Adenoid cystic carcinoma (ACC) is an uncommon and unusually indolent cancer arising within glands and occurring mainly in the head and neck but also in the breast, trachea, lacrimal glands, skin and vulva.
ACC arising in the head and neck often has a relentless progress and poor prognosis but tumours arising in some sites (notably in the breast) may have a better prognosis. ACCs are often slow-growing but locally aggressive and particularly prone to recurrence.
- ACC accounts for about 1% of all head and neck malignancies.
- ACC of the breast is a rare subtype of breast cancer.
- The age range is unusually wide and it can occur in children. It is most common between the ages of 40 and 70 years. It occurs more often in females in a 3:2 ratio.
- The p53 tumour suppressor gene may be inactivated in advanced disease but otherwise no particular or consistent genetic or environmental factors have been identified.
- However, a recent study identifies loss of 1p32-p36 as the most frequent genetic change which was also a marker for poor prognosis in ACC of salivary glands.
It has a distinct histopathological appearance. There are three main growth patterns at histology:
- Solid. This follows a more aggressive course usually.
It may, however, be confused with basaloid squamous carcinoma.
ACC is associated with a recurrent chromosomal translocation, t(6; 9) (q22-23; p23-24), with the fusion transcript involving the genes MYB and NFIB.
Presentation depends on site, but it can present as:
- A painless slow-growing mass in the face or mouth. In one study using endoscopic resection of tumours in the paranasal sinuses and anterior skull base, ACC represented 15% of the tumours found.
- More advanced tumours may invade nerves, causing paralysis and pain. ACC is of interest to neurosurgeons and neurologists because of a tendency to infiltrate neural structures and spread perineurally. Intracranial involvement can occur but is rare.
- Tumours of the lacrimal gland may affect vision and also may cause proptosis. ACC is the most common primary malignant epithelial neoplasm affecting lacrimal glands.
- In the lung, ACC may present with respiratory symptoms. ACC is the second most common primary tumour of the trachea and carries a poor prognosis (38.5% five-year survival). Relative to squamous carcinomas it is found in younger patients and is relatively resistant to treatment.
- In the larynx it may cause voice changes and presents with hoarseness and difficulty breathing.
- ACC may present as a breast tumour and can present in men. It is a rare breast carcinoma, representing less than 1% of breast carcinomas. Generally it has a favourable prognosis.[10, 11]
- Unlike most carcinomas of the head and neck, ACC rarely spreads to regional lymph nodes. Distant metastases occurs in up to 40 % of patients. The lungs are the most common site, but liver, kidney, bones and brain are also affected by metastatic disease.
- Salivary gland tumours:
- Benign mixed salivary gland tumour.
- Mucoepidermoid carcinoma.
- Polymorphous low-grade adenocarcinoma (PLGA) shares features with ACC.
- Squamous cell carcinoma.
- Tumour (new or recurrent) may be identified by CT scan or at MRI.
- There are no serological markers, although a recent report using CD43 (a sialoglycoprotein) may be useful as an adjunct to histological examination for distinguishing ACC from PLGA and monomorphic adenoma.
- Diagnosis is by biopsy or resection followed by histological assessment.
- Investigation of immunoreactivity to identify markers has not so far proved very helpful.[3, 14]
Staging to plan treatment and assess prognosis should identify:
- Site. Some sites have a worse prognosis, often a function of the difficulty of complete surgical resection.
- Clearance of surgical margins.
- Histological subtype.
- Tumour, node and metastasis (TNM) stage.
- Aggressive surgical resection is the mainstay of treatment.
- Postoperative radiotherapy is used to try to reduce local recurrence. Some consider this should be standard therapy for ACC of the head and neck. However, there is also a suggestion from one study that it is unnecessary where surgical margins are negative.
- Neutron beam therapy may be more effective. It should be considered as initial primary treatment for locally advanced, unresectable ACC of minor salivary glands and in patients where surgery carries unacceptable morbidity.
- Chemotherapy has not produced good results. Clinical trials of combination chemotherapy are underway for metastatic and locally recurrent disease.
A wide range of complications can occur from local spread, metastasis and treatment. These are determined by site and extent of local invasion.
