PMC6079448_01
(a) marked swelling and induration of the left distal femur and (b) X-ray shows bone outgrowths (exostoses) on the medial and lateral aspects of the distal femur bilaterally and left metaphyseal widening (AP view).
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The lesion on the left distal femur was markedly enlarged and tender, with induration, reddening, and limited range of motion of his knee joint (Figure 1(a)). Repeat X-rays confirmed the presence of bony outgrowths (exostoses) on the medial and lateral aspects of the distal femurs bilaterally and left metaphyseal widening common in this condition as had been previously identified when he was diagnosed at age 3, and further investigations of the left distal femur swelling (Figure 1(b)) with magnetic resonance imaging (MRI) revealed a distinct enhancing lesion in the distal aspect of the left thigh at the site of intense swelling and pain.
MRI with (a) coronal T2W1 demonstrates heterogeneous signal intensity, (b) coronal T1W1 with contrast, and (c) axial T1W1 with contrast demonstrates moderate heterogeneous enhancement. There were no skip lesions.
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MRI showed a lesion with hypointense signals on T1WI sequences and has heterogeneous signal intensities with moderate and heterogeneous enhancement on T1WI postcontrast study and on T2WI sequences; the lesion had heterogeneous signal intensities (Figures 2(a)-2(c)).
Photograph showing the (a) exostosis and (b) after excision of the exostosis of the left distal femur (see thick blue arrows).
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At surgery, there was a necrotic lesion, and excision biopsy at the site of the left distal femur exostosis was taken (Figures 3(a) and 3(b)).
Photomicrographs showing (a) fibrocartilaginous cap (osteochondroma or exostosis-green arrow) (H&E x20), (b) the tumor-forming osteoid in the marrow and numerous pleomorphic bizarre osteoblasts (H&E x100), and (c) higher power showing spicules of new bone (osteoid) (blue arrow) among the osteoblasts (red arrow) (H&E x400).
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In conclusion, histopathological revealed an osteochondroma with an underlying high-grade osteoblastic osteosarcoma involving the marrow cavity (Figures 4(a)-4(c)).
CT scan showing (a) axial section of the chest and pelvis cavity, no metastases detected, and (b) abdomen and chest are normal.
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For staging purposes, CT scans of the chest, abdomen, and pelvis were done to investigate any presence of metastatic lesions (Figures 5(a) and 5(b)).