PMC10288404_01
(a) X-ray of the left-sided chest wall in anterior-posterior plane. (b) CT scan of the chest wall in axial, coronal, and sagittal view. (c) MRI of the chest wall in axial (T2, T1 fs with gadolinium) and coronal (T2 and T1 fs with gadolinium) view.
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External X-ray diagnostics showed a pathological fracture of the eighth left lateral rib with an unclear osteolysis (Figure 1(a)). The CT scan of the ribs showed an expansive, osteolytic intraosseous lesion, 3 x 2 cm in size, with a sclerotic rim and accompanying pathological fracture of the eighth rib on the left lateral side (Figure 1(b)). Similarly, the MRI of the thorax demonstrated evidence of a contrast medium-enhancing lesion without a significant surrounding reaction (Figure 1(c)).
(a)-(d): spindle cell proliferation with multinodular growth pattern an alternating hypercellular and hypocellular areas. Mild nuclear atypia. Focal bone formation. (e): immune reactivity for sm-actin, negative for desmin.
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The samples obtained again showed an indicated biphasic neoplasia consisting of fascicular or cell-rich areas next to cell-poor, increasingly hyalinized, or chondroid-appearing areas without higher-grade cellular atypia, which was differentiated myofibroma-like from the histological aspect (Figure 2(a)-(d)). The remaining immunohistological tests (antibodies against beta-catenin, CD34, desmin, S100, STAT6) were negative again (Figure 2(e)). This variant was classified as probably activating in vitro (Figure 2(e)) so that in the absence of other tumors, the diagnosis of a solitary intraosseous myofibroma was finally made activating PDGFRB mutations represent a characteristic molecular alteration in these lesions.