AB156. SOH22ABS143. High-grade ductal carcinoma in situ (DCIS) arising within fibroadenoma in a teenager: a rare case report and review of the literature

Background: Breast cancer arising within fibroadenoma (BcaFad) is extremely rare synchronous pathology, occurring in 0.002% to 0.125% fibroadenoma (FA) specimens. BcaFad typically is identified in women within the fifth and sixth decade with ductal carcinoma in situ (DCIS) being found more common than invasive carcinoma. Symptomatic, progressively enlarging masses typically leads to surgical excision however the optimal management of patients with BcaFad is still not clear.

Case Description: We report the case of an 18-year-old female who presented to our institute triple assessment breast clinic complaining of a right breast lump. A 2.9-centimetre right lower inner quadrant lump was identified on ultrasonography, and subsequent core biopsy revealed high-grade DCIS within a FA. Bilateral breast magnetic resonance imaging (MRI) revealed no additional masses. Surgical histopathology revealed intermediate to high-grade DCIS with luminal necrosis, the largest focus being 5 millimetres and immunohistochemistry evaluation of ER status was positive. Postoperative adjuvant whole breast (50 Gy) and tumour bed boost radiation therapy was preformed and adjuvant endocrine therapy, tamoxifen, was initiated for 5 years. Surveillance will include annual exam and bilateral breast MRI.

Conclusions: Our case represents only the second reported occurrence of BcaFad in a teenage patient challenging the accepted risk evaluations of benign breast lumps in young women. Thorough assessment and decisive action led to a satisfactory outcome. Clinicians are encouraged to keep such events in their differential diagnosis. If not diagnosed promptly BcaFad may result in significant poor outcomes.

Keywords: Adolescent; breast cancer arising within fibroadenoma (BcaFad); ductal carcinoma in situ (DCIS); fibroadenoma (FA); rare