BACKGROUND

Numerous studies have reported considerable heterogeneity in breast ductal carcinoma with microinvasion (DCIS-MI) regarding clinical presentation, progression potential, and treatment strategies.

CASE PRESENTATION

In this work, we report a case of rapidly progressing multiple metastases in a patient with DCIS-MI following conventional treatment. Subsequent fluorescence hybridization (FISH) testing revealed HER2 gene overexpression. After receiving 10 cycles of trastuzumab-targeted therapy, the patient achieved a favorable prognosis and remains stable to date.

CONCLUSION

This case suggests that even patients with microinvasive lesions who are HER2-positive may exhibit unexpected stability under targeted therapy, warranting close surveillance in such cases.