How to Diagnose Retinoblastoma

Introduction

A retinoblastoma is a malignant tumor of the eye. It is the most common form of eye cancer in children and is caused by a mutation on chromosome 13. A retinoblastoma is generally believed to arise from a multipotential precursor cell and exhibits three types of growth: endophytic, exophytic and diffuse infiltrating growth. The following steps will show how to diagnose a retinoblastoma.

Instructions

Difficulty: Challenging

Steps

1

Step One

Obtain a family history. Parents should be specifically questioned about eye tumors and other cancers in any family members. Patients with retinoblastoma have no family history 95 percent of the time.

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Step Two

Expect a retinoblastoma to have a large variety of presenting symptoms with a white papillary reflex the most characteristic. Squinting as a result of vision loss also is common and should prompt a fundoscopic examination through a dilated pupil. Laboratory tests may be used to eliminate other conditions similar to retinoblastomas.

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Step Three

Identify the retinoblastoma gene directly. DNA is taken from tumor cells or leukocytes and the gene is detected with karyotyping or Southern blotting.

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Step Four

Detect point mutations in the retinoblastoma gene with gel electrophoresis, direct DNA sequencing using polymerase chain reaction, ribonuclease protection or single-strand conformation polymorphism. Indirect methods may be used when the mutation can't be located. These methods detect DNA polymorphisms within the retinoblastoma gene.

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Step Five

Examine the suspect tumor histologically. Retinoblastomas characteristically exhibit Flexner-Wintersteiner rosettes and occasionally fleurettes. A Homer-Wright rosette is not suggestive because they are encountered in many neuroblastic tumors and few eye tumors show any glial differentiation.