MR imaging of clear cell sarcoma (malignant melanoma of the soft parts): a multicenter correlative MRI-pathology study of 21 cases and literature review

Abstract

nal intensities on T1-and T2-weighted images, contrast enhancement, relationship with adjacent fascia or tendon, secondary bone involvement, and intratumoral necrosis. In 19 cases the pathology findings were available for review and for a comparative MR-pathology study.Results. On T1-weighted images, lesions were isointense (n=3), hypointense (n=7) or slightly hyperintense to muscle (n=11). Immunohistochemical examination was performed in 17 patients. All 17 specimens showed positivity for HMB-45 antibody. In nine of 11 lesions with slightly increased signal intensity on T1-weighted images, a correlative MR imaging-pathology study was possible. All nine were positive to HMB-45 antibody. Conclusions. Clear cell sarcoma of the musculoskeletal system often has a benign-looking appearance on MR images. In up to 52% of patients, this lesion with melanocytic differentiation has slightly increased signal intensity on T1-weighted images compared with muscle. As the presence of this relative higher signal intensity on T1-weighted images is rather specific for tumors displaying melanocytic differentiation, radiologists should familiarize themselves with this rare entity and include it in their differential diagnosis when confronted with a well-defined, homogeneous, strongly enhancing mass with slightly higher signal intensity compared with muscle on native T1-weighted images. Abstract Objective. To evaluate MR imaging and pathology findings in order to define the characteristic features of clear cell sarcoma of the soft tissues (malignant melanoma of the soft parts). Design and patients. MR examinations of 21 patients with histologically proven clear cell sarcoma of the musculoskeletal system were retrospectively reviewed and assessed for shape, homogeneity, delineation, sig- Key words

Soft tissue sarcomas at a glance: clinical, histological, and MR imaging features of malignant extremity soft tissue tumors

“…On MRI clear cell sarcomas usually present as well-circumscribed lesions with variable SI on T1WI and T2WI. About 50% of tumors are slightly hyperintense to muscle on T1WI, probably due to the presence of melanin, and markedly hyperintense to muscle on T2WI [34]. Hourani et al suggested that clear cell sarcoma should be suspected in a lesion which displays high SI on all sequences, including fat-sat techniques [35].…”

“…As clear cell sarcomas are often well-defined and homogeneous and rarely show bone destruction or necrosis, they are often misdiagnosed as benign lesions [10,31,[33][34][35][36] (Fig. 8).…”

Malignant melanoma is genetically distinct from clear cell sarcoma of tendons and aponeurosis (malignant melanoma of soft parts)

“…The tumours are usually intimately associated with fascial or tendoaponeurotic structures but may regularly involve the subcutis and dermis by direct extension. Radiologically the lesion is often mistaken for a benign process (De Beuckeleer et al, 2000). CCS is characterized by repeated local recurrence and, with time, metastasizes primarily to lymph nodes, the lungs and bone; 5 and 10 year survival is variable but is in the order of 50% and 10 -20%, respectively.…”

A Slow-growing Prepatellar Mass in a 31-year-old Woman

“…Melanin has paramagnetic effects, resulting in shortening of T1 and T2 and thereby a high signal intensity on T1-weighted images and a low signal intensity on T2-weighted images. High signal on T1-weighted images can be used to distinguish a clear cell sarcoma from most other soft tissue tumors that lack the presence of melanin [1]. However, increased intensity on T1-weighted images is certainly not pathognomonic for melanin, since it also indicates the presence of fat, blood, or certain stages of proteinaceous material.…”

“…Conventional radiographic examination shows a noncalcified mass and is noncontributory in most cases [1,6,8]. Involvement of underlying bone is rare but has important clinical implications when present [2].…”