Mammary Analog Secretory Carcinoma (MASC)
Mammary analog secretory carcinoma (also known as MASC) is a form of salivary gland cancer most commonly starting in the parotid gland. Only recently discovered, MASC is similar in many ways to secretory breast cancer, and prior to its discovery many MASC cancers may have been misclassified as other cancer types. People living with MASC may be eligible candidates for enrollment in the STARTRK-2 trial.
In 2010, researchers discovered that most MASC tumors were caused by rearrangements in the NTRK3 gene.6 This means that MASC tumors may respond well to entrectinib, a new investigational therapy targeting NTRK, ALK, and ROS1 fusions, and the subject of the STARTRK-2 clinical trial. (For information on other types of salivary gland cancer, please visit our salivary gland cancer page.)
Because MASC is similar to other types of tumors, it may be misdiagnosed. A simple diagnostic test can be performed to see if someone with salivary gland cancer has MASC.7 For example, a study conducted in Japan found that 10 of 18 patients diagnosed with acinic cell carcinoma actually had MASC.8 Similarly, in a second study performed in Taiwan, 6 of 21 cases of children originally diagnosed with acinic cell carcinoma between 2000 and 2011 were later reclassified as having MASC.9
MASC, NTRK Fusions, and Entrectinib
In a Phase 1 study of entrectinib, a 34-year-old woman with MASC at Memorial Sloan Kettering Cancer Center in New York City was initially described as having acinic cell carcinoma. Her disease continued to progress even after several other approaches to treatment, including chemotherapy and the drug crizotinib. After molecular profiling of her tumor, it was identified to harbor an ETV6-NTRK3 fusion, and her diagnosis was changed to MASC. After receiving entrectinib she experienced an 89% reduction in tumor size.10 Spark a discussion with your healthcare provider to see if NTRK testing may be a beneficial addition to your care plan.
See if you or a loved one may be eligible for the study.
6 Skálová A, Vanecek T, Sima R, Laco J, Weinreb I, Perez-Ordonez B, Starek I, Geierova M, Simpson RH, Passador-Santos F, Ryska A, Leivo I, Kinkor Z, Michal M. Mammary analogue secretory carcinoma of salivary glands, containing the ETV6-NTRK3 fusion gene: a hitherto undescribed salivary gland tumor entity. Am J Surg Pathol. 2010 May; 34(5):599-608. doi: 10.1097/PAS.0b013e3181d9efcc. PubMed PMID: 20410810.
7 Bishop J, Yonescu R, Batista D, et al. Most Nonparotid Acinic Cell Carcinomas Represent Mammary Analog Secretory Carcinomas. Am J Surg Pathol. 2013;37:1053–1057.
8 Makoto Urano M, Nagao T Kuroda M et al. Human Pathology (2015) 46, 94–103
9 Hsieh M, Chou Y, Yeh, S, Chang Y. Virchows Arch (2015) 467:145–153
10 Drilon A, Li G, Drogan S, et al. What hides behind the MASC: clinical response and acquired resistance to entrectinib after ETV6-NTRK3 identification in a mammary analogue secretory carcinoma (MASC) [published online February 15, 2016]. Annals of Oncology.