Ultrasound in Large > 5 cm
In the absence of reliable evidence, it is the opinion of the work group that ultrasounds in large (>5 cm), deep soft tissues tumors are unlikely to adequately assess the benign or malignant nature of the lesion and should not be the imaging modality of choice.

Rationale
Although frequently utilized prior to advanced imaging, standard ultrasound evaluation of concerning masses does not preclude subsequent advanced imaging. As a screening tool, the purpose of an ultrasound evaluation would be to identify which lesions need further imaging and which can be definitively diagnosed as benign. While mostly moderate quality evidence evaluations have shown reasonable psychometrics using advanced techniques in the 80-90% accuracy range (Belli 2000, Chen 2015, Chen 2009a, Lagalla 1998, and Nagano 2015), these studies did not address whether such evaluations could stand alone without an MRI or CT in a prospective manner. Part of the general usefulness of ultrasound is its availability and low cost; if a patient will likely ultimately need an MRI or CT regardless, the rationale for adding additional cost and time for ultrasounds needs further support. A meta-analysis of high and moderate quality studies conducted for this CPG showed a sensitivity of 0.84 and specificity of 0.84 for determining the malignancy of a lesion based on several ultrasound techniques (Chen 2015, Belli 2000, Chen 2009a, Lagalla 1998, Nagano 2015). Many authors reporting on the utility of ultrasound do so only as an adjunct rather than replacement for other advanced imaging (De Marchi 2003, Furuta 2016, Lagalla 1998, Nagano 2015), in which case the patientderived value needs to be elucidated. Miller et al (2015) noted that ultrasound studies were generally considered by orthopaedic oncologists to be unhelpful prior to referral. It may be possible in the future that advanced ultrasound techniques could be first line imaging, with MRI ordered by the referral center (De Marchi 2015, Loizides 2012). It is the consensus recommendation that if a mass is less than 5cm, superficial, and not by critical structures (axilla, groin, popliteal fossa, over a subcutaneous bone) then a principled excisional biopsy without ultrasound evaluation is reasonable. Should a patient not desire removal but reassurance, ultrasound may be able to confirm cystic nature and allow observation in the absence of growth (Nagano 2015). Wagner et al (2013) noted high accuracy for lipomas with 96.9% specificity for superficial masses. In cases where the size or depth of the lesion cannot be determined by physical examination, ultrasound can provide anatomic location to guide further evaluation and treatment. It is the consensus recommendation that if a mass is greater than 5cm, or deep, or by critical structures then an ultrasound evaluation is unlikely to obviate the need for advanced imaging and may delay treatment or provide false reassurance. In particular circumstances, such as vascular malformations (Furta 2017), ultrasound can aid in making a diagnosis and avoiding a biopsy, but in this setting ultrasound could be ordered if desired by a referral center. Moderate and high-quality studies are evaluating means of distinguishing benign versus malignant soft tissue masses by ultrasound (eg., Pass 2017, Chen 2009 a, Chen 2009 b). However, it is the opinion of the work group that there is not yet sufficient sensitivity for malignancy or specificity for benignity for ultrasound evaluations to obviate the need for further advanced imaging for large or deep or precariously located lesions (Nagano 2015). In these suspicious circumstances, an ultrasound should not be required prior to obtaining an MRI. In other clinical situations, such as evaluating a possible soft tissue sarcoma recurrence, ultrasound may be an effective means of surveillance and directing a biopsy (Arya 2000). We did not find any literature discussing use of ultrasound in bone lesions and suggest that our recommendations apply only to soft tissue tumors.

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