Magnetic resonance imaging features of alveolar soft part sarcoma: report of 14 cases

Abstract

Background: The purpose of this study was to assess the magnetic resonance imaging findings of alveolar soft part sarcoma.

Methods: Magnetic resonance images of pathologically proven alveolar soft part sarcoma in 14 patients were retrospectively reviewed, including lesion location, size and shape, border definition, signals on T1-weighted and T2-weighted images, presence or absence of peritumoral and intratumoral flow voids, and enhancement pattern.

Results: Patients included five women and nine men, ranging in age from 27 to 54 years, with a mean age of 36 years. A slow-growing mass without pain was the chief complaint. Eight patients had pulmonary metastases at presentation. Ten lesions arose from the extremities, two were located in the gluteal regions, one affected the presacral space and one occurred in the back. The mean maximal size of the lesions was 9.8 cm, ranging from 6.2 to 16 cm. All lesions appeared as a round (n = 2), ovoid (n = 8) or irregular (n = 4) shape with ill-defined margins. The lesions mainly demonstrated isointense or mildly hyperintense compared to muscle on T1-weighted images, and heterogeneous high signal intensity on T2-weighted images. Peritumoral edemas were observed in six patients. Ten lesions showed intense inhomogeneous enhancement after contrast. Intra- and peritumoral tubular flow voids representing tortuous dilated vessels with rapid blood flow were present in all cases.

Conclusions: Alveolar soft part sarcoma has some distinctive magnetic resonance imaging features including a slow-growing, large mass in the soft tissue of the extremities in young adults, with numerous signal voids on T1-weighted and T2-weighted images, and strong enhancement after contrast.

Figure 1

A 25-year-old man with alveolar soft part sarcoma. (a) Coronal T1-weighted image shows a hyperintense signal tumor in the right lower calf with an ill-defined margin in a 25-year-old man. There are tortuous intra- and extratumoral signal voids (arrows). (b) Coronal T2-weighted image and (c) coronal fat-suppressed T2-weighted image reveal the hyperintense signal tumor with intra- and extratumoral signal voids (arrows). (d) Coronal post-contrast T1-weighted image displays inhomogeneous enhancement of the tumor with tortuous vessel (arrows).

Figure 2

A 27-year-old man with alveolar soft part sarcoma. (a) Coronal T1-weighted image shows an isointense signal tumor in the left thigh muscle with an ill-defined border in a 27-year-old man. There are intra- and extratumoral tubular flow voids (arrows). (b) Coronal T2-weighted image reveals the hyperintense signal tumor with signal voids (arrows). (c) Coronal fat-suppressed T2-weighted image displays the hyperintense signal tumor with peritumoral edema. (d) Coronal fat-suppressed post-contrast T1-weighted image demonstrates intense inhomogeneous enhancement of the tumor. (e) Magnetic resonance angiography obtained from dynamic gadolinium-enhanced imaging study shows tortuous, dilated vessels in and around the tumor. (f) A photomicrograph shows oval to polygonal cells with eosinophilic cytoplasm and a nest-like pattern of arrangement (Hematoxylin and eosin, ×20).