Tapioca melanomas of the iris: immunohistology and report on two cases

Abstract 

· Background: Tapioca-like tumors are rare, and their benign or malignant nature is obscure without histological work-up. We report on the clinical and histological features of different types of tumors in two patients. · Case report: Two patients aged 17 and 45 years presented with brownish iris masses increasing in size. Full-thickness en bloc excision of melanocytic tumors (5.5 mm and 7.0 mm in diameter) was carried out. Histological work-up revealed a nevus cell nevus in the young patient and an epithelioid malignant melanoma in the middle-aged patient evolving from the ciliary body. Staining for HMB-45 was marked in both tumors, for S-100 low in the nevus and marked in the melanoma, and for p53 negative in the nevus and positive in the melanoma. Ki67 stains were negative. · Conclusion: We propose that excision of anteriorly located pigmented tumors that increase in size is indicated in order to deter-mine whether they are benign or malignant. In these case reports, tapioca-like tumors include a benign and a malignant entity. To our knowledge, a nevus cell nevus presenting as a tapioca-like tumor has not previously been described. Curative surgery and histological and immunohistological evaluation are required to characterize the malignant potential of these tumors and the prognosis.