Punch biopsy of iris lesions: a novel technique for obtaining histology samples

To obtain iris biopsy samples of sufficient quality and quantity for histopathological analysis using a novel punch biopsy technique.

Two patients underwent iris tumour biopsy at an ocular oncology service. A trabeculectomy punch (Kelly Descemet's membrane punch) with a 1.0 mm diameter head and a 0.75 mm deep bite was inserted through a clear cornea perforated by a SatinSlit 3.2 mm angled slit knife into a viscoelastic-filled anterior chamber. The Kelly punch was placed over the lesion and pressed down before the punch was made. After obtaining the sample, the Kelly punch was removed from the eye and then opened over a dry cellulose sponge. Tissue samples were placed in 4% formalin and processed routinely for standard staining with H&E, periodic acid Schiff and immunostains.

In both patients, by using the punch biopsy technique with the Kelly punch, we were able to obtain a 0.8 x 0.6 mm piece of tissue, large enough for any histological analysis. H&E staining showed spindle cell melanoma. Tissue sections, stained positive with MART-1 (melanoma antigen recognised by T cells) and negative with cytokeratin, established the diagnosis of melanoma of the iris in each of these patients.

Iris biopsy with the punch technique yields a tissue biopsy specimen, as opposed to cytology samples obtained by fine needle aspiration biopsy. This technique is quick, simple to perform and requires non-expensive and easily available equipment. The tissue obtained is of sufficient quality and quantity to enable routine and special stainings.