HSIL Is as Elusive on ThinPrep Paps as on Conventional Paps
Suzanne M Brandt, Min Guo, Michelle R Bennett, Behzad Vakil, Rana S Hoda. New York Presbyterian Hospital, Weill Cornell Medical College, New York, NY
Background: 68.6% of Conventional Pap Smears immediately preceding a histological diagnosis of HSIL (Index Pap) show “minor” abnormalities (ASC-US, AGC and LSIL) per Obstet Gynecol;1998;91:973. Corresponding data for liquid-based Pap test (ThinPrep) are scarce.
Design: All ThinPrep Pap Tests immediately preceding biopsy-proven HSIL (Index TPPT) for 4 years, 2007-2010, were evaluated. Index TPPT with “major” abnormalities (HSIL, ASC-H, LSIL-H) were considered concordant, and those with “minor” abnormalities (ASC-US, AGC, LSIL) or negative were considered discordant. Available Index TPPT were reviewed to determine causes for discrepancy.
Results: 493 patients, each with one biopsy diagnosis of HSIL (age range: 14-78 years; mean: 33; <30: 231, >30:262). 274/493 (55.5%) of Index TPPT were discordant (including 24 negative cases), and 219/493 (44.4%) were concordant (Table 1). Endocervical cells and/or transformation zone (EC/TZ) was represented in 202/219 (92.2%) concordant and 215/274 (78.4%) discordant cases (P-value<0.0001). CIN2 was histologically diagnosed in 111/219 (51%) concordant cases and 186/274 (68%) discordant cases (P value=0.0001). hr-HPV test was positive in 93% of Index TPPT (wherein tested: 365/392). 233/274 discordant index TPPT were available for review: 231/233 (99%) did not show HSIL (true-negative, TN), and 2/233 (1%) showed HSIL (false-negative, FN). Each of the two FN cases preceded histological diagnosis of HSIL by <6 weeks, and each lacked classical HSIL cytomorphology and were misinterpreted as squamous metaplasia. Main causes for discrepancy in the 231 TN Index TPPT were: clinical sampling (187/231) including 59 cases which lacked EC/TZ, excessive cytolysis (34/231) and scant squamous cellularity (10/231).