Retroperitoneal Sarcoma with Features Suggestive of Alveolar Soft Part Sarcoma

A 72-year-old man presented with a 15 × 12 × 5 cm cystic and necrotic tumor involving the superior region of the stomach and the retroperitoneum down to the transverse colon and extending laterally from the left lobe of the liver to the spleen without involving either organ. Light microscopy showed the tumor cells to be arranged in an organoid pattern. Immunocytochemistry showed a strong reaction for desmin and vimentin. Electron microscopy demonstrated features suggestive of an alveolar soft part sarcoma.     

Extraskeletal Ewing's Sarcoma

A well documented case of extraskeletal Ewing's sarcoma arising in a finger of a 16-year-old man was studied by light microscopy, immunohisto-chemistry and electron microscopy. The differential diagnoses of similar “round cell neoplasms” are discussed. Emphasis is placed on the distinction between extraskeletal Ewing's sarcoma and peripheral neuroepithelioma.     

Retroperitoneal Sarcoma with Features Suggestive of Alveolar Soft Part Sarcoma

A 72-year-old man presented with a 15 × 12 × 5 cm cystic and necrotic tumor involving the superior region of the stomach and the retroperitoneum down to the transverse colon and extending laterally from the left lobe of the liver to the spleen without involving either organ. Light microscopy showed the tumor cells to be arranged in an organoid pattern. Immunocytochemistry showed a strong reaction for desmin and vimentin. Electron microscopy demonstrated features suggestive of an alveolar soft part sarcoma.     

Extraskeletal Ewing's Sarcoma

A well documented case of extraskeletal Ewing's sarcoma arising in a finger of a 16-year-old man was studied by light microscopy, immunohisto-chemistry and electron microscopy. The differential diagnoses of similar “round cell neoplasms” are discussed. Emphasis is placed on the distinction between extraskeletal Ewing's sarcoma and peripheral neuroepithelioma.     

Sarcoma gene signatures

This review reports the main gene signature specific for the diagnosis, prognosis or prediction of drug response in sarcomas. Almost half of sarcomas show a simple genetic lesion which is specific for the diagnosis: recurrent translocations in 10 to 15% of sarcomas, specific activating and inactivating mutations in GIST and rhabdoid tumor respectively, and MDM2 amplification in well-differentiated and dedifferentiated liposarcomas as well as in intimal sarcoma. A recent study reported a gene expression signature which is much better than histological grading for predicting metastasis outcome. This signature is composed of 67 genes all belonging to pathways involved in chromosome integrity suggesting an important role of these mechanisms in the development of metastases. On the other hand, and except for GIST with KIT and PDGFRA mutations, there is no validated predictive gene signature so far.     

Intriguing Case: Primitive Pelvic Sarcoma Resembling Clear Cell Sarcoma of Kidney

Clear cell sarcoma of kidney (CCSK) is an aggressive childhood renal tumor of unknown histogenesis that has not been reported to occur outside the kidney. The article describes an extrarenal neoplasm arising in the pelvic soft tissues of a 13-year-old boy that was composed predominantly of uniform mesenchymal cells with optically clear cytoplasm supported by an arborizing network of small blood vessels, which was indistinguishable in appearance from CCSK. The electron microscopic findings, although nonspecific, were essentially identical to those of CCSK, with tumor cells displaying fine chromatin, electron-lucent cytoplasm, and intercellular collagen but no evidence of tissue-specific differentiation. Immunocytochemical studies showed positivity for vimentin but negative results for desmin, myoglobin, cytokeratin, epithelial membrane antigen, S-100 protein, neuron-specific enolase and factor VIII-related antigen. Tumor cells were also nonreactive with Ulex lectin. This unusual pelvic tumor and CCSK may both derive from primitive mesenchymal cells and may represent phenotypic but not necessarily histogenetic analogs.     

