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4 slides generated from the cancer page, with a quiz from the open benchmark and speaker notes that cite the sources. Arrow keys move between slides; Print gives one slide per page.
Secretory carcinoma is a very rare, slow-growing breast cancer first described in children, whose cells make milk-like secretions. It is usually triple-negative but almost always carries the ETV6-NTRK3 gene fusion, so the rare patient whose tumour spreads can be treated with an NTRK inhibitor tablet, and most need no chemotherapy.
Secretory breast carcinoma is a rare subtype of infiltrating ductal-origin carcinoma that expresses the ETV6-NTRK3 gene fusion, first cloned in paediatric mesenchymal cancers; the fusion was confirmed in 12 of 13 cases (92 percent) but in no other ductal carcinomas, and its expression transformed mammary epithelial cells into gland-forming tumours in mice, establishing it as a primary oncogenic event (Tognon 2002). Histologically the tumour shows microcystic, solid and tubular patterns with abundant intracellular and extracellular secretion, is usually low grade and often triple-negative or weakly ER-positive with a basal-like immunophenotype (Cserni 2021; Thomas 2023). The European Working Group for Breast Screening Pathology places secretory carcinoma among the triple-negative special types with an indolent course whose patients are unlikely to benefit from systemic chemotherapy, favouring surgery with or without radiotherapy (Cserni 2021). Because the ETV6-NTRK3 fusion is an NTRK fusion, the tumour-agnostic approvals of larotrectinib and entrectinib apply to the rare metastatic case.
| Setting | Approach | Guideline |
|---|---|---|
| Localised disease | Surgery with clear margins, radiotherapy after breast conservation; chemotherapy is usually not indicated for this indolent type (European working group consensus). | not mapped |
| Metastatic disease (rare) | NTRK inhibitors (larotrectinib, entrectinib) under their tumour-agnostic approvals for NTRK fusion-positive solid tumours. | not mapped |