Cyst with Nodule

Troy Hutchins, MD

Karen L. Salzman, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Cystic lesions with solid nodular components can be divided into 2 categories
- Lesions that typically demonstrate cyst with nodule morphology
  - Neurocysticercosis (NCC), pilocytic astrocytoma, ganglioglioma, hemangioblastoma, pleomorphic xanthoastrocytoma (PXA), desmoplastic infantile ganglioglioma (DIG), intraparenchymal schwannoma
- Lesions that may demonstrate cyst with nodule morphology
  - Metastases, glioblastoma multiforme (GBM), abscess, toxoplasmosis, parasites, DNET, thrombosed AVM
Although metastases, abscesses, & GBMs do not classically present as “cysts with nodules”, they are included because of their overall prevalence
- Statistically, the atypical form of these common diseases may be more likely than some of the other “classic” cyst with nodule lesions

Helpful Clues for Common Diagnoses

Neurocysticercosis
- Cyst with “dot” inside representing scolex
- Imaging appearance varies with stage; increased enhancement & edema when organism dies (inflammatory host response)
- Location: Convexity subarachnoid space > > cisterns > parenchyma > ventricles
Pilocytic Astrocytoma
- Cerebellar cystic mass with mural nodule in a child; rarely supratentorial
- T1 C+: Nodule shows intense but heterogeneous enhancement
Ganglioglioma
- Cortically based, slow-growing enhancing mass in older child or young adult
- Cyst with nodule most common, may be solid
- Most common tumor to cause temporal lobe epilepsy
Hemangioblastoma
- Parenchymal posterior fossa cyst with nodule mass in an adult
- T1 C+: Nodule abuts pial surface & shows intense, homogeneous enhancement
- Multiple in von Hippel-Lindau syndrome (VHL) (25-40% of hemangioblastomas)

Helpful Clues for Less Common Diagnoses

Metastases, Parenchymal
- Discrete, gray-white interface mass(es) with adjacent vasogenic edema
- Multiplicity, history of primary malignancy, helpful if present
- Solitary metastasis may mimic GBM
Glioblastoma Multiforme
- Malignant white matter mass with central necrosis
- Predilection to spread across midline along corpus callosum; “butterfly glioma”
- T1 C+: Thick, irregular, nodular enhancing margins
- T2/FLAIR: Surrounding hyperintensity & mass effect reflect edema + infiltrative tumor
Pleomorphic Xanthoastrocytoma
- Cortically based cyst + nodule ± involvement of adjacent meninges
- T1 C+
  - Enhancing nodule
  - Look for thickening, enhancement of adjacent meninges
  - 70% have “dural tail”
- Temporal lobe predominance; young adult
Abscess
- T2 Hypointense rim with surrounding edema classic
- T1 C+: Enhancing capsule thinnest at ventricular side
- DWI: Cystic component bright (diffusion restriction)
Opportunistic Infection, AIDS, Toxoplasmosis
- Toxoplasmosis: Enhancing central nodules with peripheral rim = “target” lesions
- Location: Basal ganglia > hemispheres
- Clinical: Immunocompromised patient
Parasites, Miscellaneous
- Multiple enhancing lesions typical
- May mimic brain tumor
- Travel history critical
DNET
- Bubbly, wedge-shaped, cortically based mass “points” toward lateral ventricle
- T2: Very hyperintense; nodular, septate; no surrounding edema
- T1 C+: No to minimal enhancement, may be nodular
- Temporal lobe predominance

Helpful Clues for Rare Diagnoses

Desmoplastic Infantile Ganglioglioma
- Supratentorial cystic/nodular mass with dominance of the cyst
- Cortically based nodule with intense enhancement & dural tail
- May be massive
- Peak age 3-6 months
Schwannoma, Intraparenchymal
- Only 1-2% of schwannomas are parenchymal
- Cyst with strongly enhancing nodule
Arteriovenous Malformation (AVM)
- When hemorrhagic with partial or complete thrombosis, may present as cyst with nodule
- Blood breakdown products of various ages; fluid-fluid levels

Alternative Differential Approaches

By location
- Posterior fossa: Pilocytic astrocytoma, hemangioblastoma, metastasis
- Temporal lobe: Ganglioglioma, pleomorphic xanthoastrocytoma, DNET
- Gray-white junction: Metastases, abscess
- Hemispheric: NCC, Metastases, GBM, infections, DIG, AVM
Patient age
- Child & young adult: Pilocytic astrocytoma, ganglioglioma, PXA, DNET
- Adult: Hemangioblastoma, GBM, metastases
- Any age: Neurocysticercosis, abscess, other infections
Multiple lesions
- Metastases (50-55%), NCC (50-70%), hemangioblastoma (VHL), abscesses (septic emboli), toxoplasmosis, parasites