Fig. 9.1
Schwannoma in the left orbit. (a) Axial CT image in soft-tissue window shows an ovoid, well-demarcated homogeneous isodense mass in the left orbit. The left supraorbital fissure enlarges (white arrow). (b) Axial T1WI MR reveals a slightly hypointense and homogeneous mass. (c) Axial T2WI MR reveals a hyperintense mass, extending posteriorly to cavernous sinus. (d) Axial T1C+ MR shows heterogeneous intense signal enhancement of the mass
Fig. 9.2
Schwannoma in the left orbit. (a) Axial T1WI MR reveals an isointense and homogeneous mass in the left orbit. (b) Axial T2WI MR reveals heterogeneous moderate intensity of the mass. (c) Axial T1C+ MR with fat suppression shows heterogeneous enhancement of the mass. Patches of unenhanced area are seen in the mass
9.1.4 Diagnostic Checklist
CT can clearly demonstrate the location of the smaller schwannomas and their relationship with adjacent structure, but it is difficult to distinguish the bigger schwannomas from the adjacent structure with the similar density. CT is also difficult to differentiate the bigger schwannomas from other tumors in orbit.
MRI can demonstrate the signal of the schwannomas and their relationship with adjacent structure clearly, and it is easy to differentiate the schwannomas from other tumors. The qualitative diagnosis can be initially got from MR appearance.
9.2 Metastasis
9.2.1 Pathology
- 1.
Unilateral or bilateral, but unilateral is more frequent.
- 2.
The metastasis may originate from any site of the body. The most frequent primary tumors are lung, breast, digestive tract, and prostate carcinoma (Rajabi et al. 2015).
9.2.2 Preferred Imaging Recommendations
- 1.
CT: CT scanning should be used when the patients with eye symptoms are suspected to have retrobulbar lesions.
- 2.
MRI: Depending on the clinical history together with bony changes on CT, the qualitative diagnosis of orbital metastasis can be made. MR scanning should be further performed for delineating the extension of the lesion.
9.2.3 Imaging Findings
- 1.
CT findings: Orbital metastasis mostly presents as a single soft-tissue mass in the orbital wall (Fig. 9.3a). The orbital wall may have osteogenic, osteolytic, or mixed bone destruction (Fig. 9.3b) with soft-tissue mass. The soft-tissue mass with necrosis may reveal heterogeneous density on CT imaging.
- 2.
MR findings: Orbital metastasis demonstrates bone destruction and signal loss of the bone marrow. The lesion shows heterogeneous isointensity on T1WI (Fig. 9.3c) and heterogeneous hyperintensity on T2WI (Fig. 9.3d). If there are cystic necrosis areas, areas with hypointensity on T1WI and hyperintensity on T2WI may be seen. The lesion presents inhomogeneous enhancement. The cystic necrosis areas don’t enhance.
Fig. 9.3
Orbital metastasis. (a) Axial CT image in soft-tissue window demonstrates the osteolytic bone destruction with soft-tissue mass in the left greater wing of sphenoid bone. The mass is poor-demarcated and heterogeneous density. (b) Coronal CT image in bone window reveals the lesion involving the lateral and inferior orbital wall and the posterolateral wall of maxillary sinus. (c) Axial T1WI MR reveals a variably isointense to hypointense mass. The greater wing of sphenoid bone has bone destruction and signal loss of the bone marrow. (d) Axial T2WI MR reveals a variably isointense to hyperintense mass. (e) Axial T1C+ MR with fat suppression shows heterogeneous enhancement of the mass. The necrosis areas don’t enhance. The tumor’s extension is delineated clearly
9.2.4 Diagnostic Checklist
CT scanning demonstrates the bone destruction with soft-tissue mass in the orbital wall. The diagnosis can be clarified from CT combining with clinic history.
MR scanning should be further performed for delineating the tumor’s extension. When metastasis is suspected, the additional specific examination should be performed to search for the primary tumor.
