PAX8 a useful marker in adult intraocular tumour diagnosis

Paired box gene 8 (PAX8) has been shown to be a valuable diagnostic marker in certain individuals with intraocular tumours, according to a study.

“[W]e highly recommend its inclusion in diagnostic antibody panels of morphologically challenging intraocular neoplasms,” the investigators said.

This observational case series involved excision and cytologic analysis specimens of six ciliary body epithelial neoplasms, two iris epithelial neoplasms, three retinal pigment epithelial neoplasms, three intraocular medulloepitheliomas, 15 uveal melanomas, and five uveal metanocytomas.

The investigators performed hematoxylin–eosin and PAX8 immunohistochemical stains on all specimens. In appropriate cases, they also carried out bleached preparations and other immunohistochemical stains, including AE1/AE3 cytokeratin, Lin28A, and CD45.

Strong nuclear PAX8 expression was noted in the following: normal corneal epithelium, iris sphincter pupillae muscle, iris pigment epithelium and dilator muscle complex, nonpigmented and pigmented epithelia of the ciliary body, lens epithelium, and a subset of retinal neurons. The normal retinal pigment epithelium and uveal melanocytes did not stain for PAX8.

Uniform strong nuclear PAX8 immunoreactivity was observed in the ciliary body epithelial and neuroepithelial tumours (ie, adenoma, adenocarcinoma, and medulloepithelioma). All melanocytic tumours (ie, iris melanoma, ciliary–choroidal melanoma, and melanocytoma) and retinal pigment epithelial neoplasms showed negative results of PAX8, while a subset of tumour-related lymphocytes, most prominent in uveal melanoma, exhibited positive results.

The uniformity of the PAX8 staining was superior to the following: variable cytokeratin staining in the ciliary epithelial neoplasms and variable Lin28A staining in malignant medulloepithelioma. Moreover, the veracity of PAX8 staining was as similarly robust on cytologic analysis and open-flap biopsy specimens of ciliary epithelial and iris epithelial neoplasms, melanocytoma, and melanoma.