Abnormal cytokeratin expression in low‐grade conjunctival intraepithelial neoplasia

A 67-year-old man was referred to Yamaguchi University Hospital with a complaint of visual disturbance in the right eye. His best-corrected visual acuity was 6/15 OD. We observed a white-grey frosted lesion on the right cornea extending from the temporal limbus and without neoplastic pannus (Fig. 1a). Fluorescein staining revealed that the corneal lesion was sharply marginated by dense superficial punctate keratopathy. Rose-bengal staining was also positive for the lesion and revealed that it extended to the temporal conjunctiva. We diagnosed the patient with a corneal-conjunctival tumour of the right eye and performed en bloc simple tumour resection. His best-corrected visual acuity of the right eye recovered to 6/6 within 7 days after surgery, and no recurrence of the tumour was apparent up to 1 year after surgery. We subjected the surgical specimen to pathological analysis. Haematoxylin–eosin staining revealed that epithelial cells of the cornea and the conjunctiva were present in 8 to 10 layers (Fig. 1b). Nuclei of the tumour cells were mildly to moderately misshapen in the basal cell layer (Fig. 1c). Intracellular vacuoles were also observed in the tumour cells. The cells in the surface layer of the tumour manifested keratinization with epithelial differentiation. On the basis of the clinical appearance and pathological findings, we diagnosed the lesion as mild stage of conjunctival intraepithelial neoplasia (CIN). To investigate the characteristics of keratin expression in CIN, we further subjected the surgical specimen to immunostaining for the corneal epithelial cell-specific keratin 12, the conjunctival epithelial cell-specific keratin 4 and the basal epithelial cell-specific keratin 14 (Fig. 2), respectively. The conjunctival portion of the lesion manifested vacuolation and, with the exception of basal cells, was positive for keratin 12 staining. Keratin 14 was detected in the basal cells of this region, whereas keratin 4 showed a low level of staining in the superficial cells. In the corneal region of the lesion, the epithelial cells again manifested the accumulation of vacuoles and other cellular components. Immunostaining for keratin 12 revealed uneven expression in the epithelium of the corneal lesion, with cells in the basal region not expressing this keratin. The pattern of keratin 4 staining in the corneal lesion overlapped with that of keratin 12, especially in the vacuolated region. Keratin 14 was also expressed in regions of the corneal lesion positive for keratins 12 and 4, but its expression pattern was not uniform. It was detected in all layers of the epithelium at the limbal side but was not present in the basal cells at the other side of the tumour. Keratins 12 and 14 are specifically expressed in all corneal epithelial cells and all basal epithelial cells at the normal ocular surface, respectively. Keratin 4 is expressed in conjunctival epithelial cells as well as keratin 3. In the corneal lesion of the patient, the expression pattern of keratin 12 was not uniform, and keratin 14 was not expressed throughout the basal cell layer. The expression of cytokeratins in the conjunctival portion of the lesion also differed from that in the normal conjunctiva, with keratin 12 being detected in all layers except the basal cell layer and keratin 4 being present only in the superficial cell layer. This ectopic expression of keratin 12 in the conjunctival lesion also indicated that, like the corneal lesion, the differentiation level of conjunctiva lesion was altered. Our observations with this patient thus suggest Figure 1. Slit-lamp photographs of the right eye of the patient. (a) A white-grey frosted lesion extending from the limbus into the cornea was observed. (b) Low-magnification image of the specimen. (c) High-magnification image of epithelial cells of the tumour. Clinical and Experimental Ophthalmology 2010; 38: 899–902 doi: 10.1111/j.1442-9071.2010. 02351.x