Non-Malignant Causes of Non-Painful Skull Mass in Elderly Females
The most common non-malignant causes of a skull mass in an elderly female are meningioma (representing >30% of CNS tumors), followed by intraosseous meningioma, epidermoid cysts, and rarely benign smooth muscle tumors like leiomyomas or angioleiomyomas. 1, 2
Primary Benign Differential Diagnoses
Meningiomas (Most Common)
- Meningiomas account for more than 30% of all CNS tumors and are the most frequent benign skull lesion, with a female-to-male ratio of 2-3:1 and median diagnosis age of 65 years. 1
- These tumors develop from meningothelial cells and commonly occur at parasagittal/falcine, convexity, sphenoid ridge, suprasellar, and skull base locations. 1
- Grade I (benign) meningiomas represent the vast majority of cases with >80% ten-year survival, though their location can still cause significant morbidity. 1
- On imaging, meningiomas typically appear isointense on T1 and T2 MRI with homogeneous enhancement and may show a characteristic dural tail sign. 2
Intraosseous Meningioma
- Intraosseous calvarial meningiomas are rare variants confined to the skull bone itself, typically exhibiting osteoblastic activity but occasionally presenting as purely lytic lesions. 3
- These can radiologically mimic malignant processes like osteosarcoma, making biopsy essential for diagnosis. 4
- The frontoparietal and orbital regions are most commonly affected, with average diagnosis age around 50 years. 4
- Complete surgical excision offers excellent prognosis without recurrence. 3
Leiomyomas and Angioleiomyomas
- Skull base leiomyomas (LMs) and angioleiomyomas (ALMs) are extremely rare benign smooth muscle tumors that are usually painless and occur more commonly in females. 2
- ALMs represent <1% of head and neck tumors, with only 39 total intracranial cases reported in the literature (19 in skull base). 2
- These lesions can be large (up to 7.7 cm) and locally destructive but are benign with excellent prognosis after resection. 2
- Malignancy is extremely rare when these pathologic entities are diagnosed, and they show universally low mitotic activity with no reported recurrences even after subtotal resection. 2
- On imaging, ALMs appear hypointense/isointense on T1, isointense to hyperintense on T2, and hyperdense on CT with variable contrast enhancement. 2
Other Benign Considerations
- Epidermoid cysts, lipomas, and arachnoid cysts represent less frequent benign skull base lesions. 2
- Fibrous dysplasia, Paget's disease, and hemangiomas should be considered based on imaging characteristics. 5
- Eosinophilic granuloma presents as an osteolytic lesion with characteristic bevelled edges. 5
Critical Diagnostic Pitfalls
Radiological Mimicry of Malignancy
- Benign lesions can demonstrate radiological features suggesting malignancy, making tissue diagnosis essential before definitive treatment. 4
- Intraosseous meningiomas may show lytic and sclerotic regions with irregular cortex that mimics osteosarcoma on CT. 4
- ALMs may show a dural tail sign, prompting misdiagnosis as meningioma, and their vascular nature can complicate surgical resection. 2
Age-Related Considerations
- While meningiomas have a median diagnosis age of 65 years, intraosseous variants average 50.5 years, and skull base ALMs typically occur between ages 40-60. 1, 4, 2
- In elderly patients with small asymptomatic tumors, observation with serial imaging is appropriate, with treatment initiated only upon progression. 6
Imaging Approach
MRI as Primary Modality
- MRI with and without IV contrast is the critical imaging modality for surgical and radiation treatment planning due to excellent soft tissue contrast and high spatial resolution. 2
- Standardized protocols should include 3D T1 pre- and post-contrast, T2 FLAIR, diffusion-weighted imaging, and susceptibility-weighted imaging. 2
CT for Surgical Planning
- CT without contrast provides essential information about osseous involvement, erosions, and hyperostosis that guides surgical approach. 2
- Presence of osseous erosions is uncommon in meningiomas and should raise consideration of alternative diagnoses. 2