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Background
Sonographic imaging plays a pivotal role in the assessment of subgaleal masses, particularly subgaleal lipomas, given their distinct echo and characteristic features. Accurate differentiation from other mass mimickers, such as hematoma, dermoid, multiple myeloma, and liposarcoma, is crucial for appropriate clinical management. This exhibit aims to elucidate the ultrasound findings that enable the differentiation of subgaleal lipomas from these mimicking entities, enhancing diagnostic accuracy and guiding effective patient care. Furthermore, the exhibit will explore the potential role of ultrasound-guided biopsy in confirming subgaleal lipoma diagnoses, contributing to improved diagnostic precision and patient care.

Educational Goals / Teaching Points
Provide a comprehensive overview of subgaleal lipomas, encompassing a review of scalp anatomy and pathological findings. Examine the ultrasound imaging technique and sonographic characteristics inherent to subgaleal lipomas, synergizing with MRI and CT correlations to offer a comprehensive diagnostic panorama. Delve into the differential diagnoses for cranial masses, neoplasms, and potential pitfalls, fostering a refined acumen in discerning these entities. Offer a treatment overview and provide valuable radiologic dictation insights to aid in diagnostic precision.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Subgaleal lipomas occur between the galea aponeurotica and calvarial periosteum, often presenting as palpable masses. In contrast to typical lipomas, the tightly contained location renders the mass firm and fixed, masking the clinical diagnosis. Subgaleal lipomas are readily diagnosed by ultrasound, obviating the need for unnecessary CT or MRI. Sonographically, subgaleal lipomas are well-defined, lens-shaped masses with an isoechoic appearance to the adjacent fat and internal parallel thin echogenic lines with an echogenic rim of fibrous tissue. On Doppler imaging, there is no increased flow. Dynamic ultrasound confirms malleability and offers a radiation-free, cost-effective, high-resolution, and efficient evaluation. Although these imaging findings strongly indicate subgaleal lipomas, definitive diagnosis may necessitate histopathological confirmation, particularly in cases with atypical features or diagnostic uncertainty. In such instances, ultrasound-guided biopsy offers an efficient diagnostic approach. Moreover, precise differentiation from other subgaleal masses or mimickers remains pivotal for optimal management.

Conclusion
This exhibit underscores the significance of ultrasound imaging in the evaluation of subgaleal lipomas and aids in distinguishing them from mimicking entities. By thoroughly exploring the sonographic characteristics, alongside pertinent MRI and CT correlations, attendees are equipped with an enriched diagnostic toolkit. Through the collective understanding of differential diagnoses and potential pitfalls, we empower practitioners to navigate the diagnostic process more effectively. Furthermore, in situations where accurate imaging diagnosis is uncertain, ultrasound plays a role in imaged-guided biopsy for definitive histopathologic diagnosis.