Cartilage-forming tumours of bone and soft tissue and their differential diagnosis

The prevalence of primary malignant bone tumours is estimated to be 1:100,000 within the general population: 17–24% of these are malignant cartilaginous tumours (chondrosarcomas). The incidence of benign bone tumours is largely unknown, due to lack of registration as well as frequent failure to present clinically. Benign cartilaginous tumours of bone include chondroma, osteochondroma, chondroblastoma and chondromyxoid fibroma, whereas among the malignant cartilaginous bone tumours conventional, juxtacortical, mesenchymal, dedifferentiated, and clear cell chondrosarcomas are recognized. The histological distinction between the different entities is based on cell type/differentiation, matrix formation and architecture, combined with radiodiagnostic and clinical data. Extraskeletal cartilaginous lesions are extremely uncommon and include soft tissue chondroma, mesenchymal and extraskeletal myxoid chondrosarcoma. The formation of cartilaginous matrix can be found in many other non-cartilaginous tumours (such as periosteal osteosarcoma and chondroblastic osteosarcoma) and tumour-like lesions (such as fibrous dysplasia, Nora's lesion, primary synovial chondromatosis, dysplasia epiphysealis hemimelica and callus formation) These conditions may lead to an erroneous diagnosis of a primary osseous cartilaginous tumour.     

A rare case of periosteal osteoblastoma located in the frontal cranial bone

Periosteal osteoblastoma is an extremely rare bone-forming neoplasm located on the surface of cortical bone. Of the fewer than 30 cases of periosteal osteoblastomas found in the literature, 2 have been reported to be located in cranial bone, and these have not been documented in detail with clinical history, radiographic findings, macroscopic features, and microscopic findings. Although the differential diagnoses of periosteal lesions include parosteal and periosteal osteosarcoma, periosteal chondroma and chondrosarcoma, osteochondroma, osteoid osteoma, periostitis ossificans, and myositis ossificans, an important differential diagnosis both radiologically and pathologically of such a lesion in the cranium is meningioma. We report an unusual case of periosteal osteoblastoma located in the frontal cranial bone that was radiologically consistent with a meningioma. The differential diagnosis of metaplastic meningioma with differentiation toward bone is discussed.     

Primary Osteosarcoma of the Ovary

A case of primary osteosarcoma arising in the left ovary of a 75 year-old female is described. The chief complaint was a sensation of lower abdominal mass. An abdominal plain film showed a large calcified mass in pelvic region, and a preoperative diagnosis of "ovarian fibroma" was made. The excised tumor was divided into 4 pieces, resembling an oyster shell. Microscopically, the tumor fragments were composed of compact bone or woven bone with surrounding atypical osteoblasts and osteoclasts. The tumor was partly composed of numerous spindle cells with malignant osteoid or atypical chondroid formation, and diagnosed as "osteosarcoma". The cystic part of the lesion was lined with a single layer of columnar cells, but the tumor contained no other germ elements or stem cells, or malignant epithelium. Therefore, it is doubtful that this tumor originated from teratoma or malignant mixed mesodermal tumor, and we conclude that this ovarian osteosarcoma arose through a neoplastic change in ovarian stromal cells. The patient died 4 months after surgery due to intra-abdominal and intrathoracic dissemination of the tumor.     

Primary osteosarcoma of the ovary. A case report.

A case of primary osteosarcoma arising in the left ovary of a 75-year-old female is described. The chief complaint was a sensation of lower abdominal mass. An abdominal plain film showed a large calcified mass in pelvic region, and a preoperative diagnosis of "ovarian fibroma" was made. The excised tumor was divided into 4 pieces, resembling an oyster shell. Microscopically, the tumor fragments were composed of compact bone or woven bone with surrounding atypical osteoblasts and osteoclasts. The tumor was partly composed of numerous spindle cells with malignant osteoid or atypical chondroid formation, and diagnosed as "osteosarcoma". The cystic part of the lesion was lined with a single layer of columnar cells, but the tumor contained no other germ elements or stem cells, or malignant epithelium. Therefore, it is doubtful that this tumor originated from teratoma or malignant mixed mesodermal tumor, and we conclude that this ovarian osteosarcoma arose through a neoplastic change in ovarian stromal cells. The patient died 4 months after surgery due to intra-abdominal and intrathoracic dissemination of the tumor.     

