Small cell neuroendocrine carcinoma of the parotid gland

Proceedings of the NASHNP Companion Meeting, March 18th, 2018, Vancouver, BC, Canada: Salivary Neuroendocrine Carcinoma-An Overview of a Rare Disease with an Emphasis on Determining Tumor Origin

Salivary neuroendocrine carcinomas are rare and the overwhelming majority is high-grade. The parotid gland is the most commonly involved site followed by the submandibular gland. Most arise de novo but rare examples occurring as a high-grade transformation of another type of salivary gland neoplasm exist. There is significant morphologic and immunophenotypic overlap with neuroendocrine carcinomas of other sites, especially the skin. Like cutaneous neuroendocrine (or Merkel cell) carcinomas, approximately three-fourths are cytokeratin 20 positive. Cytokeratin 20 positive salivary neuroendocrine carcinomas are often referred to as being of the 'Merkel cell type' since most other non-cutaneous neuroendocrine carcinomas are cytokeratin 20 negative. Salivary neuroendocrine carcinomas may be challenging to separate from Merkel cell carcinomas of the head and neck on pathologic grounds because the latter often metastasize to the parotid gland. Clinical history is often relied upon to separate primary salivary tumors from cutaneous metastases but may not be helpful in all cases. Here we review the clinical, pathologic and molecular features of salivary neuroendocrine carcinomas focusing on high-grade major salivary gland tumors. The difficulty in separating salivary tumors from metastatic Merkel cell carcinoma will be highlighted.

Primary small cell carcinoma of the parotid: Fine needle aspiration and immunohistochemical features of a neuroendocrine variant

Salivary gland small cell carcinoma (SGSmCC) is extremely rare, accounting for less than 1% of salivary gland tumors. A 42-year-old female patient came to the outpatient clinic due to a mass localized in the left submandibular space and that had been growing since 3-4 months. The fine needle aspiration cytology (FNAC) matched with small cell carcinoma (SmCC). As no other focus was detected by computerized tomography (CT), it was accepted as a primary neoplasm of the parotid gland. The histopathological assessment of the excised material and immunohistochemical staining demonstrated a neuroendocrine differentiation of SmCC. No recurrence was observed during the 54-month follow-up period. We believe this to be the second case of SmCC with neuroendocrine differantiation of the parotid glands reported in Turkısh medical literature and will be added to the english database as one of the favorable SmCC cases.

Small cell carcinoma of the salivary gland: a systematic literature review and two case reports

Salivary gland small cell carcinoma is a rare neoplasm, accounting for less than 1% of salivary gland tumours. Little is known about the epidemiologic factors and treatment of this lesion. The authors report two cases and perform a systematic literature search from 1960 to 2011 for articles on salivary gland small cell carcinoma. Once the papers were reviewed, a database was generated to analyse clinical and pathological features, treatments and outcomes, and an attempt was made to identify prognostic factors. Available data were retrieved for 44 cases which fully satisfied the inclusion criteria; the median age was 64.25 years and the male:female ratio was 2.4:1. The parotid gland was the most common site (79.6%). The overall 1-, 2- and 5-year survival rates were 75.3%, 56.4% and 36.6%, respectively. According to the present review, patient age, tumour size, distant metastasis and cytokeratin-20 positive immunostaining were all significant prognostic factors in a univariate analysis. No particular treatment approach appeared to improve survival. This work reinforces knowledge about salivary gland small cell carcinoma's epidemiologic features, and identifies new prognostic markers. The optimal management of this lesion remains controversial.

Small cell carcinoma ex-pleomorphic adenoma of the parotid gland

Small cell carcinoma (SCC) is a high-grade malignancy usually encountered in the lungs but also seen in almost any site including the salivary glands. SCC is important to recognize because it often metastasizes widely and is treated with systemic chemotherapy. Carcinoma ex pleomorphic adenoma is a malignant epithelial neoplasm arising in a pre-existing benign mixed tumor (i.e., pleomorphic adenoma, PA). While virtually any salivary carcinoma can arise from a PA, to our knowledge SCC ex-PA has not been described. We report a case of a woman presenting with fullness of the right neck and a parotid gland mass. The tumor was resected and evaluated grossly, by light microscopy, and by immunohistochemistry. Grossly, a 1.6 cm well-circumscribed nodule was identified within the parotid. Microscopic examination revealed foci of SCC associated with high-grade adenocarcinoma, in the background of a PA. The SCC was immunoreactive for cytokeratin in a dot-like pattern and neuroendocrine markers synaptophysin and CD56. Despite the focal nature of the SCC in the parotid, a pure SCC metastasis was present in one neck level II lymph node. The patient was free of disease with 8 months of follow-up. Our case illustrates that: (1) although rare, in the salivary glands SCC may arise from lower grade neoplasms including PAs; (2) SCC ex PA may metastasize as pure SCC even if the primary SCC component was focal; (3) adequate sampling of PAs is crucial to prevent missing a rare SCC that must be treated with chemotherapy.

[Neuroendocrine carcinoma of the parotid gland]

INTRODUCTION

Neuroendocrine carcinomas are rarely observed in the parotid gland.

CASE REPORT

A 65-year-old woman with an uneventful history was hospitalised for a tumor in the left parotid gland which had progressed for 8 months. The clinical manifestations and the radiological findings were in favour of a malignant process involving the parotid gland. Search for local and regional extension was considered to be negative. The surgical procedure was very difficult but enabled conservative resection of the tumor by total parotidectomy. Pathology results were in favour of a neuroendocrine carcinoma of the parotid gland. External radiotherapy was proposed, but interrupted by the patient after having received 40 Gy. After a 13 month follow-up, the patient was in good general condition without any sign of relapse or metastasis.

CONCLUSION

Parotid neuroendocrine carcinomas are rare but need to be individualized owing to their poor prognosis with frequent occurrence of hepatic and pulmonary metastasis.

Metastatic neuroendocrine tumors of the parotid gland

OBJECTIVES

To present 2 cases of neuroendocrine tumors of the parotid gland and to review the clinical presentation, histopathologic, and immunohistochemical findings and treatment of these rare tumors.

STUDY DESIGN

Case series.

METHODS

This study reviews 2 patients who both presented with firm masses in the parotid gland diagnosed as neuroendocrine carcinoma by histopathologic and immunohistochemical examination. The evaluation, diagnosis, and treatment are discussed.

RESULTS

Both patients underwent complete tumor extirpation via a total or subtotal parotidectomy. Both patients received postoperative radiation therapy and chemotherapy.

CONCLUSIONS

Neuroendocrine tumors of the parotid gland are uncommon lesions; however, they have a favorable prognosis as compared to their pulmonary counterparts with early diagnosis and aggressive treatment. Diagnosis is based on the immunohistochemical characteristics of the tumor. Appropriate treatment includes complete surgical excision with postoperative radiation therapy to the parotid bed with the addition of postoperative chemotherapy in patients suspected to have metastatic disease.