A case of giant fibroadenoma of the breast (size 23x20x13 cm and weight 2680 grams) in a 43-year-old woman with short stature and gracile body build is presented. Pericanalicular fibroadenoma was detected histologically. One year after mastectomy the patient is in good health, with no recurrences. The case is discussed in the light of the diagnostic difficulties, which lead to radical mastectomy. Giant fibroadenomas have to be differentiated from phylloid cystosarcoma by the lack of leaf-like structures and stromal cell atypia and from the breast hamartoma and asymmetric breast hypertrophy in girls by the lack of mammary lobules. Giant fibroadenoma should take its due place in the diagnostic algorithm of the breast tumors.