Extremely well differentiated squamous cell carcinoma of the breast. Report of a case with a comparative study of an epidermal cyst.

BACKGROUND

Although the cytologic diagnosis of malignancy by fine needle aspiration is easy in cases of moderately to poorly differentiated squamous cell carcinoma in various organs, it is not always easy in cases of the well-differentiated type.

CASE: A 46-year-old female presented with a slowly growing mass in the right breast; it was diagnosed as an extremely well differentiated squamous cell carcinoma. The diagnosis of malignancy was initially not established by fine needle aspiration cytology because of minimal cellular atypia. The smear contained many squamous cells, mainly of the superficial type, with little cellular atypia, in a background of horny material. However, neither anuclear superficial cells nor granular cells were found.

CONCLUSION

Absence of anuclear keratinized cells and granular cells is probably a helpful finding for distinguishing squamous cell carcinoma from epidermal cyst in the breast region.