Introduction: Supernumerary breast or polymastia is a well-documented anomaly of the breast, and commonly presents along the embryonic milk line extending between the axilla and groin. However, cases of polymastia have been recorded in the face, vulva and perineum. The clinical significances of these anomalies include their susceptibility to inflammatory and malignant changes, and their association with other congenital anomalies of the urinary and cardiovascular systems.
Case report: The present article reports a case of fibroadenoma developing in the supernumerary breast of the right axilla in a 17 year old girl. It is uncommon to find such palpable masses in young patients Clinical and sonographic examination of both breasts revealed no abnormalities and no lymph nodes were detected in the axillae or the neck. No associated urologic or cardiovascular abnormalities were found, and the histopathological examination of the excisional biopsy samples showed a well-defined, capsulated intracanalicular type of fibroadenoma similar to that of eutopic mammary tissue.
Discussion: We have described a rare case of fibroadenoma in an accessory breast in a young woman. There are a fewer than 40 reports in world about this subject of which differential diagnose include cancer in axillary supernumerary breast, hidradenitis, axillary lymphadenomegaly, lipomas, anexial cutaneous neoplasia, cysts and phylloid tumor. The combination of clinical examination, ultrasound and cytology leads to adequate treatment, especially surgical one. The investigation could be confused owing to the suspicious findings from cytology. In this case, in the fact of the findings and differential diagnosis, the histopathological study has concluded the diagnosis. Despite of its high sensitivity, the cytology has a low specificity and could create positive false. On the other hand, atypical lesions can be seen in fibroadenomas, especially in younger patients, pregnant one and hormonal contraception use. Although there are a few reports, our case report is similar to current medical registers and, after surgical treatment, it possesses an excellent prognoses.