2021 年 48 巻 5 号 p. 293-297
Ectopic breast tissue is a common anomaly of the breast that generally presents along the embryonic milk line; however, fibroadenoma of ectopic breast tissue is a rare disease. In this article, we report a rare case of fibroadenoma that developed in the ectopic breast tissue of the right axilla in a 25-year-old Japanese woman. Ultrasonography, fine-needle aspiration cytology (FNAC), and core needle biopsy (CNB) were done, and the mass was diagnosed as fibroadenoma of the ectopic breast tissue. As with normal breast tissue, various breast tumors can develop in ectopic breast tissue. In addition to ectopic breast tumors, axillary tumors need to be further differentiated from metastatic lymph nodes, abscesses, lymphomas, and so forth; thus, it is difficult to diagnose such tumors quickly and accurately. Ultrasonography, cytology, and histology are invaluable for determining the diagnosis and treatment.
