Adenoid cystic carcinoma with high-grade transformation: A report of 11 cases and a review of the literature

High-grade transformation of adenoid cystic carcinoma (ACC) (previously referred to as dedifferentiation) is a rare phenomenon that does not fit into the traditional ACC grading schemes. The importance and minimal criteria for distinction from solid (grade 111) ACC are not well established. We report I I new cases and review the literature to further define the profile of this tumor. The median age was 61 years (range: 32 to 72 y) with a male predominance (male to female ratio of 1.75: 1). The most commonly involved sites were sinonasal (4/11) and submandibular (4/11). Lymph nodes were pathologically positive in 4/7 (57.1 %) cases. Distant metastases to the lung (n = 2) and soft tissue of the shoulder (n = 1) were observed. Five of 9 patients (55.6%) died, all within 5 years with a median overall survival of 12 months. Histologically, ACC with high-grade transformation was distinguished from conventional ACC by nuclear enlargement and irregularity, higher mitotic counts, and the loss of the biphasic ductal-myoepithelial differentiation. Useful supportive criteria were prominent comedonecrosis and fibrocellular desmoplasia. The most common morphologies for the high-grade component were poorly differentiated cribriform adenocarcinoma and solid undifferentiated carcinoma. Micro-papillary and squamoid patterns were occasionally present. Ki-67 and p53 labeling indices were elevated in the high-grade components, though c-kit and cyclin-DI were not. ACC-high-grade transformation is a highly aggressive salivary gland tumor with a variety of histologic patterns. The high propensity for lymph node metastases suggests a role for neck dissection in patients with this rare tumor.