To the Editor.
—Metastatic retinoblastoma is relatively uncommon in developed nations.1,2 Historically, this ocular neoplasm was uniformly fatal; however, early diagnosis and treatment have markedly decreased tumorrelated mortality. In major US ocular oncology centers second malignancies cause more deaths than metastases in germinal mutation cases; overall, less than 12% of patients develop widespread retinoblastoma.3Extraocular retinoblastoma is often difficult to diagnose, especially if it does not involve cranial structures. Most extraocular retinoblastomas are noted at the time of the initial eye tumor diagnosis and involve the contiguous orbit or brain.4,5 Isolated involvement of bone marrow is uncommon.4,6 Unlike intraocular tumors that are usually calcified, calcification is not seen in metastatic deposits. In other body locations, the small, round retinoblastoma cells are not readily differentiated from other childhood malignancies, such as neuroblastoma, rhabdomyosarcoma, lymphoma, or Ewing's sarcoma.A number of advances in immunohistology may help increase diagnostic accuracy
Char D, Kaleta-Michaels S, Engman E. Metastatic Retinoblastoma. Arch Ophthalmol. 1989;107(11):1570-1571. doi:10.1001/archopht.1989.01070020648011