Eosinophilic dysplasia of the cervix: A newly recognized variant of cervical squamous intraepithelial neoplasia

A proportion of cervical squamous intraepithelial lesions encountered in surgical pathology practice contain both metaplastic features and some degree of atypia [so-called eosinophilic dysplasia (ED)] that defy classification according to established criteria. To elucidate the nature of these lesions, we compared 44 cases of ED to 20 classic high-grade squamous intraepithelial lesions (HSILs) and 10 squamous metaplasias using a panel of biomarkers and human papillomavirus (HPV) testing. EDs were defined as 1) lack of normal maturation; 2) relatively abundant eosinophilic cytoplasm and distinct cell borders compared with conventional HSIL; 3) mildly to moderately increased nuclear to cytoplasmic ratio; and 4) focal dysplastic nuclei showing nuclear enlargement, hyperchromasia, variable nuclear membrane irregularities, and appreciable nucleoli. Expression of p16 (p16^INK4a), MIB-1 (Ki-67) labeling index, and HPV DNA detection and typing were performed on each case. The majority of EDs showed more than three atypical cells in an entire lesion but lack of apparent features of HSIL. It was common to find neighboring cervical squamous metaplasia and/or conventional SILs (either HSIL or low-grade squamous intraepithelial lesion [LSIL]). Among the 44 cases, 18 (45%) ED lesions were found to be associated with HSIL, 15 (34%) with LSIL or condylomatous lesions, and 13 (30%) EDs were seen without any SILs in the entire specimens. Area of benign squamous metaplasia was found in all ED cases. High levels of p16 and MIB-1 expression were seen in 41 (93%) of 44 ED cases with degrees of immunoreactivity closely resembling those seen with HSIL. Of 16 EDs tested, 13 (81%) were positive for HPV DNAs. Among 10 HPV-positive cases subtyped, 9 (90%) cases contained intermediate- and/or high-risk HPVs and 1 case contained a novel HPV. In the follow-up of pure ED cases, the majority showed presence of dysplastic lesions of either HSIL or LSIL on either loop electric excision procedures or Papanicolaou test samples after a 6- to 10-week period. Therefore, ED represents an unrecognized and potentially clinically significant subgroup of cervical intraepithelial lesions. Based on the unique histologic appearance of ED, its association in some cases with HSIL, the overall immunohistochemical findings, frequent association of ED with intermediate- and/or high-risk HPV infection, and limited follow-up data, we believe that ED represents a variant of HSIL (CIN 2). Since ED possesses histologic features of both dysplasia and metaplasia, we speculate that it may arise from metaplastic cervical squamous epithelium that has subsequently become infected with intermediate- or high-risk HPV.