Nonsurgical management of breast infections in nonlactating women. A word of caution. Management options for infectious mastitis have traditionally been limited to surgical drainage. With the advent of percutaneous fine needle aspiration (FNA), nonoperative treatment may be an alternative, though criteria for use have not been defined. During a 30-month period, 22 women presented with breast infection. Treatment was instituted based upon the clinical stage of infection. Patients with cellulitis (n = 8) were managed with diagnostic FNA/antibiotics. Those with focal abscess (n = 10) underwent FNA of the cavity/antibiotics. Patients with multiloculated abscess (n C = 3) underwent urgent surgical drainage. Of the 19 patients initially treated nonoperatively, resolution occurred in nine (47%); stage of infection did not effect outcome. Surgical drainage was required in the remainder; two cancers were found. FNA cytology in these (and all) patients was negative for malignancy. All underwent mammography during treatment. In 17 (77%) cancer was considered of low probability. The only patient with a mammogram highly suspicious for cancer had fat necrosis on biopsy. Bacterial cultures were positive in 79 per cent, virtually all with Gram (+) cocci. Four patients harbored Gram (-) organisms as well, two in concert with breast cancer. Conclusions: 1) select breast infections can be successfully managed nonoperatively, 2) the accuracy of FNA and mammography in the diagnosis of breast cancer may be impaired by coincident infection, 3) the finding of a Gram (-) breast infection warrants abandonment of nonoperative management in favor of tissue confirmation of the disease process. 