“Single file” pattern in histopathology

摘要

“Singlefile”arrangement ofthetumorcells isafeature of various malignancies,and thecellsareseen arranged in linear rows which appearas if onefollowing thefootsteps ofanother.[1] Thetermhas been used interchangeablywith “Indian file” probably denotingAmerindians people's way ofwalking along atrailas illustrated in[Figure 1]a. The patternmay beappreciated both cytologically and histologically. Sometimes, this pattern isalso referred to as“cord-like” pattern ascharacterized bythe presence ofsingleline oftumorcells; this isconsidered to be highly characteristic oflobularcarcinoma ofthe breast [Figure 1]b.{Figure 1}Although, lobularcarcinomaisa distinctivefeature of breast; in head-and-neck region, this pattern hasalso been described commonly in polymorphousadenocarcinoma,and malignantepithelialtumorcharacterized by cytological uniformity, morphological diversity and an infiltrative growth pattern.[2] On case-by-casebasis, theterm“lowgrade”may beadded. Morphological diversity is seen as thetumorcells growin solid pattern,cribriformpattern, largecysticspace, orcord-like.Asaforementioned, thetumor shows infiltrative growth pattern particularly at the periphery. Thisareashows tumorcells proliferating in singlefilefashion that resembles“beads on astring”[Figure 1]c.[3] Acorresponding hand drawn picture ofsinglefile pattern in polymorphousadenocarcinomais illustrated in [Figure 1]d. It wasdemonstrated that polymorphous low-gradeadenocarcinomacontained asignificantly higher proportion ofreticular, tubularand singlefile patternsascompared tocribriformadenocarcinoma ofthesalivary gland containing a higher percentage of papillary, solid and cribriformpatterns.[4] This distinction has been omitted fromtherecent WHO Classification ofHead and Neck Tumors.[2] When cribriformpattern predominates, the distinction fromadenoid cysticcarcinoma may be difficuhowbeit, polymorphousadenocarcinomashowscytological uniformity and consistent p63+/p40? profile.