Squamous Intraepithelial Lesion of Intermediate Grade: Cytologic-Histologic Correlation and Comparison of Positive Predictive Values
Pamela Tauchi-Nishi, Christopher Gima, Nila Win, Jeanae Kaneshiro, Thomas Namiki, Mark Hiraoka. University of Hawaii/Hawaii Pathologists Laboratory, Honolulu, HI; University of Hawaii, Honolulu, HI
Background: Within the 2001 Bethesda Reporting System (TBS) for Cervical Cytology, Squamous Intraepithelial Lesion of Intermediate Grade (SIL-NOS) is a diagnostic category that is only briefly defined. Despite this, the recent literature is replete with articles about SIL-NOS, with reported positive predictive values (PPV) for CIN 2+ ranging from 23-65%. We present our data regarding SIL-NOS, and compare its histologic correlation with those of other Pap test diagnoses.
Design: Between 2002-2011, 1,026,470 Pap tests were examined, including 67% SurePath, 32% conventional, and 1% ThinPrep preparations. Subsequent correlating biopsies were categorized as either negative, CIN 1 (low grade dysplasia/condyloma), and CIN 2+ (high grade dysplasia/cancer). As defined in TBS, a diagnosis of SIL-NOS was rendered in the presence of atypical squamous metaplastic cells or keratinized dysplastic cells, that raised the possibility of, but were not diagnostic for HSIL. Other diagnostic criteria included the predominance of LSIL cells with only rare higher grade cells. The Chi-Square test was employed for statistical analysis.
Results: 43,862 cases (4.3%) were flagged as abnormal, including 1.5% ASCUS, 0.1% ASC-H, 1.8% LSIL, and 0.2% HSIL results. SIL NOS was diagnosed in 2,475 (0.2%) cases. 23,243 correlating biopsies were examined (Table 1). The PPV for CIN 2+ for SIL-NOS (42%) was intermediate between that of LSIL (12%) and HSIL (69%), and differed significantly (P<0.01). The patients' ages and duration from Pap smear to biopsy did not vary between the diagnostic categories. No statistically significant differences were noted in SIL-NOS PPVs between conventional and SurePath methods (P=0.11) and amongst pathologists (P=0.97). Furthermore, these PPV values showed no significant variation over the 10 year period (P=0.27).
Conclusions: SIL-NOS is a distinct diagnostic entity from LSIL and HSIL, which is reproducible between pathologists and over time. Further study of SIL-NOS including examination of clinical relevance, and more detailed characterization within TBS, is warranted.
|Cytologic Diagnosis||No. Cases||Histologic Diagnosis|
|Negative||CIN 1||CIN 2+|
|ASC-US||6032||3603 (60%)||1337 (22%)||1092 (18%)|
|ASC-H||974||425 (44%)||87 (9%)||462 (47%)|
|LSIL||12353||6817 (55%)||4104 (33%)||1432 (12%)|
|HSIL||1907||504 (26%)||92 (5%)||1311 (69%)|
|SIL-NOS||1977||757 (38%)||387 (20%)||833 (42%)|
|Total||23243||12106 (52%)||6007 (26%)||5130 (22%)|