DIAGNOSTIC-SIGNIFICANCE OF SIGNET-RING CELLS IN FINE-NEEDLE ASPIRATESOF THE BREAST

Fine-needle aspiration (FNA) is a reliable and cost-effective procedur e in the evaluation and management of breast lesions. One diagnostic d ilemma that may sometimes arise is the finding of signer ring cells. T he isolated finding of such cells in aspirate smears may be particular ly problematic in cases of low cellularity or those with otherwise ben ign features. Although it is generally held that such cells ave almost exclusively associated with carcinoma (particularly the lobular subty pe), their significance in FNA smears has never been systematically ev aluated. To establish their diagnostic utility, we evaluated aspirate smears from 150 cases of histologically proven benign (77) and maligna nt (73) breast lesions for the presence of signet ring cells, defined as those containing a prominent intracytoplasmic vacuole with nuclear. displacement. Signet ring cells were identified in 71% of malignant c ases (75% of ductal carcinomas and 71% of lobular carcinomas), mostly as single cells or within small, loosely cohesive tissue fragments. Su ch cells were also present in 6% of histologically proven benign lesio ns, most commonly within large tissue fragments. Many of these cells w ere proven to be vacuolated myoepithe lial cells, based on histologic correlation and immunostaining results using anti-muscle-specific acti n. On the basis of these findings, we conclude that (1) the presence o f signet ring cells within small loose tissue fragments or as single c ells in FNA smears should prompt close clinical follow-up (including r epeat FNA and perhaps surgical biopsy), regardless of smear cellularit y, (2) the presence of signet ring cells in cases of adenocarcinoma do es not pr-edict a particular tumor subtype, and (3) rare benign breast lesions may contain signet ring cells, particularly within lar-ge tis sue fragments, and do not, in isolation, warrant surgical biopsy to ex clude malignancy. (C) 1997 Wiley-Liss, Inc.