What is adenoid cystic carcinoma (ACC), including its diagnosis (dc), treatment (tx), and epidemiology?

From the Guidelines

Adenoid cystic carcinoma (ACC) is a rare type of cancer that typically develops in the salivary glands but can also occur in other areas with secretory glands, and its management should prioritize complete surgical resection with wide margins, often followed by adjuvant radiation therapy to reduce local recurrence, as recommended by the ASCO guideline 1.

Diagnosis

Diagnosis of ACC involves clinical examination, imaging studies (CT, MRI), and definitive confirmation through biopsy with histopathological examination showing characteristic cribriform or "Swiss cheese" pattern with basaloid cells arranged in tubular and solid patterns.

• Clinical examination is crucial for identifying the primary tumor and assessing for any signs of local invasion or metastasis.
• Imaging studies, such as CT and MRI, help to evaluate the extent of the tumor and plan for surgical resection.
• Biopsy with histopathological examination is essential for confirming the diagnosis of ACC and determining the tumor's grade and stage.

Treatment

Treatment primarily consists of complete surgical resection with wide margins, often followed by adjuvant radiation therapy to reduce local recurrence.

• Postoperative radiation therapy should be offered to all patients with resected ACC, as it has been shown to increase locoregional control and improve overall survival 1.
• Chemotherapy has limited efficacy but may be used in metastatic disease, with targeted therapies like tyrosine kinase inhibitors being investigated.
• In the setting of ACC with limited metastases, local ablative treatments such as surgery (metastatectomy) or stereotactic body radiation therapy may be offered to delay local disease progression 1.

Epidemiology

Epidemiologically, ACC accounts for about 1% of all head and neck malignancies and 10% of all salivary gland tumors.

• It typically affects adults in their 40s to 60s with no strong gender predilection.
• The 5-year survival rate is relatively high (70-90%), but long-term prognosis is guarded due to late recurrences and distant metastases, particularly to the lungs, bone, and liver, which can occur even decades after initial treatment 1.
• Regular long-term follow-up is essential due to this persistent risk of late recurrence, with surveillance imaging or follow-up imaging for suspected or known recurrence recommended to detect and manage recurrences early 1.

From the Research

Definition and Characteristics of Adenoid Cystic Carcinoma

• Adenoid cystic carcinoma (ACC) is an uncommon tumor that usually arises in the head and neck region, mainly in the salivary glands 2.
• It is characterized by perineural invasion and demonstrates an indolent prolonged course 2, 3.
• ACC can affect both major and minor salivary glands, with a slight predilection for the latter, and commonly manifests between the 6th and 7th decades of life 3.
• The disease shows a slight female predilection, with a reported female to male ratio of 3:2 3.

Diagnosis (DC)

• Diagnosis of ACC is often challenging and frequently requires a combination of clinical examination, imaging, and histopathology 3.
• Lesions of ACC are often insidious and slow-growing, and symptoms such as pain and altered sensation are frequently associated with advanced stages of the disease 3.

Treatment (TX)

• Primary treatment of local and locoregional disease consists mainly of surgery and/or irradiation 2.
• Management of ACC is primarily surgical excision, while radiotherapy has shown to be effective in improving local control in cases with microscopic residual disease 3.
• Treatment of recurrent or metastatic tumors by radiotherapy with or without chemotherapy has so far shown limited success 3.
• Systemic therapies, including chemotherapy and targeted therapy, are being developed and studied, with some showing promise in treating ACC 4.

Epidemiology

• ACC accounts for 10% of all salivary gland malignancies, but only 1% of head and neck malignancies 3.
• The disease is not prevalent, and its etiopathogenesis is poorly understood, although several genetic patterns and biomarkers have been linked to its initiation and/or progression 3.
• Distant metastases can develop despite favorable local control, and late distant metastasis of ACC can occur after a long time interval without local recurrence 5.
• Patients who undergo primary treatment need a long-term, strict follow-up plan even if locoregional control is favorable 5.