Parosteal osteosarcoma of the scapula

Parosteal osteosarcoma is a low-grade osteosarcoma, which occurs on the surface of the bone. We had experienced a parosteal osteosarcoma involving the flat bone, the scapula of a 21-year-old man. This is an extremely rare location for a parosteal osteosarcoma. Plain radiograph showed broad-based, well-defined radiodense lesion at the scapula. Computed tomogram demonstrated an intact cortex and absence of a medullary involvement. Tumor showed a lobulated, high-density lesion, indicating bone formation. Histologically, parosteal osteosarcoma is a well-differentiated osteosarcoma. The tumor is composed of a hypocellular proliferation of spindle cells, with minimal cytologic atypia. The bone is in the form of a well-formed bony trabeculae. Occasional cartilage is present in the form of a cap.     

Fatal pulmonary tumor embolism caused by chondroblastic osteosarcoma: report of a case and review of the literature

Fatal pulmonary tumor embolism is an unusual phenomenon that has only rarely been reported with osteosarcoma. It usually presents with typical symptoms and signs of pulmonary thromboembolism. The authors report the case of a 65-year-old woman with chondroblastic osteosarcoma of the distal femur who suffered a fatal tumor embolism 30 hours after surgery and review the literature.     

Pseudosarcoma in Paget's disease of bone

The appearance of a sarcoma of bone is a well-recognized complication of Paget's disease. The most common type of such a sarcoma is osteosarcoma. Much less common are soft tissue lesions adjoining the pagetic bone that clinically and radiologically simulate sarcoma but histologically represent exaggerated periosteal bone formation as a manifestation of the basic pathologic process. We present a case of a bulky juxtacortical soft tissue mass in the thigh arising from a pagetic femur in a 62-year-old patient with polyostotic Paget's disease that was clinically and radiologically suspected to be a juxtacortical osteosarcoma. Microscopically, the lesion showed features of florid Paget's disease without any evidence of sarcomatous growth. It is important to be aware of this rare manifestation of Paget's disease to avoid unnecessary overtreatment.     

Reactive bone lesions mimicking neoplasms

Reactive lesions of bone and soft tissue can appear alarming on histologic examination because they are often cellular and have atypical (activated) cytologic features, such as distinct nucleoli and mild hyperchromasia, and mitotic activity. Reactive lesions of bone and periosteum also produce bone and cartilage matrix, resulting in confusion with osteosarcoma or chondrosarcoma. Careful attention to key cytomorphological features such as the pattern of bone formation, uniform appearance of cells, and absence of atypical mitoses should help identify the reactive nature of a lesion. Correlation with clinical and radiological findings is also imperative to avoid misclassification of the tumor because reactive lesions often arise at sites where osteosarcoma and chondrosarcoma are rare (e.g., the hand) and lack aggressive radiological features. In this review we discuss reactive lesions of bone that are commonly confused with malignant neoplasms and that the practicing pathologist is likely to encounter at some point. Several of these lesions have had characteristic chromosomal translocations documented in recent years, but continue to be included as reactive lesions based on their overall clinicopathological features.     

Primary osseous rhabdomyosarcoma with focal matrix formation mimicking osteosarcoma

We present an unusual case of primary osseous pleomorphic rhabdomyosarcoma with focal matrix formation mimicking osteosarcoma. The patient was a 21-year-old man who had suffered from pain and slight enlargement of his left calf for 2 months. A plain radiograph demonstrated a large, predominantly osteolytic mass in the region of the proximal fibula with features typical of malignant primary bone tumor. On open surgical biopsy, the tumor consisted of atypical cells, some of them presenting spindle morphology. Between them, there were bands of densely hyalinized matrix with osteoid appearance, but without definite lacunae or calcifications, and an osteosarcoma was diagnosed. Consequently, the tumor was removed. The postoperative tissue presented more pleomorphic cells with some definite rhabdomyoblasts. Desmin, actin, Myf4, and MyoD1 were positive in tumor cells, and a diagnosis of rhabdomyosarcoma was eventually made. Only few cases of primary pure bone rhabdomyosarcoma have been reported. Other bone tumors with rhabdomyosarcomatous differentiation have been described: dedifferentiated chondrosarcoma, fibrosarcoma, and osteosarcoma. Our case does not meet the criteria for sclerosing rhabdomyosarcoma, as matrix formation is focal and cells are spindle-shaped and pleomorphic. However, it is a further example of a diagnostic error in connection with primary osseous tumor.     

Soft tissue osteochondroma: case report and immunohistochemistry for parathyroid hormone-related protein

Surface lesions of bone usually present little diagnostic dilemma because the majority are conventional osteochondromas. Other surface bone lesions include periosteal chondroma, periosteal chondrosarcoma, and parosteal osteosarcoma. Mineralized soft tissue lesions such as myositis ossificans, synovial chondroma, and synovial sarcoma may present in a similar fashion when they occur in a juxtaarticular position. The soft tissue osteochondroma or paraarticular osteochondroma may simulate some of these more aggressive tumors, and its recognition is important to avoid overtreatment. A case of an 11-year-old male with a soft tissue osteochondroma is reported to illustrate the characteristic radiographic and histological features of this rare entity. No prior reports have examined soft tissue osteochondroma for expression of parathyroid hormone related protein, an established cartilage tumor proliferative mitogen.     

