Tumors of the orbit and eyeball

Malignant neoplasms in children

The two most significant pediatric tumors of this localization have completely different origins, but sometimes similar initial manifestations.

Retinoblastoma (Retinoblastoma) develops from immature retinal tissue due to disruption of the RB1 tumor suppressor gene (chromosome 13). Most often, the disease presents with leukocoria (absence of the red reflex of the eye). Hereditary forms occur at an earlier age, frequently affect both eyes, and are associated with a high risk of other tumors (e.g., osteosarcoma). There is also trilateral retinoblastoma syndrome, where ocular involvement is combined with neuroblastic tumors of the pineal or sellar regions.

• CT: The modality of choice for initial evaluation. A hyperdense mass in the posterior chamber of the eye is visualized, almost always (95%) containing calcifications.
• MRI: Sensitive for assessing intracranial extension. The tumor signal is similar to gray matter.

Rhabdomyosarcoma (Rhabdomyosarcoma) is the most common extraocular tumor in children (peak around 7 years). It is characterized by aggressive growth: causing rapidly progressive exophthalmos (proptosis) and eyelid edema. Due to a pronounced inflammatory reaction, both of these tumors can be misdiagnosed as orbital cellulitis.

• Unlike retinoblastoma, rhabdomyosarcoma does not calcify on CT. It has muscle density, enhances with contrast, and is accompanied by bone wall destruction and extension into the nasal sinuses.

Tumor lesions in adults

In adult patients, lymphoproliferative disorders and melanoma come to the forefront.

Primary orbital lymphoma is most commonly represented by low-grade MALT lymphoma. The peak incidence occurs between 50 and 70 years of age. The tumor usually affects the lacrimal gland or ocular adnexa, developing insidiously and causing painless eye protrusion and diplopia. An important clinical rule: even if the process appears isolated, the patient must undergo whole-body scanning, as the orbit may be only the first "target" of systemic lymphoma. Secondary orbital involvement in the setting of a known non-Hodgkin lymphoma is rare (less than 2% of cases).

• Imaging findings: On CT, lymphoma may be hyperdense. On MRI, there is a decreased signal on T1-weighted images and active gadolinium enhancement. Bone destruction is atypical for lymphoma (occurs only in high-grade malignancies).

Choroidal melanoma (Choroidal Melanoma) on MRI is most frequently visualized as a nodular mass (e.g., on the nasal side of the eyeball). On T1 images, concomitant retinal hemorrhage may be detected, and PET-CT demonstrates focal radiopharmaceutical uptake.

Leukemic infiltration and metastases

Orbital involvement can be a consequence of leukemia (both myeloid and lymphoblastic). The process manifests as diffuse infiltration or a focal mass (chloroma in acute myeloid leukemia). The most common ocular complication of leukemia remains secondary retinal hemorrhage due to concomitant thrombocytopenia. Infiltration of the optic nerve by leukemic cells is an oncological emergency due to the risk of irreversible blindness.

Metastatic involvement of the orbit can have various routes of spread:

1. Direct invasion: For example, extensive extension of paranasal sinus carcinoma into the orbit through the lamina cribrosa.
2. Hematogenous route: Prostate carcinoma metastasis can form in the area of the sphenoid triangle, which on bone window CT manifests as pronounced sclerosis and bone expansion, and on soft tissue window as a soft tissue component displacing the eyeball.

Medulloepithelioma

Medulloepithelioma (Medulloepithelioma) is a rare embryonal tumor (can be both benign and malignant). It arises from the ciliary body epithelium, usually in children around 5 years of age. On CT, it may have increased density, contain areas of cartilaginous tissue and dystrophic calcifications. The key to diagnosis is tumor localization in the projection of the ciliary body. However, if the process is massive and infiltrates the retina, the imaging appearance becomes virtually indistinguishable from retinoblastoma.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Imaging semiotics of orbital trauma (wall fractures, orbital compartment syndrome)
• Diagnosis of orbital foreign bodies (metal, glass, wood) on CT and MRI
• Signs of globe rupture (flat tire sign, volume loss)
• Retinal and choroidal detachment: imaging differentiation
• Ischemic optic neuropathies (AION)

Other topics in the Neuroimaging section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.