- ACC is a slow-growing, indolent tumour but runs a relentless course. This gives good survival figures at five years but poor figures at 15 years. The five-year survival is 89%, 10-year survival is 65% and the 15-year survival is 40%.
- Poor prognostic features include neural spread and positive surgical margins. Clinical stage, primary site and histological subtype also obviously affect prognosis.
- Although salivary gland lesions have a relatively high tendency to metastasise, ACC of the breast tends to have a much better prognosis.
- Recurrence rates are mainly influenced by tumour site, but also by clinical factors (age, sex, site and stage), postoperative treatment (radiotherapy or not) and pathological variables (grade, margins of resection and perineural invasion).
- There is a suggestion that Ki-67 markers and other markers may correlate with prognosis.[4, 15]
Further reading and references
; Adenoid cystic carcinoma of the tongue--clinicopathological study and survival Head Neck Oncol. 2009 May 291:15.
; Molecular biology of adenoid cystic carcinoma. Head Neck. 2012 Nov34(11):1665-77. doi: 10.1002/hed.21849. Epub 2011 Oct 17.
; Salivary gland adenoid cystic carcinoma: a review of chemotherapy and molecular Oral Oncol. 2006 Sep42(8):759-69. Epub 2006 Jun 6.
; Adenoid cystic carcinoma of breast: Recent advances. World J Clin Cases. 2014 Dec 162(12):732-41. doi: 10.12998/wjcc.v2.i12.732.
; Assessment of p63 expression in the salivary gland neoplasms adenoid cystic carcinoma, polymorphous low-grade adenocarcinoma, and basal cell and canalicular adenomas. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004 May
; Deletion of 1p32-p36 Is the Most Frequent Genetic Change and Poor Prognostic Marker in Adenoid Cystic Carcinoma of the Salivary Glands. Clin Cancer Res. 2008 Aug 1514(16):5181-7.
; Head and neck adenoid cystic carcinoma: what is new in biological markers and treatment? Curr Opin Otolaryngol Head Neck Surg. 2013 Apr21(2):124-9. doi: 10.1097/MOO.0b013e32835c05fd.
; High-grade adenoid cystic carcinoma originating from the lacrimal gland. Brain Tumor Pathol. 2000
; Adenoid cystic carcinoma of the trachea: a long-term problem. ANZ J Surg. 2006 Aug
; Adenoid cystic carcinoma of larynx. J Coll Physicians Surg Pak. 2006 Oct
; Adenoid cystic carcinoma of the male breast. Int Surg. 2006 Jul-Aug
; Solid variant of mammary adenoid cystic carcinoma with basaloid features: a study of nine cases. Am J Surg Pathol. 2002 Apr
; Adenoid cystic carcinoma of the breast: molecular markers, treatment, and clinical outcome. Cancer. 2002 Apr 15
; Adenoid cystic carcinoma: clinical and molecular features. Head Neck Pathol. 2013 Mar7(1):17-22. doi: 10.1007/s12105-013-0426-3. Epub 2013 Mar 5.
; Assessment of CD43 expression in adenoid cystic carcinomas, polymorphous low-grade adenocarcinomas, and monomorphic adenomas. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Oct
; Galectin-3 immunoprofile in adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma of salivary glands. Oral Oncol. 2006 Sep 21
; Management of adenoid cystic carcinoma of minor salivary glands. J Oral Maxillofac Surg. 2006 Jul
; Adenoid cystic carcinoma of the head and neck treated by surgery with or without postoperative radiation therapy: prognostic features of recurrence. Int J Radiat Oncol Biol Phys. 2006 Sep 1
; Role for postoperative radiation therapy in adenoid cystic carcinoma of the head and neck. Laryngoscope. 2004 Jul
; Long-term local control of recurrent adenoid cystic carcinoma in the parotid gland with radiotherapy and intraarterial infusion chemotherapy. Radiat Med. 2006 May
; [Prognostic analysis of adenoid cystic carcinoma of major salivary glands of 64 cases.] Ai Zheng. 2006 Sep
; Adenoid cystic carcinomas of the breast and salivary glands (or 'The strange case J Clin Pathol. 2010 Mar63(3):220-8.
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