What question did this study set out to answer?

To explore the characteristics and manage secretory breast carcinoma in a young girl, emphasizing genetic insights and treatment options.

May 16, 2026Open Access

Secretory Breast Carcinoma in A Six-Year-Old Girl: Case Report With Genetic Insights and Therapeutic Implications

Puntos clave

To explore the characteristics and manage secretory breast carcinoma in a young girl, emphasizing genetic insights and treatment options.
Descriptive case report of a six-year-old girl with a breast mass, including histopathology and immunohistochemistry analysis.
Germline testing for hereditary mutations and tumor profiling for ETV6-NTRK3 fusion was conducted.
Therapeutic implications were discussed in the context of TRK inhibitors.
Histopathology showed lobular architecture and significant mitotic activity, confirming secretory breast carcinoma.
Germline testing was negative for hereditary predispositions, while tumor profiling confirmed the ETV6-NTRK3 fusion.
The patient remains disease-free six years post-surgery, indicating a successful outcome with no recurrence.

Resumen

Abstract Background Secretory breast carcinoma (SBC) is an extremely rare subtype, accounting for ~1% of breast cancers but representing the most common malignant breast tumor in pediatric patients. Although generally indolent, SBC carries a risk of local recurrence even decades after treatment. Its defining molecular hallmark is the ETV6-NTRK3 fusion. Case Presentation We describe a previously healthy six-year-old girl who presented with a 10 × 10 mm retroareolar breast mass. Histopathology revealed lobular tumor architecture with microcystic, cribriform, and tubular patterns, PAS-positive secretory material, and pronounced mitotic activity. Immunohistochemistry demonstrated positivity for S-100, MUC4, EGFR, and GATA3, with partial ER expression (20%), PR negativity, and HER2 negativity. Due to margin involvement after excisional biopsy, a simple mastectomy with sentinel lymph node biopsy was performed, followed by axillary dissection after six months for suspicious lymph nodes, which proved benign. Genetic Findings Germline testing (BRCA1/2, TP53, PTEN, CHEK2, PALB2, and others) was negative, excluding hereditary predisposition. Tumor profiling confirmed the canonical in-frame ETV6-NTRK3 fusion (ETV6 exon 5 – NTRK3 exon 13). Therapeutic Implications The presence of ETV6-NTRK3 not only confirms the diagnosis but also identifies a potential therapeutic target. TRK inhibitors (larotrectinib, entrectinib, repotrectinib) are FDA/EMA-approved for pediatric and adult solid tumors with NTRK fusions and have demonstrated high and durable response rates. Outcome Six years after surgery, the patient remains disease-free without evidence of recurrence or metastasis. Conclusion This case highlights the importance of integrating histopathology with molecular profiling in pediatric SBC. The identification of ETV6-NTRK3 provides diagnostic specificity and offers a precision oncology option in the event of relapse. Long-term surveillance and multidisciplinary follow-up remain essential for optimal care.

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