AB193. SOH25_AB_246. Breast metastases from extramammary malignancies—a single tertiary centre experience

Background: Extramammary malignancies metastasizing to the breast are uncommon, comprising 0.5–6.6% of all malignant breast tumors annually. These metastases lack distinctive clinical or radiological signs, thus making it difficult to differentiate them from primary breast carcinoma or benign lesions. This poses significant diagnostic challenges, potentially resulting in a delay in initiating treatment.

Methods: A retrospective review was conducted using the breast cancer database at a tertiary university hospital. Patients who have undergone breast imaging followed by biopsy are discussed at multidisciplinary meeting (MDM). Radiological and histological findings, alongside with MDM outcomes from 2014 to 2023 were digitized. Patients with extramammary malignancies metastasizing to the breast were identified through MDM outcomes and included in the study.

Results: Fourteen patients were included in the study (12 women and 2 men; mean age: 61 years). Melanoma was the most common primary malignancy (n=6), followed by lymphoma/leukaemia (n=4) neuroendocrine tumors (n=2), ovarian adenocarcinoma (n=1), and lung adenocarcinoma (n=1). Five out of 14 patients (35.7%) presented with multifocal diseases identified on breast imaging.

Conclusions: This study demonstrated varying types of primary malignancy metastasizing to the breast. There is a lack of radiological signs to suggest extramammary breast metastases versus primary breast lesions. This further emphasizes the importance of clinical assessment and adequate tissue sampling in obtaining a diagnosis as part of the triple assessment in the breast clinic.

Keywords: Breast; histopathology; metastases; multidisciplinary meeting (MDM); imaging