Malignant and benign lesions of the skeletal musculature

Translational research in diagnosis and management of soft tissue tumours

Finding a soft tissue mass in the superficial regions is a common event in daily clinical practice. Correct management of the diagnostic process is crucial to avoid blunders. Diagnosis is posed by pathology, although both imaging and a better understanding of the cellular and molecular mechanisms play an important a role in the characterization, staging and follow-up of soft tissue masses. Cellular and molecular mechanisms can explain either the development of chemo-resistance and the underlying pre- and post-surgery metastasis formation. These are mandatory to improve prognosis and unveil novel parameters predicting therapeutic response. Imaging mainly involves ultrasound and MR and is fundamental not only in diagnosis but also in the first step of therapy: the biopsy. Novel imaging techniques like Ultrasound Elastosonography, Dynamic Contrast-Enhanced MR imaging (DCE), Diffusion Weighted MR imaging (DWI) and MR Spectroscopy (MRS) are discussed. This paper aims at reviewing and discussing pathological methods and imaging in the diagnosis of soft tissue masses underscoring that the most appropriate treatment depends on advanced molecular and radiological studies.

Intramuscular plasmacytoma

OBJECTIVE

In multiple myeloma, secondary infiltration of adjacent muscles from bone lesions is common. However, plasmacytoma directly arising within the skeletal musculature is rare. Imaging findings of this rare entity have been described only sporadically. The purpose of this study was to identify the clinical signs and radiological features of intramuscular plasmacytoma (IP).

MATERIALS AND METHODS

Eleven patients with IP were retrospectively identified in the pathological and radiological databases of our institution. Computed tomography (CT) was performed in nine patients and magnetic resonance imaging (MRI) in four cases.

RESULTS

IP presented clinically with local pain in four patients. In one case with involvement of the rectus lateralis muscle of the eye, the patient showed a painless bulbus proptosis. In another patient, IP manifested as a massive bilateral forearm swelling with compartment syndrome. In four patients, IP was identified incidentally on computed tomography during staging examination. On imaging, two patterns of IP were found: intramuscular mass (n = 5) or diffuse muscle infiltration (n = 6). On CT with contrast, IP showed a moderate enhancement. With MRI on T1-weighted images, IP was isointense in comparison to the unaffected musculature, whereas on T2-weighted images, IP showed high signal intensity. After intravenous administration of contrast medium, a slight-to-moderate inhomogeneous enhancement was seen in all cases.

CONCLUSIONS

IP should be considered in the differential diagnosis of muscle tumors. It manifests with two radiological patterns, either as intramuscular mass or as diffuse muscle infiltration.