[2] The authors of this report found a chromosome translocation in certain salivary gland tumors, i.e. a (12;15)(p13;q25) fusion gene mutation.
This mutant fusion gene also occurs in congenital fibrosarcoma, congenital mesoblastic nephroma, secretory breast cancer (also termed juvenile breast cancer), acute myelogenous leukemia, ALK-negative Inflammatory myofibroblastic tumour, and radiation-induced papillary thyroid carcinoma.
In consequence of the latter effect, the fusing protein continuously stimulates pro-growth and pro-survival pathways and thereby the malignant growth of its parent cells.
[9][11] Mammary analogue secretory carcinoma occurs somewhat more commonly in men (male to female ratio of <1.5:1.0).
[10][12] The cited histology features are insufficient to distinguish MASCSG from other Salivary gland neoplasms such as acinic cell carcinoma, low-grade cribriform cystadenocarcinoma, and adenocarcinoma not otherwise specified.
MASCSG can be distinguished from these and other histologically similar tumors by either tissue identification of a) the ETV6-NTRK3 fusion gene using Fluorescence in situ hybridization or reverse transcription polymerase chain reaction gene detection methods[13] or b) a specific pattern of marker proteins as registered using specific antibody-based detection methods, i.e. MASCSG tissue should have detectable S100 (a family of calcium binding proteins), Mammaglobin (a breast cancer marker), Keratin 7 (an intermediate filament found in epithelial cells), GATA3 (a transcription factor and breast cancer biomarker), SOX10 (a transcription factor important in neural crest origin cells and development of the peripheral nervous system), and STAT5A (a transcription factor) but lack antibody-detectable TP63 (a transcription factor in the same family as p53) and Anoctamin-1 (a voltage sensitive calcium activated chloride channel).
[9] Indeed, one patient with extensive head and neck MASCSG disease obtained an 89% fall in tumor size when treated with entrectinib.