Osteocalcin and osteonectin immunoreactivity in the diagnosis of osteosarcoma.

Osteosarcomas (OSAs) can be difficult to distinguish histologically from tumors with significantly different biologic potentials and treatment protocols. The correct diagnosis of OSA relies on identification of malignant osteoblasts that are capable of producing neoplastic bone. To determine the use of immunohistochemistry for the diagnosis of OSA, 106 tumors from the Massachusetts General Hospital and the University of Vermont were immunostained with monoclonal antiosteocalcin (OC) and antiosteonectin (ON) antibodies. They included 42 OSAs, 25 non-bone-forming sarcomas, 24 other malignant tumors including lymphomas, carcinomas, and melanomas, and 15 benign bone tumors. Cytoplasmic staining with OC showed 70% sensitivity and 100% specificity, while staining with ON showed 90% sensitivity and 54% specificity for bone-forming tumors, consistently staining cell types other than osteoblasts. Of the OSAs, 83% demonstrated matrix staining with one or both antibodies, whereas dense collagen was negative for both antibodies in all tumors. We conclude that tumor cell cytoplasmic staining with monoclonal OC may be helpful in distinguishing OSAs from other malignancies, and staining of extracellular matrix for OC and ON antibodies concurrently may help distinguish bone matrix from dense collagen.

Retroperitoneal malignant meningioma. A light microscopic, immunohistochemical, and ultrastructural study.

Malignant meningiomas are uncommon and rarely occur outside the central nervous system. We describe herein a morphologically unusual malignant neoplasm that arose in the retroperitoneum of a 25-year-old woman. The tumor was composed of sheets of epithelioid cells that were frequently arranged in prominent whorls. By electron microscopy, the neoplastic cells had long, tapering cell processes that formed numerous interdigitations; many junctions including desmosomes; and abundant intermediate filaments. Immunohistochemistry showed that the tumor cells expressed vimentin, keratin, and epithelial membrane antigen. Based on these findings, the neoplasm was classified as a malignant meningioma. According to our review of the literature, this is the first reported occurrence of a primary retroperitoneal meningothelial neoplasm and the second reported case of an ectopic meningioma that was malignant.

Late development of a malignant fibrous histiocytoma at the site of a giant cell tumor.

A case of late development of a high grade malignant fibrous histiocytoma at the site of a previously surgically treated giant cell tumor is reported. The patient initially was treated for a benign giant cell tumor of the lateral condyle of the distal femur by curettage, implant of auto and allograft bone, but no radiation. Eighteen years later, he noted progressively increasing pain and disability. Radiographs showed some change, but magnetic resonance imaging clearly disclosed a tumor arising at the site and extending outside the bone. After chemotherapy, the tumor was resected and histologically showed no evidence of a recurrent giant cell tumor, only a high grade malignant fibrous histiocytoma.

Multiple enchondromas associated with spindle-cell hemangioendotheliomas. An overlooked variant of Maffucci's syndrome.

Maffucci's syndrome is classically defined as the association of multiple enchondromas and hemangiomas. Spindle-cell hemangioendothelioma (SCH), a recently described vascular tumor of purported low malignant potential, has both cavernous hemangioma and Kaposi-like features. We report six patients with Maffucci's syndrome in whom all vascular lesions were SCH. The enchondromas involved the small and long tubular bones of the extremities in all of these patients; flat bones were also involved in three patients. The SCH usually arose in the extremities, distal to the knees and elbows. Five of the six patients had multiple and separate nodules of SCH, and in four patients there was recurrent or persistent SCH within 6 months to 4 years after initial removal. One patient also had a vascular tumor in the spleen mainly with features of a low-grade angiosarcoma with separate SCH-like foci. None of the SCH have metastasized within a follow-up period averaging 20 years. Five patients are alive 14 to 31 years after presentation. One patient died from metastatic dedifferentiated chondrosarcoma. The patient with the low-grade splenic angiosarcoma is alive approximately 2 years after diagnosis. Reappraisal of the older literature suggests that some of the vascular tumors occurring in Maffucci's syndrome, previously diagnosed as hemangiomas, may in fact be SCH. The apparent association between Maffucci's syndrome and SCH, the presence of SCH in other congenital syndromes, and the young patient age and multicentric distribution of SCH unassociated with Maffucci's syndrome raise the possibility that SCH may be a manifestation of a congenital mesodermal disorder with a genetic background related to Maffucci's syndrome. Although the behavior of SCH appears to be one of a locally recurrent or persistent multicentric lesion that does not metastasize, the association of SCH-like foci in a low-grade angiosarcoma of the spleen raises the possibility that SCH may rarely be associated with a higher grade lesion. Therefore, SCH, at least in the setting of Maffucci's syndrome, should be carefully monitored.

Giant cell tumor of tendon sheath and pigmented villonodular synovitis: immunophenotype suggests a synovial cell origin.

Giant cell tumor of tendon sheath (GCTS) and pigmented villonodular synovitis (PVNS) are common synovial "tumors." Their immunohistochemical profile, however, has not been well characterized, and uncertainty exists regarding their histogenesis and relationship to fibroma of tendon sheath. In an effort to clarify these uncertainties and to better define the immunohistochemical profile of GCTS/PVNS, we examined formalin fixed tissue from 35 specimens of GCTS, 12 specimens of PVNS, and three cases of reactive synovitis using avidin biotin complex (ABC) and streptavidin immunohistochemical methods. Antibodies to vimentin, CD68, HAM56, cytokeratins, EMA, S100, HMB45, leukocyte common antigen, CD34, desmin, and smooth muscle actin were used in the study. The proliferating mononuclear cells and surface synovial cells in GCTS/PVNS and reactive synovitis stained positively for CD68, HAM56, and vimentin only. Multinucleated cells stained for CD68, vimentin, and leukocyte common antigen. All other stains were negative. Our results suggest that GCTS/PVNS are tumors of synovial cell origin, and do not support an association between GCTS and fibroma of tendon sheath.

Comparison of triphenyltetrazolium dye with light microscopic evaluation in a rabbit model of acute cerebral ischaemia.

The present study was performed to compare brain infarct size assessment by routine histology (haematoxylin and eosin) and by 2,3,5-triphenyltetrazolium chloride staining techniques. New Zealand white rabbits were subjected to autologous clot embolization to the anterior circulation of the brain. After a study period of 7-8 h the brains were harvested and serially sectioned in the coronal plane. Brain slices were then immersed in a 1% triphenyltetrazolium chloride dye. Following visualization of the infarcted region, the brains were immediately placed in 10% formalin and later prepared for histologic evaluation by routine haematoxylin and eosin. The two methods were compared for their ability to estimate infarct size by an independent observer. There was excellent correlation between the two methodologies; infarct sizes of 57.4 +/- 5.0% versus 55.9 +/- 5.4% (mean +/- SEM, p < 0.007, r = 0.73, n = 12; expressed as percentage of the hemisphere infarcted) were noted for light microscopic evaluation versus triphenyltetrazolium chloride staining, respectively. It is concluded that triphenyltetrazolium chloride staining is an acceptable method for delineating brain infarct size in this rabbit model of thromboembolic stroke. The relative ease of infarct size determination with this technique suggests its more widespread use in similar models.