AB164. SOH21AS161. Ductal carcinoma in situ in fibroepithelial breast lesions, can it be diagnosed preoperatively?—Review of literature and case report

Background: Ductal carcinoma in situ (DCIS) rarely forms from within a phyllodes tumour. It is crucial to identify the presence of DCIS in these lesions preoperatively as surgery would involve clear margins as opposed to simple lumpectomies for benign phyllodes tumours. We aimed to review published literature and report a case.

Methods: A case of DCIS in a benign phyllodes tumour identified in postoperative histology in a 45-year-old is reported. All published literature in PubMed/Medline, Ovid and Cochrane library were reviewed.

Results: A 45-year-old female presented with a smooth, benign-feeling lump. Triple assessment confirmed an 8 cm breast imaging reporting and data system (BiRADS) 3 lesion, which was fibroadenoma with no cytological atypia on core biopsy. Following multidisciplinary meeting (MDM) discussion, she underwent a lumpectomy. Postoperative histology confirmed benign phyllodes with low-grade DCIS, no invasive focus. She chose to have mastectomy and immediate deep inferior epigastric perforator reconstruction. Database search identified 32 cases of DCIS within phyllodes, aged 19 to 80 years old. No higher-level evidence was found. 39% of lesions occurred in malignant phyllodes. The rest occurred in borderline or benign tumours. Tumour size ranged from 2 to 21 cm. Three of the published 32 cases (9.4%) were diagnosed preoperatively as DCIS within a fibroepithelial stroma on core biopsy.

Conclusions: There were no clinical or radiological signs that consistently identified the presence of DCIS within fibroepithelial tumours. We observed in the literature that preoperative pathology identified DCIS in phyllodes tumours that were smaller than 5 cm. This might suggest increased false negative biopsy rate in lesions bigger than 5 cm.

Keywords: Breast cancer; breast surgery; ductal carcinoma in situ (DCIS); fibroepithelial lesion; phyllodes tumour