Background. Frequency distribution data for primary bone sarcomas have long been used to provide clues to the diagnosis of bone cancers after their identification in radiographs. Age and skeletal site are often helpful, in addition to specific radiographic features, in narrowing down the probable histologic categories of bone neoplasms before biopsy. Methods. Data on 2627 histologically confirmed primary malignant tumors of bone, as collected by the SEER program during the period 1973‐1987, were analyzed by age, sex, race, and anatomical site. Results. Osteosarcoma was the most frequently diagnosed primary sarcoma of bone (35.1%), followed by chondrosarcoma (25.8%), Ewing's sarcoma (16.0%), chordoma (8.4%), and malignant fibrous histiocytoma, including fibrosarcoma (5.6%). The most frequently diagnosed sarcoma of bone in persons younger than age 20 was osteosarcoma, followed by Ewing's sarcoma. Chondrosarcoma was the most frequently diagnosed bone tumor in the population older than age 50. The overall 5‐year relative survival rates were as follows: osteosarcoma, 41.0%; chondrosarcoma, 72.7%; Ewing's sarcoma, 41.2%; chordoma, 63.8%; and malignant fibrous histiocytoma, 42.9%. There was an improvement in the survival rates during the period 1973‐1987 for patients with chordoma and for white female patients with Ewing's sarcoma. Ewing's sarcoma and chordoma occurred almost exclusively in the white population. Conclusions. SEER data provide a unique opportunity to evaluate the incidence and survival rates of bone sarcomas, which are uncommon but highly lethal tumors. The findings from this analysis provide information useful in the diagnosis of these cancers.

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Mesenchymal chondrosarcoma presents multiple challenges. Diagnostic pitfalls include inadequate biopsy samples, which may result in sample error. Sox9 has been proposed as a unique marker for mesenchymal chondrosarcoma which may improve diagnostic specificity. Treatment and prognosis vary considerably. Patients who receive surgery and chemotherapy seem to fare better. Multicenter studies with higher sample numbers may improve our understanding of this malignancy.

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Both primary and secondary bone tumours are rare in cats. Of the twenty‐four cases of primary bone tumour, benign or malignant, in the cats of our study, the most common tumour was osteosarcoma (fifteen cats). The osteosarcomas tended to occur in aged female domestic short‐hair cats; nine of the fifteen originated in the long bones of the extremities and three involved the skull. Four juxtacortical osteosarcomas, three chondro‐sarcomas, and one example each of oesteoma and osteoid osteoma were found. The four juxtacortical osteosarcomas developed in relation to cranial bones, a location not recorded previously in cats. Of the five tumour‐like lesions of bone simulating primary tumours, three were aneurysmal bone cysts and two were fibrous dysplasias. Of the twenty‐nine cats with soft tissue tumours or tumour‐like lesions involving bone, eleven had fibrosarcoma, eight had squamous cell carcinoma, three had lymphosarcoma, two had rhabdomyosarcoma, and one example of each was malignant melanoma, haemangiosarcoma, reticulum‐cell sarcoma, meningioma and myositis ossificans. Osteoid osteoma, fibrous dysplasia and myositis ossificans were not previously recorded in the cat.

A review of the clinical, radiologic, and histologic features of 25 cases of long bone adamantinoma is presented. To answer some questions concerning the nature of these tumors, relevant tissue markers were analyzed in seven cases using immunohistochemical assays. This study confirmed the epithelial nature of long bone adamantinomas irrespective of their wide-ranging morphologic patterns that can mimic tumors of various origin. On the basis of distinct radiologic, histologic, and immunohistochemical patterns, a new type of adamantinoma termed "differentiated adamantinoma" could be distinguished from the classic long bone adamantinomas. The diagnostic features characteristic of the differentiated adamantinoma include: patient age (first two decades), intracortical location of the entire lesion, uniform predominance of an osteofibrous dysplasia-like pattern, and scattered positivity of epithelial elements for cytokeratin. We postulate that the predominance of an osteofibrous dysplasia-like pattern in differentiated adamantinoma is the result of a secondary reparative process overgrowing matured and regressing tumor tissue. It is possible that this process may lead to the total elimination of recognizable tumor cells from the lesion. Therefore, osteofibrous dysplasia (ossifying fibroma) of long bones, which has a similar anatomic location, age distribution, and radiologic appearance as differentiated adamantinoma, may, in some cases, represent the evolution of an underlying adamantinoma. Our analysis suggests that long bone adamantinoma could be another member of the unique family of tumors that may regress spontaneously.

Ewing's sarcoma, a highly malignant neoplasm, is characterized by an 11;22 translocation [t(11;22) (q24;q12)], resulting in the fusion of genes FLII and EWS. Adamantinoma of extragnathic bones, a low-grade malignant neoplasm with epithelial features, is not typically considered in the differential diagnosis of Ewing's sarcoma. In this study, three osseous Ewing's sarcomas with histological, immunohistochemical, or ultrastructural epithelial features were subjected to reverse transcription-polymerase chain reaction and sequencing studies for the Ewing's sarcoma molecular rearrangement. (Two of the three cases were originally described as adamantinomas or nontypical Ewing's sarcoma before the availability of genetic characterization.) In addition, traditional cytogenetic analysis and a unique combined interphase molecular cytogenetic/ immunocytochemical approach with bicolor 11;22 translocation breakpoint flanking probes (cosmids) and pancytokeratin antibodies were performed on one neoplasm. At(11;22) (q24;q12) was found in one neoplasm and a type II EWS/FLI-1 fusion transcript was detected in all three neoplasms. The combined genetic/immunocytochemical approach revealed the presence of the 11 ;22 translocation in the nuclei of cytokeratin immunoreactive cells. These genotypic and phenotypic findings delineate a novel Ewing's sarcoma histologic variant, "adamantinoma-like Ewing's sarcoma."