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

Abstract

Neuroendocrine tumors (NETs) comprise a heterogeneous group of malignancies from cells derived from the neural crest with neuroendocrine differentiation. Despite the differences in the site of origin, nomenclature, biological behavior, and functional status, NETs share certain ultrastructural and immunohistochemical features. NETs are relative rare tumors with an annual incidence of 5.76 new cases per 100.000 inhabitants and they usually appear in the gastrointestinal tract or in the pulmonary system. Head and neck NETs are uncommon with limited information regarding frequency, most of them showing small cell carcinoma features. NETs that arise from the salivary glands are exceedingly rare. Regardless of their low frequency, it is imperative to accurately differentiate these tumors from the much more common squamous cell carcinomas and from metastasis from another primary tumor due to the completely different therapeutic approaches and prognosis. The diagnosis is based on the recognition of the typical neuroendocrine architecture and immunohistochemical staining and on an exhaustive work-up. Hereby, we report a case of a moderately differentiated NET of the parotid gland that was treated with a complete parotidectomy. We summarize the clues that led to the final diagnosis and major strategies that were employed to manage the patient. We also perform a comprehensive review of the scarce available literature on this topic.

Case Report of a Primary Parotid Large Cell Neuroendocrine Carcinoma

“…For example, TTF-1 is a sensitive marker for lung small cell carcinoma. TTF-1 also helps to rule out Merkel cell carcinoma, where it is consistently negative [9]. S100 is positive in the myoepithelial layer in adenoid cystic carcinoma.…”

Small Cell Neuroendocrine Carcinoma of the Parotid Gland: A Chronicle of Publications Based on the Largest Case Series and a Report of the First Greek Case

“…The diagnosis is based on histological, ultrastructural and immunohistochemical criteria, which may be misdiagnosed in small biopsy samples. For that reason, a large core needle biopsy, rather than an FNA is preferred for diagnosis [4]. A complete work-up is necessary to rule out a metastatic origin of the tumor, since SCCs are much more common in other parts of the body [4].…”

“…For that reason, a large core needle biopsy, rather than an FNA is preferred for diagnosis [4]. A complete work-up is necessary to rule out a metastatic origin of the tumor, since SCCs are much more common in other parts of the body [4]. To this direction radiologic imaging with CT, PET/CT and octreoscan are basic [4].…”

“…A complete work-up is necessary to rule out a metastatic origin of the tumor, since SCCs are much more common in other parts of the body [4]. To this direction radiologic imaging with CT, PET/CT and octreoscan are basic [4]. Chernock, et al reports the difficulties to distinguish primary salivary SCCs from metastases to the salivary glands because morphologic and immunostaining features between cutaneous and salivary NECS may be indistinguishable [10].…”

“…As an exceedingly rare entity in the Head and Neck region, a complete work-up is mandatory in order to define whether this is a primary or a metastatic case [4].…”