Fibroadenoma in Ectopic Breast Tissue of Axilla: A Rare Entity.

Dear Editor,

A 42-year-old female presented with complaints of swelling in the left axilla since 2 months. On clinical examination, a well-defined nodular lesion measuring 1.0 cm × 1.0 cm was noted in the subcutaneous plane in the left axilla. On deep palpation, there was tenderness which developed since 3 weeks, and the nodular lesion was felt separate from the axillary tail of breast. The patient gave no positive family history for breast carcinoma. Contralateral breast/axilla did not show similar lesions. The patient was referred for ultrasonography which revealed a well-defined hypoechoic lesion measuring 12 mm × 10 mm in the left axilla with no significant internal vascularity [Figure 1a]. Differential diagnoses of lymphadenopathy/fibroadenoma were considered. Fine-needle aspiration cytology (FNAC) of the material obtained from the nodular lesion revealed clusters of epithelial cells with abundant stroma and preserved myoepithelial cells consistent with a diagnosis of fibroadenoma [Figure 1b]. A diagnosis of fibroadenoma was confirmed in the accessory breast tissue.

Figure 1

(a) Ultrasonography image demonstrating a well-circumscribed solid ovoid mass isolated from the breast with subtle posterior enhancement in the left axilla in a histopathological examination proven case of fibroadenoma in axillary ectopic breast tissue. (b) Histopathological examination image revealing well-circumscribed intracanalicular growth pattern with uniform distribution of glandular and stromal elements consistent with a diagnosis of fibroadenoma (H and E, ×4)

Embryonic milk line extends between the axilla and groin. In the course of normal development, there is resolution of most of the embryonic ridges except in the pectoral region.[1] However, the persistence of milk line in adults results in the development of supernumerary breast with a reported incidence of 0.4%–6% in females[2] and are most commonly located below the inframammary crease and axilla.[3] Pathological lesion arising from ectopic breast tissue is a very entity and hence has been presented here with focus on the differential diagnosis. On ultrasonography, ectopic breast tissue cannot be distinguished from normal breast tissue.

Masses in axilla like ectopic breast tissue may pose a diagnostic challenge and should be differentiated from lipoma, hidradenitis, follicular cyst, lymphadenopathy, fibrocystic disease, intraductal papilloma, hamartoma, or phyllodes tumor.[4] Initial mammography and ultrasonographic evaluation followed by FNAC/biopsy are indicated for suspicion of pathological lesions within the accessory breast tissue. The occurrence of fibroadenoma in accessory breast tissue is very rare and only few cases have been reported in the literature, though fibroadenoma per se is a common benign condition of the breast.[5] In conclusion, fibroadenoma arising in the ectopic breast tissue of axilla may pose to be a diagnostic dilemma and hence should be considered in the differential diagnosis along with lymphadenopathy in the setting of tender nodular lesion of the axilla.

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