PMC7133003_01
X-ray of the forearm showing a soft tissue tumor with areas of calcification (arrows)
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Fig1
An X-ray of the forearm showed a soft tissue mass with irregular calcifications (Fig. 1) and CT scan of the limb confirmed this finding.
Magnetic Resonance Imaging (MRI) showing a soft tissue mass in the subcutis. The lesion is isointense to muscle in T1-weighted sequence (a), hyperintense on T2-weighted sequence (b), and shows contrast medium enhancement on T1-weighted sequence (c)
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Fig2
The mass was isointense to muscle in T1-weighted sequence (Fig. 2a), hyperintense on T2-weighted sequence (Fig. 2b), with contrast medium enhancement on T1-weighted sequence (Fig. 2c) and highly vascular (Fig. 3).
Low power view showing the two abruptly separated components of the tumor. Well-differentiated leiomyosarcoma is shown in the lower and high-grade osteosarcoma in the upper right (40x)
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Fig4
Histologically, the tumor showed two different, abruptly separated components (Fig. 4).
Well-differentiated leiomyosarcoma consisting of spindle cells arranged in intersecting fascicles (200x)
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Fig5
One consisted of a proliferation of atypical spindle or ovoid cells with cigar-shaped nuclei and eosinophilic cytoplasm arranged in long interlacing fascicles, an appearance consistent with leiomyosarcoma (Fig. 5).
High-grade osteosarcoma consisting of highly atypical cells with osteoid matrix production (a; 200x). In other areas neoplastic cells produced cartilage matrix (b; 100x)
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Fig6
The other component consisted of atypical pleomorphic cells producing osteoid matrix in disorganized trabeculae with focal calcification (Fig. 6).
The leiomyosarcoma component (on the right in a and b) is positive for alpha smooth muscle actin (a, 40x; inset 400x) and desmin (b, 100x), whereas the osteosarcoma component (on the left in a and b) is negative. SATB2 was positive in the nuclei of neoplastic cells in the osteosarcoma component (c, 400x) and negative in the leiomyosarcoma (d, 400x)
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Fig7
Immunohistochemically, areas with leiomyosarcomatous appearance were strongly positive for alpha smooth muscle actin (Fig. 7a) and desmin (Fig. 7b), whereas the osteosarcomatous component was negative. S100 protein, CD34 and CD31. SATB2, a marker of osteoblastic differentiation was positive only in the osteosarcomatous component, whereas leiomyosarcoma areas were negative (Fig. 7c, d).