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Acinic cell carcinoma (AciCC) is a rare malignant neoplasm of the salivary glands, predominantly arising from the parotid gland. It is considered a low-grade malignancy, but it has the potential for local recurrence and, rarely, distant metastasis. Early recognition, accurate diagnosis, and complete surgical management are essential to optimize outcomes.
Definition and Classification
Acinic cell carcinoma is a malignant epithelial tumor showing serous acinar differentiation, mimicking normal salivary acinar cells. The WHO recognizes AciCC as a distinct entity among salivary gland malignancies.
Histologically, AciCC may display multiple growth patterns:
- Solid- Microcystic
- Papillary-cystic
- Follicular
These patterns often coexist within the same tumor.
Epidemiology
- AciCC accounts for approximately 2–4% of all salivary gland malignancies.- Predominantly affects middle-aged adults, but can occur in children and adolescents.
- Slight female predilection has been reported.
- Most cases arise in major salivary glands (especially the parotid), with minor salivary gland involvement being uncommon.
Etiology
The precise cause of AciCC is unknown. There is no strong association with tobacco, alcohol, or radiation exposure. Genetic studies have identified occasional chromosomal translocations and alterations in tumor suppressor genes, but these are not yet clinically definitive.
Common Sites
- Parotid gland (most common)- Submandibular gland (rare)
- Minor salivary glands of the palate, buccal mucosa, and lips (uncommon)
Clinical Presentation
- Slow-growing, painless mass in the salivary gland region- Firm, mobile swelling
- Occasional facial nerve involvement if tumor arises in the parotid and invades nearby structures
- Rare pain or discomfort
- Rarely ulceration occurs in minor salivary gland lesions
Because of its slow growth, AciCC may be clinically mistaken for a benign lesion.
Diagnostic Approach
Diagnosis involves a combination of clinical evaluation, imaging, and histopathology:
- Imaging: Ultrasound, CT, or MRI to evaluate tumor extent and detect deep lobe involvement or bone invasion- Fine-needle aspiration cytology (FNAC): Useful for preliminary diagnosis but may be inconclusive
-Incisional or excisional biopsy: Gold standard for definitive diagnosis
- Histopathological examination with immunohistochemistry may show positivity for cytokeratins, DOG1, and amylase, confirming acinar differentiation
Histopathological Features
- Tumor cells resemble normal serous acinar cells- Abundant granular basophilic or eosinophilic cytoplasm
- Round, uniform nuclei with minimal pleomorphism
- Growth patterns: solid, microcystic, papillary-cystic, or follicular
- Low mitotic activity in most tumors
- Perineural invasion is uncommon but may occur in aggressive cases
Management and Treatment
- Surgical excision with clear margins is the mainstay of treatment- Superficial or total parotidectomy depending on tumor location and extent
- Neck dissection is usually not required unless there is clinical nodal involvement
- Adjuvant radiotherapy is reserved for high-grade tumors, positive margins, or recurrent disease
- Chemotherapy has limited role and is typically used for metastatic disease
Prognosis
- Generally favorable, with 10-year survival rates exceeding 90% for low-grade tumors- Local recurrence occurs in 10–20% of cases, often due to incomplete excision
- Distant metastasis (lungs, liver, bone) is rare but more likely in high-grade variants
- Long-term follow-up is recommended, as late recurrences have been reported
Role of Dental and Medical Professionals
Dental professionals may encounter minor salivary gland tumors or parotid swellings:
- Early identification of persistent or growing masses- Referral for imaging and biopsy
- Understanding of surgical and post-operative care
- Monitoring for recurrence, especially in minor salivary gland cases
For students, AciCC illustrates the concept of low-grade malignancy with acinar differentiation and highlights the importance of correlating clinical and histopathological findings.
Conclusion
Acinic cell carcinoma is a rare, low-grade malignant salivary gland tumor with a good prognosis if completely excised. Awareness of its clinical presentation, histopathological features, and management principles is essential for dental and medical professionals, ensuring timely intervention and optimal long-term outcomes.