From the Guidelines
For subcutaneous lumps on the abdomen and groin that are visible, growing in size, non-tender, and without signs of infection, ultrasound is the best initial imaging study to order. This recommendation is based on the high sensitivity and specificity of ultrasound in assessing superficial soft-tissue masses, as demonstrated by Hung et al 1, with an overall sensitivity and specificity of 94.1% and 99.7%, respectively. The use of ultrasound as the initial diagnostic imaging method is supported by its ability to accurately identify characteristic features of superficial or subcutaneous lipomas, such as no or minimal acoustic shadowing, no or minimal vascularity, and simple curved echogenic lines within an encapsulated mass 1.
Some key benefits of using ultrasound for initial assessment include:
- Non-invasive nature
- Lack of radiation
- Excellent visualization of soft tissue masses
- Ability to differentiate between solid and cystic lesions
- Capability to determine the depth, vascularity, and relationship of the masses to surrounding structures 1
If the ultrasound findings are atypical or inconclusive, further imaging with MRI or CT may be necessary to better characterize the masses and guide further management, which may include biopsy for definitive diagnosis 1. However, given the high accuracy of ultrasound for superficial masses, it is the most appropriate initial imaging modality for this patient's presentation.
From the Research
Imaging Options for Subcutaneous Lumps
- The patient presents with subcutaneous lumps on the abdomen and groin area, which are visible and growing in size, but not painful to touch and show no visible signs of infection.
- The best initial imaging modality to order for these superficial soft tissue masses is ultrasound (US) 2, 3, as it is an ideal triaging tool for superficial soft tissue masses.
- High-frequency ultrasound (HFUS) has been shown to be particularly useful in evaluating subcutaneous lesions, with a significant improvement in diagnostic accuracy when combined with clinical examination 4.
- US is preferred over magnetic resonance imaging (MRI) for initial evaluation due to its availability, low cost, and safety 2.
- If the US findings are indeterminate or suggestive of malignancy, further imaging with MRI or biopsy may be necessary 2, 3.
Characteristics of Soft Tissue Masses
- The majority of soft tissue masses are benign, with lipomas being the most common type 2, 5.
- The differential diagnosis of soft tissue masses can be limited by considering the age of the patient, anatomic location of the lesion, salient imaging features, and clinical manifestations 6.
- Fat-containing soft tissue masses, such as lipomas and liposarcomas, can be characterized by their appearance on MRI, but distinguishing between benign and malignant lesions can be challenging and may require histologic evaluation 5.