Fine-needle aspiration of chondroblastic osteosarcoma of the skull: Report of a case in an 11-year-old girl

We describe an unusual case of chondroblastic osteosarcoma of the skull in an 11-yr-old girl in whom a preoperative diagnosis was made by fine-needle aspiration (FNA) biopsy, followed by histologic confirmation of tissue biopsy and the surgically resected specimen. FNA cytology revealed pleomorphic oval cells with prominent nucleoli along with spindle cells, tumor giant cells, and a chondromyxoid background. The cell block of the aspirated material showed osteoid associated with the malignant cells. Immunocytochemical stains revealed S-100 and vimentin positivity; actin, myoglobin, and cytokeratin stains were negative. Electron microscopy revealed neoplastic cells with chondrocytic differentiation. This case demonstrates the value of FNA biopsy combined with immunocytochemical and ultrastructural studies performed on the aspirated material in diagnosing osteosarcoma from an unusual location such as the base of the skull. Diagn Cytopathol 1996;14:51–55. © 1996 Wiley-Liss, Inc.     

Chondromyxoid fibroma of the femur: a case report with intra-cortical location.

Chondromyxoid fibroma (CMF) is the least common benign cartilaginous tumor, comprising less than 0.5 to 1% of all skeletal neoplasms. This subject was a 16-year-old female with a three-year history of pain involving the distal femoral metaphysis. This case showed an unusual feature: it was intracortical in location. Radiologic differential diagnosis included metaphyseal fibrous defect, periosteal chondroma, simple or aneurysmal bone cyst, and cortical abscess. On operation, the lesion filled the intracortical defect with whitish myxoid soft tissue, bulging into the adjacent soft tissue. Microscopically, it showed typical features of chondromyxoid fibroma composed of mainly myxoid nodules and peripheral fibrous elements with focal chondroid differentiation.     

Extraskeletal osteosarcoma histologically mimicking parosteal osteosarcoma

An extraskeletal osteosarcoma histologically mimicking parosteal osteosarcoma arising in a 63-year-old female is described. The intramuscular lesion in the left lower thigh was a 7 x 4 cm, well-defined mass with marked central calcification and ossification. The tumor was composed predominately of a centrally located osteocartilaginous component and a peripheral, non-osseous fibrous component. The former was characterized by a complex interanastomosing pattern of woven-bone trabeculae with small osteocytes and a minor cartilaginous element. The intratrabecular stroma consisted of benign-appearing fibroblasts. The peripheral fibrous part was characterized by fascicular and interlacing proliferations of spindle cells with mild atypia, rare mitosis and low to moderate cellularity. There were a few scattered foci of proliferating pleomorphic cells, constituting 5% of the tumor, indicating high-grade transformation. There was no evidence of zoning phenomena, cortical erosion, periosteal reaction or intramedullary involvement. The patient is well without recurrence or metastasis at 12 months follow up. This soft tissue neoplasm, mimicking parosteal osteosarcoma, should be distinguished from other bone-forming tumors or tumor-like lesions with which they may be confused. Pathologists and physicians should know the existence of this type of extraskeletal osteosarcoma and treat it as a high-grade extraskeletal osteosarcoma.     

A case of aggressive multiple myeloma with cleaved, multilobated, and monocytoid nuclei, and no serum monoclonal gammopathy

Multiple myeloma is a B-cell malignancy characterized by proliferation of neoplastic plasma cells. A few cases have been reported identifying variant forms of neoplastic plasma cells with atypical nuclei that secrete myeloma protein. We report a highly unusual case of plasma cell myeloma that presented with cleaved, multilobated, and monocytoid nuclei, without detectable myeloma protein in the serum or urine. The bone marrow contained sheets of plasma cells exhibiting pleomorphic nuclei with cleaved, multilobated, and monocytoid features that were negative for myeloperoxidase and dual esterase. Flow cytometric analysis revealed CD38high/CD45low cells expressing cytoplasmic kappa light chain, without evidence of myeloid or lymphoid differentiation. Following chemotherapy, the patient developed secondary plasma cell leukemia. A high plasma cell labeling index was obtained from bone marrow and peripheral blood, indicating a poor prognosis. In addition to quantitative immunoglobulins, serum protein electrophoresis, and immunofixation electrophoresis of serum and urine, we recommend cytochemical and flow cytometric studies for evaluation of suspected plasma cell myeloma with atypical cellular features.     

