Low-grade myxofibrosarcoma following a metal implantation in femur: a case report

Abstract

Myxofibrosarcoma is a myxoid variant of malignant fibrous histiocytoma that most commonly involves the extremities of elderly people. However, a primary myxofibrosarcoma with bone invasion in young adults is extremely rare. Herein, we report the case of a 31-year-old male with a gradually enlarging left thigh mass, who had a history of left femur fracture and received an open reduction and internal fixation with titanium alloy plates and screws 33 months previously. Imaging investigations revealed an irregularly shaped soft tissue mass around the left femur shaft and a partial bone defect in the middle one-third of the left femur. Pathological examination of the resected specimen showed a multi-nodular appearance, abundant myxoid matrix and elongated curvilinear capillaries. Immunohistochemical studies revealed that the tumor cells was positive for VIM and MDM2, and was negative for CK, MSA, SMA, DES, S-100 and CD34. Labeling index of Ki-67 was 25%. Based on the morphological finding and immunostaining, it was diagnosed as a low-grade myxofibrosarcoma. The clinical and imaging examinations did not reveal the evidence of a primary cancer elsewhere, and the patient had no personal or family history of malignancy. To our knowledge, this is the first case of a primary myxofibrosarcoma developed following a fracture and metal implantation in young adults.

Virtual slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1745984882113605.

Figure 1

CT images of the left thigh. (a) Transverse image. (b) Coronal image. A high-resolution volumetric CT scanning revealed a 9.7 × 11 × 19 cm irregularly shaped soft tissue mass in the anteromedial left thigh (yellow arrow) and a partial bone defect approximately 9.7 cm in length on the medial border of the left femur shaft (light blue arrow).

Figure 2

Histopathological examination of the tumor. (a) Magnification, ×40. (b) Magnification, ×100. H&E staining showed that the tumor was predominantly composed of a large number of diffuse fusiform cells and myxoid matrix. The fusiform tumor cells were arranged in a multi-nodular pattern, with indistinct cell margins, slightly eosinophilic cytoplasm, and hyperchromatic atypical nuclei. Mitoses were infrequent. Many elongated curvilinear capillaries were observed.

Figure 3

Immunohistochemical studies of the tumor. (a-i) Magnification, ×200. The tumor cells expressed strong immunoreactivity for VIM (a) and negative for CK (b). Labeling index of Ki-67 (c) was 25%. MSA (d), SMA (e), DES (f) and S-100 protein (g) were negative in the tumor cells. (h) CD34 staining was detected in vascular endothelial cells rather than in tumor cells, highlighting the curvilinear capillaries. (i) MDM2 was positive in the tumor cells.

Figure 4

MRI images of the thigh. (a) Transverse T2-weighted image. (b) Coronal T1-weighted image. MRI images showed an irregular soft tissue mass with ill-defined margin in the anteromedial left thigh (yellow arrow), accompanied by surrounding soft tissue swelling and normal muscle structure disappearance. Bone destruction in the left femur shaft was observed (light blue arrow).

Figure 5

Histopathological examination of the recurrent tumor. (a) Magnification, ×200. (b) Magnification, ×400. H&E staining showed that the tumor cells exhibited increased atypia and pleomorphism compared with those in the primary tumor, varying from small and bland to enlarged, bizarre, pleomorphic and multinucleated. Abundant myxoid matrix and elongated curvilinear capillaries were also observed.