Adenoid cystic carcinoma: clinical and molecular features

Abstract

The clinical features and common molecular alterations of adenoid cystic carcinoma (ACC) are reviewed in this paper. ACC is an uncommon neoplasm that most frequently arises in salivary glands and related tissue in the head and neck region. ACC has distinct histologic features, with cribriform and tubular growth patterns of basaloid cells displaying a predominantly myoepithelial cellular phenotype. This neoplasm also has uncommon clinical features of rare regional lymph node metastasis and a prolonged but relentlessly progressive clinical course. Clinical outcome in ACC is correlated to histologic grade, which is correlated to the degree of aneuploidy and genetic alterations present in the tumor genomes. Recent studies have identified that the majority of ACC contain alterations of the MYB gene, usually resulting in a fusion gene product with the NFIB gene by a t(6;9) translocation event. The molecular consequences of this alteration are incompletely understood, as are secondary molecular alterations that contribute to the neoplastic phenotype of ACC.

Fig. 1

Histologic types and grades of ACC. a Cribriform pattern, with no solid growth component (Grade 1). b Tubular pattern, with no solid component (Grade 1). c Cribriform growth pattern, with areas of solid growth comprising less than 30 % of tumor (Grade 2). d Predominantly solid growth pattern (Grade 3). All figures H&E stain, original magnification ×40

Fig. 2

Examples of MYB alterations in ACC. a Immunohistochemical stain for MYB showing strong diffuse nuclear staining. Original magnification ×100. b Break-apart FISH analysis for MYB with 5′ green probe and 3′ red probe. The ACC tumor cell reveals one wild type MYB gene locus (yellow signal) and evidence of break-apart of the second MYB gene locus, with separate red and green signals. Original magnification ×1500