Retinoblastoma
is the most common intraocular tumor of childhood affecting approximately
one in twenty thousand live births. It
may be inherited as an autosomal dominant trait with incomplete penetrance
(possibly a deletion in the area of chromosome 13q14) or may arise as a
sporatic form. The tumor may
present clinically as leukocoria(#22140), strabismus, red eye, change in
color of iris, spontaneous hyphema, pseudohypopyon, and ocular enlargement
because of glaucoma. Retinoblastoma
is thought to arise from primitive neural elements of the retina rather
than the glial elements. Histopathologically, this tumor may have one of
several growth patterns: exophytic (tumor grows into subretinal space
(#22141)), endophytic (toward the vitreous(#9847)), or as a mixture of
both patterns (common(#18762)). Dystrophic
calcification and necrosis are common (#22143). The tumor cells have large basophilic nuclei with scant
cytoplasm. Well
differentiated tumors have Flexner-Wintersteiner rosettes which consist of
a row of photoreceptor-like tumor cells arranged into a circular
pattern(#22146). The outer
segments of primitive rods and cones point toward the lumen.
The outer nuclear layer forms the cellular lining of the rosette.
These are essentially pathognomonic of retinoblastoma.
Fleurettes are tumor cells which show a great deal of
differentiation toward photoreceptors, but are arranged side-by-side.
Pseudorosettes are circumferential arrangements of viable
basophilic tumor cells around blood vessels(#22144).
Prognosis worsens with
(1) optic
nerve invasion(#22147), especially if present in the cut surface of the
enucleated optic nerve;
(2) absence
of Flexner- Wintersteiner rosettes indicating less differentiation;
(3)
choroidal invasion; or
(4) large
size, especially with vitreous seeding or extension anterior to the
equator. Retinoblastomas may
extend locally into the orbit(#22149) and directly invade the brain and
the central nervous system. In
addition, these tumors may show wide-spread metastases.
The treatment consists predominantly of enucleation of the involved
eye. In bilateral cases, the
eye with the larger tumor is often enucleated and the eye with the smaller
tumor is treated with radiation therapy.
Children with hereditary retinoblastomas also have a predeliction
for developing secondary malignancies, the most common of which is an
osteogenic sarcoma of the femur.
-See also
(#27773, #27776, #27779, #27785, #27791, #27794, #27806, #27824, #27827,
#27833, #27839, #27842, #27845, #27848, #27851, #46504) for other slides
of retinoblastoma. -(#27809, #27812, #27815, #27821) are all slides
showing rosettes associated with retinoblastoma.
