Primary bone carcinosarcoma of the fibula with chondrosarcoma and squamous cell carcinoma components

Abstract

Carcinosarcoma is defined as a malignant neoplasm that is composed of both carcinomatous and sarcomatous components. The occurrence of carcinosarcoma in the bone is extremely rare. In this report, we describe the third documented de novo case of carcinosarcoma of the bone. A 59-year-old Japanese female presented with a painful tumor in her right lower leg. Plane radiography revealed an osteolytic destructive lesion with periosteal reaction and mineralization in the right fibula. Resection of the fibula tumor was performed under a clinical diagnosis of chondrosarcoma. Histopathological study revealed that the tumor was comprised of three components. The main component was proliferation of small round to short spindle cells (approximately 50%), and the remaining components were chondrosarcoma (30%) and squamous cell carcinoma (20%). Immunohistochemically, SOX9 was expressed in the small round to spindle cells and chondrosarcoma component, and p63 and p40 were expressed in all three components. Accordingly, an ultimate diagnosis of carcinosarcoma of the bone was made. The clinicopathological analysis of carcinosarcoma of the bone revealed that this type of tumor affects the middle-aged to elderly persons and occurs in the long bone. All three de novo cases had chondrosarcoma and squamous cell carcinoma components. One of the 3 patients died of the disease. The histogenesis of carcinosarcoma of the bone remains a matter of controversy, although a multpotential stem cell theory has been proposed. Additional studies are required to clarify the clinical behavior and histogenesis of carcinosarcoma of the bone.

Keywords: Carcinosarcoma; bone; chondrosarcoma; squamous cell carcinoma.

Figure 1

Plane radiography showing an osteolytic destructive lesion invading into the surrounding soft tissue of the right fibula. Periosteal reaction and slight mineralization are also noted.

Figure 2

Histopathological features of the biopsy specimen of the fibula tumor. A: Proliferation of irregular-shaped lobules of cartilage permeating into the bone trabeculae, HE, x 40. B: The chondrocytes show mild high cellularity and have mildly enlarged nuclei. At the periphery of the cartilage lobules, a trabecular growth of atypical cells is observed, HE, x 200. C: These cells have a high nuclear/cytoplasmic ratio and large round to oval nuclei containing small nucleoli. Small nests of atypical cells with pearl formation are occasionally noted (inset), HE, x 400.

Figure 3

Histopathological features of the surgical specimen of the fibula tumor. A: The tumor is composed of three components: small round to short spindle cells, chondrosarcoma, and squamous cell carcinoma, HE, x 40. B: Small round to short spindle cell component. These cells have round to oval nuclei containing small nucleoli. Nests of squamous cell carcinoma are also observed, HE, x 200. C: Chondrosarcoma component. Obvious lacula and chondroid matrix formation are present. The nuclei of the chondrocytes are large, and binucleated cells are scattered. HE, x 200.

Figure 4

Immunohistochemical features of the fibula tumor. Cytokeratin (AE1/AE3) is expressed only in the squamous cell carcinoma component. p63 is expressed in all three components. Positive immunoreactivity for SOX9 is observed in the small round to spindle cells and chondrosarcoma component. x 40.