Adenoid cystic carcinoma of minor salivary glands and rare sites

Objectives: Adenoid cystic carcinomas (ACCs) are rare malignant tumours of salivary glands. Their occurrence at numerous other body sites is rare and poorly described. Frequent local recurrences, late distant metastasis and perineural invasion are commonly seen in these tumours. The aim of this study was to analyse the array of these tumours at various body sites. Materials and Methods: A single centre retrospective search over two years revealed 18 cases whose clinical, epidemiological, histomorphological and immunohistochemical findings were evaluated. Results: Tumour sites in decreasing order of frequency were minor salivary glands of the oral cavity, nasal cavity, maxillary sinus, larynx, bronchus and one each from the breast and cervix. The mean age of presentation was 50 years and it was more frequently seen in females. The most common histological patterns were tubular and cribriform. Solid pattern was seenpredominantly in ACCsof floor of mouth, maxillary sinus and upper gingivobuccal sulcus (GBS). Perineural invasion was seenin tumours ofminor salivary glands of oral cavity and maxillary sinus.Local invasion was seen in ACC oforal cavity, maxillary sinus and larynx. Conclusion: Although ACCsoccur most frequently in the major salivary glands, more than one third of cases occur in minor salivary glands in the head and neck and lower respiratory tract, and other sites more rarely. These have a characteristic histomorphology pattern which can be identified easily. Immunohistochemistry plays a limited role in diagnosis on small biopsy specimens. Radical surgical excision with or without post-operative radiation therapy is the treatment of choice.