Well Circumscribed Cystic Lesions

Ovarian Cyst Miracle

Ovarian Cyst Miracle Guide Book By Carol Foster

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The most common clinical differential diagnosis of cystic orbital lesions includes dermoid cyst, colobo-matous cyst, teratoma, meningoencephalocele, lymphangioma, acquired inclusion cyst, chronic hematic cyst (cholesterol granuloma), mucocele, subperiosteal hematoma, and parasitic cyst.25 On MRI these lesions appear as well-defined, round to oval lesions with variable signal intensity depending on the composition of their content (Table 10.4).1,2,5,31

Dermoid cyst may have an homogeneous or heterogeneous, isointense to hyperintense signal with respect to the vitreous on Tl-weighted images.5 On T2-weighted images, the cyst may appear isointense or hypointense to the vitreous.5 Dermoid cyst may have a characteristic dumbbell configuration.5,25 The varying intensity pattern of dermoid cyst on nonenhanced MR studies may also be seen in the other cystic orbital lesions. However, fat-fluid level is characteristically seen in dermoid cyst.5 The oily portion of the cyst content appears in the nondependent portion of the cyst and the keratin and water content in the de

volving the superior rectus and levator palpebrae superioris muscles and the surrounding orbital fat. Incisional biopsy confirmed the diagnosis of B-cell malignant lymphoma.

pendent portion of the cyst lumen. A fluid-fluid level is suggestive of subacute hemorrhagic lymphangioma or hemorrhagic cyst.4,32

Lymphangioma appears as a well-circumscribed unicystic or multicystic, homogeneous, or heterogeneous mass.4,32 The lesion may show an isointense or hyperintense signal on Tl-weighted images and an isointense or hypointense signal on T2-weighted images with respect to the vitreous (Table 10.4). This MR pattern is likely to be secondary to prominent lymphatic channels containing clear fluid. The tendency of orbital lymphangiomas to present with recurrent hemorrhage makes them ideal for MRI evaluation by demonstrating fluid-fluid levels (Figure 10.6). The superior aspect of the cyst contains the methemoglobin released from the lysed erythrocytes: the dependent portion contains the settled cellular elements of the hemorrhage with intracellular methemoglobin.4,32

Mucocele may have a variable signal intensity depending on the chronicity of the cyst. The concentration of proteinaceous secretions increases, as do the viscosity of the secretions and the slow resorption of the water through the mucosa.5,33

After Gd-DTPA administration, no enhancement is documented within the lumen of the cyst (Table 10.4).2,5,31,32 The lack of enhancement within the le-

TABLE 10.4. MR Features of the Most Common Cystic Orbital Lesions on

Spin-Echo Sequences.

Lesion appearance and signal with respect to vitreous T1-Weighted image T2-Weighted image

Degree of lesion enhancement after Gd-DTPA

Dermoid cyst Epithelial cyst Mucocele

Hemorrhagic cyst/lymphangioma

Hetero

Iso/Hyper

Homo

Iso/Hyper

Homo

Iso/Hyper

Hetero

Iso/Hypo

Homo

Iso/Hypo

Homo

Iso/Hypo/Hyper Hetero

Iso/Hypo/Hyper

-/+

FIGURE 10.5. Ill-defined infiltrative orbital lesion with a radiological differential diagnosis including idiopathic orbital inflammation, metastasis, and malignant lymphoma. (A) Coronal precontrast and (B) postcontrast Tl-weighted images show an infiltrative lesion in-

volving the superior rectus and levator palpebrae superioris muscles and the surrounding orbital fat. Incisional biopsy confirmed the diagnosis of B-cell malignant lymphoma.

rtar i"J TS

OAy 12.2

FIGURE 10.6. Recurrent hemorrhagic orbital lymphangioma with fluid-fluid levels. Axial T2-weighted image shows a multicystic lesion with heterogeneous high signal intensities and fluid-fluid levels suggesting lysed and intact erythrocytes.

sion usually rules out a solid neoplastic process. Enhancement may be seen within the capsule and septae surrounding the cystic lesion. On Gd-DTPA-enhanced Tl-weighted images, the degree of enhancement of lymphangioma is variable.2,5,32

Orbital CT gives excellent information regarding the cystic features of the lesion because its density is similar to that of the vitreous.3,11,31,33 However cystic lesions with higher density (with a high content of protein, keratinaceous material, or blood products) may simulate solid, well-circumscribed orbital tumor.3,5,11 MR studies are more specific than CT in identifying tissue component within the cystic mass. The age of the patient, the clinical presentation, and the anatomic location of the cystic lesion will help the clinician or radiologist in the differential diagnosis.

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  • lemlem
    What is a well circumscribed cyst?
    1 year ago

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