Imaging Algorithm for Shoulder Soft‑Tissue Masses

Initial Radiographic Evaluation

The American College of Radiology recommends obtaining plain shoulder radiographs (at least two views) as the first imaging step for any soft‑tissue mass, because radiographs reveal positive findings in 62 % of proven lesions, most commonly calcification (27 %), bone involvement (22 %) and intrinsic fat (11 %)【1】.
Radiographs can provide a definitive diagnosis for characteristic entities such as phleboliths in hemangiomas, synovial chondromatosis, and myositis ossificans, and they also identify unsuspected skeletal abnormalities, foreign bodies, and adjacent bone changes【1】【2】.

For small lesions located above the deep fascia, the American College of Radiology advises using high‑frequency ultrasound, which demonstrates a sensitivity of 94.1 % and specificity of 99.7 % for detecting benign soft‑tissue masses【2】【3】.
Ultrasound is most accurate for characterizing lipomas, followed by vascular malformations, epidermoid cysts, and peripheral nerve sheath tumors【2】【3】.
The modality is valuable for distinguishing solid from cystic lesions and for evaluating the relationship of the mass to surrounding neurovascular structures【1】【2】.
If ultrasound findings or clinical features are atypical, the American College of Radiology requires escalation to magnetic resonance imaging (MRI) for further assessment【2】【3】.

MRI without contrast is indicated when the mass is deep (below the deep fascia), when the lesion is not clearly superficial, or when prior ultrasound is indeterminate【1】【2】.
Although MRI is superior for characterizing deep masses and delineating their extent, it should not be used as the sole initial examination because it has limited sensitivity for detecting mineralization; radiographs must be performed first【1】【3】【4】.
Optimal evaluation of deep soft‑tissue masses therefore combines MRI findings with the information obtained from initial radiographs【1】【5】.

The American College of Radiology advises that computed tomography (CT) is not routinely ordered for the initial work‑up of soft‑tissue masses; CT may be reserved for cases where detailed assessment of complex osseous anatomy or precise mineralization characterization is required after radiography【1】【3】【4】.
Positron‑emission tomography/CT (PET/CT) is also not appropriate for the initial evaluation of soft‑tissue masses【1】【3】【4】.

Step 1: Obtain shoulder radiographs (minimum two orthogonal views).【1】【2】
Step 2: If the mass is clearly superficial/subcutaneous, proceed to ultrasound.
- When ultrasound shows typical benign features (e.g., a lipoma), further imaging is often unnecessary【3】.
- If ultrasound is atypical or inconclusive, obtain MRI without contrast【2】【3】.
Step 3: If the mass is deep or its location is uncertain, proceed directly to MRI without contrast after the radiographs【1】【2】【5】.

Approximately 96 % of superficial shoulder masses are benign; however, atypical imaging or clinical features mandate advanced imaging (MRI) to exclude malignancy【2】【3】.
Radiographs may be unrevealing for small, deep‑seated, non‑mineralized lesions or in anatomically complex regions, underscoring the need for complementary imaging when necessary【1】【2】.
The American College of Radiology emphasizes that MRI should never be relied upon in isolation without prior radiographs because of its poor sensitivity for detecting mineralization【1】【3】【4】.