Is a diagnosis of infiltrating versus in situ ductal carcinoma of the breast possible in fine-needle aspiration specimens?

BACKGROUND. With widespread use of mammographic screening, more cases of ductal carcinoma in situ (DCIS) are being detected. Fine-needle aspiration (FNA) is an established and reliable method for diagnosing breast carcinoma. However, its usefulness in distinguishing infiltrating ductal carcinoma (IDC) from DCIS is controversial. METHODS, The authors retrospectively reviewed 36 breast FNAs (23 palpable lesions and 13 nonpalpable lesions) that were confirmed histologically as being exclusively DCIS. On review, 27 cases (75%) were categorized as carcinomas, and 9 cases (25%) were categorized as proliferative lesions with atypia. Findings of only these 27 carcinomas were compared with findings of 42 breast FNAs that surgically were proven to be IDC (greater than or equal to 85% invasive). Five key cytologic features compared included the presence of fibroadipose tissue, stromal fragments, benign epithelial groups, angulated tumor cell clusters, and tubular structures of tumor cells; for the first three features, the proximity with tumor cells also was noted. RESULTS. The presence of stromal fragments associated with tumor cells was significantly different between cases of DCIS (9 of 27; 33%) and IDC (29 of 42; 69%) (P = 0.006). Tubular structures were present only in IDCs (10 of 42; 24%) (P = 0.02). Nine of ten IDCs that had tubular structures also contained stromal fragments. No other cytologic features were different statistically between IDC and DCIS on FNA specimens. CONCLUSIONS. Tubular structures of tumor cells and the presence of stromal fragments in breast FNA are significant indicators of stromal invasion. However, the low occurrence rate of tubular structures (24% in this series) in IDC and the low specificity of stromal fragments limit their utility in separating IDC from DCIS. Nonetheless, if present, tubular structures in conjunction with stromal fragments can be used to evaluate stromal invasion in patients whose disease is being managed surgically. (C) 1998 American Cancer Society.