Primary ectopic breast carcinoma in a supernumerary breast arising in the anterior chest wall: a case report and review of the literature
A 48-year-old female presented with a 6-week history of a tender mass inferior to the right inframammary fold following trauma.\nAntibiotics were initiated for presumed infection; however, the mass persisted, prompting surgical referral. Clinical examination demonstrated a 2 × 1 cm superficial mass, with adjacent accessory nipple. An ultrasound confirmed a 15-mm hypo-echoic mass consistent with a sebaceous cyst; however, a core biopsy confirmed a Grade 2 invasive ductal carcinoma (IDC), strongly positive for oestrogen and progesterone receptors (Allred scores of ER 7, PR7). Immunohistochemistry for Her 2 status was negative (0).\nMagnetic resonance imaging (MRI) confirmed a 22 × 12 mm spiculated (Fig. ) mass inferior to the right inframammary fold deep to the accessory nipple, compatible with a supernumerary breast. There was evidence of overlying skin infiltration, with a clear margin of normal tissue between the tumour and costal fascia. No masses were noted in either breast.\nShe proceeded to a wide local excision of the entire accessory breast, nipple-areolar complex and an additional ellipse of skin. Sentinel node biopsy was negative, with no further axillary dissection performed.\nHistopathology revealed a Grade 2, 19-mm IDC. There was no lymphovascular invasion and radial margins were clear by >10 mm. The deep margin was 2 mm, but the anterior subcutaneous margin was 0 mm. In view of the positive anterior margin the patient proceeded to adjuvant radiotherapy.\nThe patient underwent a CT planning scan to assess the depth of tissue to be treated. A 10 × 7 cm rectangular electron field was applied to the tumour bed incorporating the excision scar. The patient was then treated with 9 megavoltage (MEV) electrons to a dose of 40 Gy in 15 fractions, over 21 days receiving 2.67 Gy per fraction. The Dmax treatment depth was 12 mm, with the 90% isodose at 18 mm. The ipsilateral breast was not included in the treatment field as the tumour was in a separate accessory breast which had been fully excised. The patient subsequently commenced Tamoxifen. Twelve weeks post-radiotherapy, she was in remission and all acute radiotherapy reaction had subsided.