Reliability of impression cytology for the diagnosis of ocular surface squamous neoplasia employing the Biopore membrane

Aim-To evaluate the accuracy of impression cytology employing a Biopore mem brane device in the diagnosis of ocular surface squamous neoplasia (OSSN). Methods-The histology of patients undergoing excision biopsy for the suspec ted diagnosis of OSSN over a 20 month period was compared with the reported cytology of impression cytology specimens obtained preoperatively using th e Biopore membrane device. Results-25 excision biopsies were performed for suspected OSSN. There was a ccurate correlation in 20 out of the 25 cases (80%). In three cases (12%), there was poor correlation in that only a few dysplastic cells and hyperker atosis were noted on cytology, whereas histology showed keratinising dyspla sia in two cases and a moderately differentiated keratinising squamous cell carcinoma in the third. There were two cases (8%) of noncorrelation-one ke ratinising dysplasia on histology, but anucleate keratin, squamous metaplas ia, and rare atypical cells on cytology, and another case with very mild fo cal dysplasia on histology but squamous metaplasia on cytology. Review of t he cytology showed that dysplastic cells were either rare or absent from th e cytology specimens in these two cases; it was felt that these represented sampling problems rather than true false negatives. There were no false po sitives on cytology. Final diagnosis on histology was squamous cell carcino ma in one; carcinoma in situ in two; keratinising dysplasia in 15, non-kera tinising dysplasia in seven. Conclusion-Impression cytology employing the Biopore membrane accurately pr edicts the histological diagnosis of OSSN. The presence of hyperkeratosis, inflammatory cells with only a few dysplastic cells, may indicate high grad e keratinising dysplasia or squamous cell carcinoma. The method is both rap id and easy to perform in routine clinical practice. These findings suggest that there may be a role for its use in the initial assessment and follow up of patients with suspected OSSN.