Fibro-osseous pseudotumor of the digits arising in the subungual region: A rare benign lesion simulating extraskeletal osteosarcoma

A rare case of subungual fibro-osseous pseudotumor of the digits in a 59 year old woman is reported. A painful polypoid mass with ulcerative changes was noted in the subungual portion of the right first toe. Macroscopically, the tumor arose chiefly in the subcutaneous region and was unrelated to the underlying bone tissue. Histologically, the lesion contained fibroblast-like tumor cells producing an extensive osteoid substance in a granulation-like background. Although it was necessary to distinguish the lesion from extraskeletal osteosarcoma, the tumor cells lacked prominent atypical features. It is considered that pathologists and clinicians should add fibro-osseous pseudotumor of the digits to the differential diagnosis of subungual tumor.     

Primary osteosarcoma of the breast

Presented herein is a case of primary pure osteosarcoma of the breast. A 59-year-old woman noticed a left breast tumor. Mammography showed a cluster of crushed stone-like calcifications, which gave the tumor a raw cotton-like appearance. Malignancy was suspected on fine-needle aspiration cytology of the tumor. An excisional biopsy was performed. The tumor was 2.0 × 2.4 cm in size. Histopathologically the tumor was composed of diffuse atypical cells with mitosis and a lot of bone. Atypical cells were thought to be neoplastic osteoblasts. Multinucleated osteoclastic cells were interspersed with osteoblasts. Spindle cells were found at the verge of the tumor. A few entrapped tubular structures were seen. Immunohistochemistry indicated that neoplastic osteoblastic cells of the tumor were stained positively for vimentin, but negatively for epithelial markers; which suggested that the tumor cell elements originated from epithelial cells. This tumor was diagnosed as primary extraskeletal osteosarcoma. Partial resection was additionally performed around the excisional biopsy without dissection of the axillary lymph nodes. Bone radionuclide scan after operation showed no abnormal uptake. At 5 years after surgery no recurrence was seen.     

Extraskeletal osteosarcoma of abdominal wall in a child

Compared with osteosarcoma of bone, extraskeletal osteosarcoma is rare and accounts for approximately 1% to 2 % of all soft tissue sarcomas. Osteosarcoma arising in soft tissues is exceedingly rare in children. The tumor most often affects older adults, involves the lower extremity, responds poorly to chemotherapy, and carries a grave prognosis. The authors describe a 4-year-old girl with an extraskeletal osteosarcoma in the lateral abdominal wall.     

Postirradiation osteosarcoma of the mandible with heterologous differentiation

Heterologous differentiation in osteosarcoma is rare, with only 17 cases previously described in the literature. We report a case of a mandibular osteoblastic osteosarcoma with rhabdomyosarcomatous differentiation in a 45-year-old man who had a history of Hodgkin lymphoma that was treated with chemotherapy and radiation. Radiographs showed a destructive osteoblastic tumor of the mandible that was proven by biopsy to be osteosarcoma. After the patient underwent neoadjuvant chemotherapy, the tumor was resected. It contained a high-grade osteosarcoma composed of osteoblastic and chondroblastic elements that had no definitive response to therapy. Within the center of the lesion was a discrete focus of pleomorphic cells with rhabdomyosarcomatous differentiation that was confirmed by immunohistochemical stains for desmin, myogenin, and myogenic differentiation antigen 1. The patient received additional chemotherapy and radiation therapy but developed lung, brain, and spinal metastases and died 7 months after surgery. To our knowledge, this is the first report of osteosarcoma of the mandible with heterologous differentiation.     

Telangiectatic osteosarcoma--a case report

Telangiectatic osteosarcoma is a rare and special variant of osteogenic sarcoma with distinct radiologic, gross and microscopic features. This tumor is predominantly lytic, destructive tumor without sclerosis on roentgenogram, and is soft and cystic on gross examination. Histologically aneurysmally dilated spaces lined or traversed by stromal cells producing osteoid are noted. This report concerns a case of telangiectatic osteosarcoma occurring in a 7 years old boy. He presented with pathologic fracture of the right distal tibia, followed by a purely lytic lesion on X-ray examination. This lesion recurred five times during a span of one year. Microscopic features of the biopsy specimen was difficult to differentiate from aneurysmal bone cyst because of prominant blood-filled cyst formation. It was finally identified as osteosarcoma from the below-knee amputation specimen through the close examination for anaplastic osteoid-producing stromal cells in the septa that separate the blood cysts.