Abstract

Introduction: Ectopic breast tissue is due to incomplete regression and persistence of mammary ridges during development. This occurs in about 2 to 6% of the population, with accessory breast tissue mostly located in the axillary region. Accessory breast cancer is rare with incidences of around 0.2-0.6%.

Case presentation: The patient was a 49-year-old female with no comorbidity. Her mother had uterine malignancy, while two older siblings had malignancy of unsure primary origin. No other risk factors were associated. The patient had been under surveillance follow up for the past 5 years for bilateral benign breast disease. However, she had noticed left axillary swelling for the past 2 months. Clinically, there was no obvious breast lump, however presence of multiple matted left axillary lymph nodes was noted. A mammogram showed left axillary lymphadenopathy. Fine needle aspiration cytology (FNAC) showed atypical cells suggesting adenocarcinoma. Subsequently, MRI of the breast showed two large axillary lymph nodes with no abnormalities in the breasts. CT of thorax, abdomen and pelvis showed bilateral axillary lymphadenopathy. We proceeded with ultrasound-guided core biopsy which showed invasive breast carcinoma of no special type with positive oestrogen and progesterone receptors. Subsequently, the patient underwent wide local excision. Intra-operatively, we noted an accessory breast mass measuring 11 x 8 cm. Histopathology examination indicated invasive accessory breast carcinoma with clear margins. At the time of writing, we plan for left axillary clearance the following week.

Conclusion: Due to the rarity and lack of awareness of this condition among clinicians, accessory breast carcinoma is often missed and underestimated. Proper diagnosis, intervention and follow up is essential.

Additional Information

This presentation was given at the SES 2020 online conference, 4 July 2020.