Pitfalls in fine needle aspiration cytology of breast tumors. A report of two cases.

Two cases of fibroadenoma that were cytologically misdiagnosed as mucous carcinoma are reported. The reason for this misdiagnosis was the presence of mucus in the background of the smears. Cytologically, even if plenty of mucus is present in a smear, careful observation of the content of the mucus is necessary. A group of stromal cells in mucus or of epithelial cells dissociated from mucus suggests fibroadenoma with a mucous change in the fibromatous tissue.