Mammary Analogue Secretory Carcinoma (MASC)

Overview

Mammary Analogue Secretory Carcinoma is a rare salivary gland carcinoma defined by the ETV6-NTRK3 fusion, which is also found in secretory carcinoma of the breast. Note: the OncoTree code MASC officially maps to “Metaplastic Adenosquamous Carcinoma” under Breast Cancer; within the corpus and the MSK head and neck dataset hnc_mskcc_2016, MASC is used specifically for salivary-gland Mammary Analogue Secretory Carcinoma. This entity is historically misclassified as Acinic Cell Carcinoma due to histologic overlap; molecular diagnosis via NTRK3 fusion is definitive.

Cohorts in the corpus

• hnc_mskcc_2016 — 2 cases reclassified from acinic cell carcinoma to MASC by detection of ETV6-NTRK3 fusion on MSK-IMPACT 410-gene panel PMID:27442865.

Recurrent alterations

• ETV6-NTRK3 fusion — defining molecular event; identified in 2 tumors originally diagnosed as acinic cell carcinoma; both showed major or near-complete responses to TRK inhibitor therapy PMID:27442865.

Subtypes

• MASC is defined by ETV6-NTRK3 fusion; other NTRK3 fusions may occur in this entity. All tumors histologically classified as acinic cell carcinoma should be evaluated for this fusion PMID:27442865.

Therapeutic landscape

• TRK inhibitors — both reclassified MASC patients in the MSK-IMPACT cohort enrolled on a TRK inhibitor basket trial with major or near-complete responses; this represents a successful application of NGS-driven diagnosis reclassification to enable targeted therapy PMID:27442865.

Sources

• PMID:27442865 — Morris et al. 2017 (JAMA Oncol). ETV6-NTRK3 fusion identified by MSK-IMPACT in 2 salivary tumors initially diagnosed as acinic cell carcinoma, reclassifying them as MASC with dramatic TRK inhibitor responses.

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