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

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 determine 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.