Clinicopathologic features of retinoblastoma after primary chemoreduction.

BACKGROUND Primary chemotherapy is a new treatment approach in retinoblastoma, aiming to avoid radiogenic adverse effects, such as second tumor-associated mortality, as observed following external beam irradiation. OBJECTIVE To describe the clinical and histopathologic regression pattern after primary chemotherapy in retinoblastoma. METHODS Five patients with sporadic bilateral retinoblastoma underwent planned enucleation of their functionally blind eye after 2, 3 (in 2 patients), 4, and 6 courses of primary chemotherapy with carboplatin, etoposide, cyclophosphamide, and vincristine. The eyes were examined histopathologically, using light microscopy and immunohistochemical analysis with proliferation markers. RESULTS One patient had a type 1 (cottage cheese) regression and 4 patients had either a type 2 (fish flesh) or a type 3 (combined) regression pattern. Histopathologic examination revealed a complete tumor necrosis in 1 patient with type 1 regression after 3 courses of chemotherapy and in 1 patient with type 3 regression after 4 courses of chemotherapy. The remaining 3 patients with type 2 or type 3 regression had histologically still active proliferative tumor cells after 2, 3, and 6 courses of chemotherapy. CONCLUSION This article correlates histopathologically the clinically described efficacy of primary chemotherapy in the treatment of retinoblastoma, underlining, however, the necessity of careful observation and the use of ancillary treatment whenever there is no complete tumor regression.