A Case of Estrogen Receptor Positive Secretory Carcinoma in a 9-Year-old Girl With ETV6-NTRK3 Fusion Gene

Abstract

The patient was a 9-year-old premenarcheal pediatric female, whose chief complaint was a well-circumscribed palpable right breast mass without nipple discharge. Although the patient had noticed the lump 2 years prior to hospital admission, its size (1.5 × 1.3 cm) had been stable. There was no family history or previous history of malignancies. Physical examination showed a well-delimited, elastic-firm and movable tumor just beneath the nipple and areolar complex. Regional lymph nodes were not palpable. Ultrasonography and breast computed tomography revealed a subareolar oval-shaped tumor exhibiting homogeneous echogenicity with clear margins. Distant metastases could not be detected using whole-body computed tomographic scans. A fine-needle aspiration cytology specimen showed atypical cells with prominent nucleoli and abundant intracellular secretory material, suggesting the possibility of secretory carcinoma. Histopathological analysis of the core needle biopsy specimen revealed that the tumor was a secretory carcinoma. The patient underwent total mastectomy with sentinel lymph node biopsy. Metastases were not observed in the removed lymph nodes. Estrogen receptor was weakly positive and progesterone receptor was negative. Human epidermal growth factor receptor 2 expression was also negative. In addition, the ETV6 (exon 5) and NTRK3 (exon 13) fusion gene was detected using the reverse transcription-polymerase chain reaction method. This gene is considered specific for secretory carcinoma. Immunohistochemistry revealed weak basal differentiation [cytokeratin 5/6(CK5/6)(+), vimentin(+) and epidermal growth factor receptor(+)]. The patient has received no adjuvant therapy and is currently disease free at 12 months after surgery.