Determining tumor category of ocular surface squamous neoplasia: science or art?

Diagnosis and staging of ocular surface squamous neoplasia

Background: Ocular surface squamous neoplasia (OSSN) is the most common ocular tumour. The diagnosis of OSSN is based on clinical suspicion and confirmed by various diagnostic modalities, of which histology is the gold standard. With the move to less invasive management options such as topical chemo- or immunotherapy, less invasive diagnostic options have come to the fore.Aim: The purpose of this article was to review the current staging and diagnostic modalities for OSSN with a focus on less invasive modalities.Method: A literature review was performed for publications on ocular surface neoplasia and diagnostic modalities.Results: Histology is the gold standard for diagnosing OSSN. Cytology has been shown to be a simple, repeatable and minimally invasive diagnostic modality, which also allows for additional testing such as polymerase chain reaction. Anterior segment optical coherence tomography provides a non-contact method of evaluating the ocular surface, with OSSN showing a thickened hyper-reflective epithelium, abrupt transition zone and demarcation line. Vital dyes are used less commonly with high sensitivity, but lower specificity for OSSN. Finally, confocal microscopy provides en-face images of the ocular surface, with OSSN showing a classic ‘starry night’ appearance.Conclusion: Histology remains the gold standard for diagnosis; however, with the increasing use of topical therapy for OSSN, there has been an increase in the uptake of less invasive diagnostic modalities.

Ocular surface squamous neoplasia: Population demographics, pathogenesis and risk factors

Background: Ocular surface squamous neoplasia (OSSN) is a unifying term used to describe conjunctival intra-epithelial neoplasia, squamous cell carcinoma in situ and invasive squamous cell carcinoma.Aim: The aim of this article was to describe the demographics, clinical features, pathogenesis and risk factors of OSSN.Method: A literature search was conducted using the search criteria ‘ocular surface squamous neoplasia’, ‘diagnosis’, ‘epidemiology’, ‘pathogenesis’ and ‘risk factors’.Results: Ocular surface squamous neoplasia is the most common ocular tumour, with incidence rates ranging from 0.01 to 3.4 per 100 000 persons/year. There are two main patterns  of disease presentation: older white males in temperate climates where human immunodeficiency virus (HIV) and human papilloma virus (HPV) are not associated; and a younger patient population in tropical climates where HIV and HPV are more prevalent. The pathogenesis primarily revolves around ultraviolet B exposure and HPV infection that cause genetic mutations and uncontrolled cellular proliferation, whilst HIV infection and vitamin A impair tumour surveillance mechanisms. Ocular surface squamous neoplasia is first suspected clinically before formal confirmation of the diagnosis. Morphologically, it can be divided into three groups: placoid, nodular and diffuse. Placoid lesions can further be sub-divided into gelatinous, leukoplakic and papilliform lesions. Nodular lesions have the poorest prognosis, with the highest risk of metastasis and recurrence.Conclusion: Ocular surface squamous neoplasia is a common ocular tumour associated with ultraviolet radiation, HPV and HIV infection. The pathogenesis revolves around acquired genetic mutations, unregulated cellular proliferation and impaired tumour surveillance mechanisms.