The curious case of an inframammary accessory breast tissue fibroadenoma

A 41-year-old woman presented with an enlarging lump below the right inframammary sulcus, which caused variable pain according to menstrual cycle. On physical examination, the lump had an elastic consistency and was not fixed to the chest wall. An accessory nipple was also identified.

A standard breast study was performed, which included mammography (craniocaudal and oblique incidences) and ultrasonography. Mammography revealed breasts with scattered areas of fibroglandular densities, with no other significant features in pectoral breasts, but under the right inframammary sulcus a radiopaque circumscribed nodule was noted. Ultrasonography showed a hypoechoic homogeneous nodule, measuring 34mm parallel to the skin, with sharp contour, slightly lobulated in the upper middle portion. No calcifications nor other suspicious features were identified.

Accessory breast tissue (ABT) usually arises from an erratic resolution of the mammary ridge (or “milk line”), an ectodermal thickening that runs from the anterior axillary folds to the medial thighs through the ventral face of the body. [1] It has an estimated prevalence of 2-6% in women and 1-3% in men. [2] ABT is mostly found in axillary area, which is the most reported site (60-70% of all patients). [3] However, other locations along the “milk line” (or even in other locations, such as face and back) are also reported. [1,3]

Most patients with ABT remain asymptomatic, although the accessory tissue may respond to hormonal variations, particularly during menarche, pregnancy and lactation. It is important to have in mind that usual conditions that develop in the pectoral breast can also affect ABT. [1]

Imaging studies (such as mammography and ultrasonography) are needed not only to carry out any ABT misdiagnosis (e.g. malignancy, lymphadenopathy, vascular malformation), but also to characterise any possible breast condition that may develop in the extra pectoral breast, such as fibroadenomas. [4]

Fibroadenomas are the most frequent benign breast tumours and typically affect women between 20 and 40 years of age. On physical examination, they present as mobile masses with variable sizes that remain stable over time in 80% of cases. On ultrasonography, they usually have an oval (macrolobulated), well -ircumscribed contour and are homogeneously hypoechoic, oriented parallel to the skin. The vascularity patterns are variable, ranging from absence of colour Doppler-signal to hypervascularity. When all these criteria are found, the mass is likely benign, dismissing the need for a biopsy. Nonetheless, fibroadenomas appearances may be highly variable, sometimes with doubtful features, requiring a core biopsy for histological confirmation. [5] In this case, due to the atypical location, a core biopsy was performed and the pathology report corroborated the presumptive diagnosis. The patient underwent surgical resection three months after and is actually asymptomatic.

Written informed patient consent for publication has been obtained.