Induction chemotherapy followed by radiotherapy in primary small cell neuroendocrine carcinoma of the parotid gland: a case report and literature review.

[BACKGROUND] Small cell carcinoma is a highly aggressive neoplasm that commonly arises in the lungs. The occurrence of this tumor in the salivary gland, particularly the parotid gland, is extremely rare, accounting for less than 1% of all cases of malignant parotid gland tumors, and is associated with poor prognosis. Owing to its rarity, there remains no consensus on standardized therapeutic protocols.

[CASE DESCRIPTION] A 58-year-old woman presented with a 4-month history of a progressively enlarging left preauricular mass and was ultimately diagnosed with small cell neuroendocrine carcinoma (SCNC) of the parotid gland. Evaluations including ultrasound, contrast-enhanced computed tomography (CT), and biopsy revealed a left parotid mass with cervical lymph node involvement, no metastases, specific histopathological and immunohistochemical features. Molecular testing showed TP53 and HRAS mutations, a programmed death ligand-1 (PD-L1) expression level of 30%, and the clinical staging was IVA (cT3N2bM0). A novel therapeutic strategy of induction chemotherapy in combination with sequential radiotherapy exhibited substantial therapeutic efficacy for this rare malignancy. We conducted a narrative review spanning 2000-2024 to elucidate the epidemiologic characteristics, diagnostic challenges, therapeutic paradigms, and prognostic determinants associated with parotid gland SCNC.

[CONCLUSIONS] These findings yield valuable insights into the biological and clinical behaviors of this rare parotid gland neoplasm. Furthermore, this work enhances the understanding of the epidemiological characteristics and optimal management strategies for parotid gland SCNC.