Primary Neuroendocrine Tumor of the Parotid Gland: A Case Report and a Comprehensive Review of a Rare Entity

Fine-needle aspiration cytology of palisading adenocarcinoma: The first cytology report of a newly described salivary gland neoplasm

Here, we report the first cytology findings of the newly characterized entity, palisading adenocarcinoma of the salivary gland, diagnosed in the sublingual gland of a 61-year-old female. The liquid-based cytology showed a moderately cellular aspirate containing three-dimensional clusters and trabeculae of tumor cells of various sizes. The cells had dark ovoid nuclei, finely granular chromatin, inconspicuous to punctate nucleoli, and ample cyanophilic cytoplasm with indistinct cell borders. In conventional smears, the cells displayed frequent crush artifacts and anisonucleosis resembling endocrine-type atypia. The background was clean, devoid of secretions, and contained singly dispersed tumor cells with stripped nuclei. Interestingly, concentrically laminated globules of extracellular matrix surrounded by the tumor cells were identified. Mitotic figures and tumor necrotic debris were absent. The cytologic findings correlated with the histologic findings of the excision specimen. The cytologic differential diagnosis and tumor grading of palisading adenocarcinoma were briefly discussed.

Metastatic Neuroendocrine Tumors to Parotid Gland: Where Do They Come From?

Background. Metastasis to parotid gland occurs mostly from skin cancers of the head and neck region. Metastatic neuroendocrine tumors to the parotid gland are rare and not well studied so far. In this study, we undertook a retrospective review of secondary neuroendocrine tumors of the parotid diagnosed in our institution. The most common entities, primary tumor locations, their clinical presentations and histopathological features were analyzed. Methods. Cases of secondary neuroendocrine tumors to parotid diagnosed from August 1995 to Jan 2021 were retrieved from our institution's pathology databases, and their clinicopathological features were reviewed. Results. About 29% (120 of 420 cases) of parotid neoplasms were malignant, including 70 cases of parotid primary malignant tumors and 50 cases of metastases to parotid glands. Among metastatic tumors to the parotid glands, squamous cell carcinoma and melanoma of the head and neck region together accounted for about 78% of the cases. Only 11 of 50 metastatic tumors to the parotid were neuroendocrine carcinomas (22%). The most common primaries were poorly differentiated neuroendocrine carcinoma of lung (5 of 11 cases), including 4 cases of small cell carcinoma and one case of large cell neuroendocrine carcinoma. The second most common secondary tumor was Merkel cell carcinoma (4 of 11 cases, 36%) including one case of direct invasion from overlying skin. Medullary carcinoma of the thyroid comprised the rest of the metastases to the parotid (2 of 11 cases, 18%). Conclusion. Our results show that metastatic neuroendocrine carcinomas to the parotid gland account for about 22% of all metastatic tumors to the organ. Lung is the most common primary neuroendocrine carcinoma location. It is not uncommon for metastatic neuroendocrine carcinoma to present as the first sign of systemic clinical manifestation. Merkel cell carcinoma is the second most common entity that metastasizes to parotid, followed by medullary carcinoma of the thyroid.

Primary Large Cell Neuroendocrine Carcinoma of the Parotid Gland. Report of a Rare Case

Primary neuroendocrine carcinomas of the salivary glands are very rare neoplasms that present light microscopic, ultrastructural, and immunohistochemical features of neuroendocrine differentiation. Twelve cases have been published in the English language literature. We describe the pathologic features of a case of primary large cell neuroendocrine carcinoma of the parotid gland in a 91-year old male and summarize the immunophenotype of previously reported LCNECs of the major salivary glands. It is concluded that primary LCNEC of the salivary glands presents as a high-grade undifferentiated carcinoma, whose diagnosis may be hindered by its rarity and non-specific light microscopic features. A high level of awareness, immunohistochemical staining for neuroendocrine markers synaptophysin and CD56, and a thorough diagnostic work-up in order to exclude metastasis from a primary neuroendocrine carcinoma will allow its diagnosis.