoma exhibited cystic features on computed tomographic imaging, and the facial nerve passed through the cyst. Total parotidectomy with level-I to -III dissections was performed and nerve passing through the tumor was sacrificed. The patient received postoperative radiotherapy and was clinically and radiologically followed-up for every 3 months. Recurrence or distant metastasis was not reported. To the best of our knowledge, this is the first case involving a salivary duct carcinoma with cystic features and facial nerve invasion. Here, we report a first case of cystic salivary duct carcinoma of the parotid gland which uncommonly undergo cystic change and penetrated by facial nerve and successfully resected without causing facial nerve injury.

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.

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

Few reports have described two or more histologically-distinct carcinoma types within the same salivary gland. A 62-year-old man presented to our hospital after detecting a mass in the right parotid gland. Computed tomography revealed a tumor (5.1 × 5.0 cm) within the right parotid gland. Tumor resection with lymph node dissection was performed. The proliferation of three morphologically-different tumor cells was demonstrated on histopathologic examination (salivary duct carcinoma [SDC], myoepithelial carcinoma and epithelial-myoepithelial carcinoma [EMC]). The shape of the inner layer of cells in the EMC was similar to the SDC. Specifically, it appeared that the cells were a mixture of the two tumors with reciprocal transfer in the same area. Immunohistochemical staining showed that the SDC cells and the EMC inner cells were positive for AR, HER2 and p53. Thus, we suggest that our case represented a high-grade transformation.