Seborrheic keratosis of conjunctiva simulating a malignant melanoma - An immunocytochemical study with impression cytology

Objectives Seborrheic keratosis on the conjunctiva appears to have never be en reported in the literature. The authors report here a well-documented ca se of seborrheic keratosis of conjunctiva clinically simulating a malignant melanoma. Design: Case report. Methods: A 66-year-old man presented with a juxtalimbal pigmented tumor inv olving the temporal conjunctiva of his left eye. Because of the rapid enlar gement of the mass within a period of 5 months, a clinical diagnosis of mal ignant melanoma was made. Cytopathologic examinations were performed by imp ression cytology before the patient underwent a wide en-block excision of t he tumor. Main Outcome Measures: Cytologic features were studied by impression cytolo gy with periodic acid-Schiff-Papanicolaou stain. Immunochemical characteris tics of tumor cells were studied by immunochemical stain of cytokeratin and HMB-45, Tumor morphology was observed by histopathologic examination. Results: Impression cytology disclosed basaloid cells intermixing with squa moid cells, and these cells demonstrated positive immunoreactivity to cytok eratin and no reactivity to HMB-45. Histopathologic examination of the tumo r specimen established the diagnosis of seborrheic keratosis, and the resul ts of immunohistochemical staining were consistent with those of the impres sion cytology with immunocytochemical staining. Conclusion: The authors describe the first case report of conjunctival sebo rrheic keratosis and present its immunocytochemical and immunohistochemical characteristics. Such a benign lesion can clinically mimic a malignant mel anoma.