Rapid cytologic diagnosis of choroidal malignant melanoma by vitreous smear

The eye is an uncommon subject of cytopathological examination. However, cytopathologic examination may be required for definitive diagnosis in some cases, as malignant tumors of the eye may sometimes be difficult to distinguish clinically from benign disorders. We report a case of malignant melanoma (MM) of the choroid, in which vitrectomy was performed for the initial clinical diagnosis of vitreous hemorrhage. As the dense vitreous hemorrhage was gradually cleared during the vitrectomy, a choroidal mass was discovered and the vitreous fluid was procured for rapid cytologic diagnosis. We used a modified Shorr's stain that can be completed within several minutes. With this method, highly atypical, pleomorphic cancer cells, occasionally associated with melanin pigment granules, were demonstrated. These cytologic findings indicated a diagnosis of MM arising from the choroid. Histologic examination of the enucleated eye confirmed MM of epithelioid type. The advantage and indication of the rapid cytologic diagnosis is discussed.