9.3 Rhabdomyosarcoma
9.3.1 Pathology
- 1.
Rhabdomyosarcoma is the primary orbital malignancy originating from mesoderm mesenchymal tissue.
- 2.
Gross pathology shows fresh-red or slightly yellow mass with smooth surface and without connective tissue capsule.
- 3.
Rhabdomyosarcomas are classified into three histologic types: embryonal, alveolar, and pleomorphic, with the embryonal accounting for 2/3.
9.3.2 Preferred Imaging Recommendations
- 1.
CT: CT scanning should be used when the patients with rapidly progressing eye symptoms are suspected to have retrobulbar lesions.
- 2.
MRI: When the intraorbital mass is detected by CT, MR scanning should be further performed for delineating the extension of the lesion.
9.3.3 Imaging Findings
- 1.
CT findings: The tumor shows slight heterogeneous, poor-defined lobulated soft-tissue mass with adjacent osteolytic bone destruction (Fig. 9.4a, b). If there are cystic necrosis areas, hypodense patches may be seen.
- 2.
MR findings: Orbital rhabdomyosarcomas demonstrate heterogeneous isointensity and hypointensity on T1WI (Fig. 9.4c) and heterogeneous hyperintensity on T2WI (Fig. 9.4d) with bone destruction. The lesions present moderate to marked enhancement. The patches of unenhanced cystic necrosis areas may present (Fig. 9.4e, f) (Mu et al. 2014).
Fig. 9.4
Orbital rhabdomyosarcoma. (a) Axial CT image in soft-tissue window reveals large irregular soft-tissue mass in the left orbit. The mass is poor-demarcated and heterogeneous density. The tumor extends into the left ethmoid sinus. (b) Coronal CT image in bone window reveals bone destruction in the medial orbital wall. The lesion extends into the ethmoid sinuses and the nasal cavities. The lesion has indistinct margins with intraorbital structures. (c) Axial T1WI MR reveals a heterogeneous isointense mass in the left orbit. The intraorbital structures are compressed. (d) Axial T2WI MR reveals a heterogeneous hyperintense mass. (e) Axial T1C+ MR with fat suppression shows heterogeneous moderate enhancement of the mass. The tumor is poor-demarcated. (f) Coronal T1C+ MR reveals parameningeal rhabdomyosarcoma widely extending into the orbit and nasal cavities
9.3.4 Diagnostic Checklist
CT can clearly demonstrate the location and the adjacent bone erosion of the rhabdomyosarcoma. The boundary of the tumor is unclear for the similar density with adjacent soft tissue.
MR can reveal the signal characteristics of the tumor and the relationship with adjacent structures. The qualitative diagnosis can be initially got from tightly combing the clinical profile with CT and MR imaging.
9.4 Chloroma
9.4.1 Pathology
- 1.
Chloroma is also called granulocytic sarcoma, which is a special kind of acute myelogenous leukemia.
- 2.
The disease is called chloroma because the myeloperoxidase with the tumor imparts a green hue to it after exposure to air.
- 3.
Chloroma can arise at any part of the body. The skull base and orbit are frequently involved.
- 4.
The type M5 is the common subgroup of extramedullary infiltration of acute myelogenous leukemia (Ke et al. 2011).
9.4.2 Preferred Imaging Recommendations
- 1.
CT: CT scanning should be used when the patients with relative eye symptoms are suspected to have retrobulbar lesions.
- 2.
MRI: When the lesion is detected by CT, MR scanning should be further performed for delineating the extension of the lesion and the relationship with adjacent structure.
9.4.3 Imaging Findings
- 1.
CT findings: Orbital chloromas typically involve extraconal space (Fig. 9.5a) and can present as single or multiple masses involving the craniofacial bones (Fig. 9.5b), with osteolytic bone destruction or bone remodeling. Radial bone spicule is seldom seen (Fig. 9.5c).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
