What happened, in summary

A 46-year-old woman returned to the breast clinic in November 2018 because a palpable mass in her right breast had enlarged. A core biopsy of the same mass in 2016 had shown a benign fibroadenoma. New mammography and ultrasound still showed a well-circumscribed lesion, but it had increased from 0.9 cm to 1.3 cm, a 40% growth.

Because of the interval enlargement, a repeat ultrasound-guided biopsy was performed. The specimen contained fibroadenoma together with ductal carcinoma in situ and lobular carcinoma in situ. The ductal component was positive for estrogen and progesterone receptors. The lobular component was negative for E-cadherin, supporting its classification. Preoperative MRI showed a circumscribed enhancing mass with internal septations and central washout kinetics.

She underwent right lumpectomy. Final pathology again confirmed both ductal and lobular carcinoma in situ within the fibroadenoma. The surgical margins were free of tumor, with the in situ carcinoma 0.4 cm from the closest superior margin. Pathologic staging was recorded as pTis NX M not applicable. She then received adjuvant radiation therapy.

Her experience shows why a previously benign breast mass may need renewed assessment when it changes. The carcinoma was in situ rather than invasive, and treatment focused on local control with breast-conserving surgery and radiation.