Clinically occult breast carcinoma: diagnostic approaches and role of axillary node dissection

Nonpalpable breast lesions are being detected with increasing frequency with the advent of improved mammographic techniques. Although only 20-30% of these lesions are malignant, definitive diagnosis has usually required a needle-localization excisional biopsy, which is costly and increases the psychological stress on the patient. The purpose of this retrospective study was to determine the sensitivity of ultrasound-guided fine-needle aspiration (FNA) biopsy of nonpalpable breast masses and the incidence of axillary nodal metastases in these subclinical lesions.

Seventy-one patients treated for clinically occult malignant breast tumors between 1985 and 1992 were identified. Charts were reviewed to determine the accuracy of breast ultrasonography in detecting occult mass lesions and whether ultrasound guidance improved the accuracy of FNA biopsy. In addition, the incidence of axillary lymph node involvement was noted.

Of the 71 malignant tumors, 35 were in situ and 36 were invasive. The median diameter was 0.5 cm for noninvasive lesions and 0.8 cm for invasive tumors. A mass was seen on mammography in 32 (45%) patients, microcalcifications were seen in 36 (51%), and both a mass and microcalcifications were seen in three (4%). Of the 30 patients who underwent an axillary node dissection, 4 (13%) had disease-positive nodes. Ultrasound-guided FNA was performed in 15 patients with a mass lesion, with a sensitivity of 93%.

These results indicate that ultrasound-guided FNA cytologic analysis is an accurate diagnostic technique even in small (< 1 cm), mammographically detected breast masses. In addition, the incidence of axillary nodal metastases indicates that an axillary lymph node dissection should be performed in invasive lesions, even those < 1 cm in diameter.