Nuclear Medicine & Radiation Therapy

Acinic Cell Carcinoma of the Parotid Gland: A Rare Case

Abstract

Rajeev Kumar*, Yasmin Nasir, Arunav Kumar and Rajesh Kumar Singh

Acinic cell carcinoma of parotid gland is defined by parotid neoplasm with at least some serous acinous differentiation. It is one of the rare malignancies of parotid (3–11% of adult parotid neoplasm) with very unpredictable clinical behavior in nature. Close differentials are warthins tumor, oncocytoma, clear cell and mucoepidermoid carcinomas. Surgery is the standard of care in this case. A 22-year-old male patient developed a swelling over the left parotid region in 2018, which gradually increased in size without any difficulty faced to the patient. Fine needle aspiration cytology of the swelling revealed pleomorphic adenoma. The patient underwent surgery in 2018 under general anesthesia at another facility, and no post-operative documents were available with the patient. Over time, the swelling recurred in the same region. The patient sought medical attention at IGIMS, ENT department, where fine needle aspiration cytology of the swelling revealed pleomorphic adenoma once again. Magnetic Resonance Imaging showed a heterogeneous mass involving both the superficial and deep lobes of parotid. Subsequently, the patient underwent left parotidectomy for the same condition. The post-operative biopsy and immunohistochemistry suggestive of acinic cell carcinoma with cystic and solid patterns. After confirming the absence of metastasis with PET scan, radiation therapy was recommended due to the recurrence involving the deep lobe. Acinic cell carcinoma is initially considered benign but later reclassified as malignant due to its metastatic and recurrence capability. It commonly affects parotids (85% cases) and constitutes 6-16% of major salivary gland malignancies. Its clinical course is uncertain, with better prognosis in pediatric cases. Family history, radiation exposure, and certain genetic transformations are risk factors. Radiological assessments are inadequate for characterization many times. Surgical resection is the main treatment modality. Chemotherapy is ineffective, but adjuvant radiation can be considered. Recurrences are common, but prognosis is generally good. Correct diagnosis is crucial for effective treatment and recurrence prevention.