Ultrastructural Similarities and Differences of Synovial Sarcoma, Epithelioid Sarcoma, and Clear Cell Sarcoma of the Tendons and Aponeuroses

The ultrastructural features of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses were compared to identify differential markers and similarities. A continuous spectrum of modulation of morphologic features of synovial and epithelioid sarcomas was observed. Biphasic synovial sarcoma with pseudoglandular and stromal components represents one extreme of this spectrum. The gradual disappearance of the pseudoglands and the formation of nests of epithelial-like cells, which are characteristic of epithelioid sarcoma, were observed. The cells of clear cell sarcoma, as well as those of synovial and epithelioid sarcomas, form epithelial-like islands; however, the presence of premelanosomes in the former is a feature of neural crest derivatives.     

Ultrastructural Similarities and Differences of Synovial Sarcoma,Epithelioid Sarcoma,and Clear Cell Sarcoma of the Tendons and Aponeuroses

The ultrastructural features of synovial sarcoma, epithelioid sarcoma, and clear cell sarcoma of the tendons and aponeuroses were compared to identify differential markers and similarities. A continuous spectrum of modulation of morphologic features of synovial and epithelioid sarcomas was observed. Biphasic synovial sarcoma with pseudoglandular and stromal components represents one extreme of this spectrum. The gradual disappearance of the pseudoglands and the formation of nests of epithelial-like cells, which are characteristic of epithelioid sarcoma, were observed. The cells of clear cell sarcoma, as well as those of synovial and epithelioid sarcomas, form epithelial-like islands; however, the presence of premelanosomes in the former is a feature of neural crest derivatives.     

Epithelioid Monophasic Synovial Sarcoma

A 47-year-old man presented with a soft tissue mass of the distal right thigh near the knee. The tumor was highly vascular with epithelioid tumor cells growing in a peritheliomatous pattern, suggesting a soft tissue glomus tumor. Yet many tumor cells contained hemosiderin pigment and formed papillary structures suggestive of pigmented villonodular synovitis. Tumor cells were cytologically bland, and there was minimal mitotic activity. The tumor cells were strongly immunoreactive for cytokeratin, however, and contained true desmosomes, gland lumina, microvilli, tonofilaments, and well-developed basal lamina. These findings plus the absence perinuclear aggregates of intermediate filaments rule out malignant rhabdoid tumor and epithelioid sarcoma. Also, magnetic resonance imaging revealed no other lesions to suggest metastatic carcinoma. Thus this tumor appears to be a predominantly epithelioid form of monophasic synovial sarcoma. Recognition of this variant of synovial sarcoma is important for prognostication and therapeutic decision making because some studies indicate that this variant of synovial sarcoma follows a relatively benign clinical course.     

Intriguing Case: Primitive Pelvic Sarcoma Resembling Clear Cell Sarcoma of Kidney

Clear cell sarcoma of kidney (CCSK) is an aggressive childhood renal tumor of unknown histogenesis that has not been reported to occur outside the kidney. The article describes an extrarenal neoplasm arising in the pelvic soft tissues of a 13-year-old boy that was composed predominantly of uniform mesenchymal cells with optically clear cytoplasm supported by an arborizing network of small blood vessels, which was indistinguishable in appearance from CCSK. The electron microscopic findings, although nonspecific, were essentially identical to those of CCSK, with tumor cells displaying fine chromatin, electron-lucent cytoplasm, and intercellular collagen but no evidence of tissue-specific differentiation. Immunocytochemical studies showed positivity for vimentin but negative results for desmin, myoglobin, cytokeratin, epithelial membrane antigen, S-100 protein, neuron-specific enolase and factor VIII-related antigen. Tumor cells were also nonreactive with Ulex lectin. This unusual pelvic tumor and CCSK may both derive from primitive mesenchymal cells and may represent phenotypic but not necessarily histogenetic analogs.     

Kaposi's Sarcoma and Transplantation

Kaposi's sarcoma is a tumour of multicentric origin, composed of endothelium-lined vascular spaces and spindle-shaped cells. The incidence of Kaposi's sarcoma in transplant recipients is 400--500 times greater than that in the general population, and is rising within the transplant population, currently comprising more than 5% of all de novo neoplasms in this group. The exact pathogenesis is still unknown but DNA sequences from human herpesvirus 8 (HHV-8) are present in the different clinical variants of Kaposi's sarcoma. Risk factors associated with development of these tumours posttransplantation include the geographical origin of the patient, HSV-8 infection before and after transplantation, and the immunosuppressive regimen used, but the importance of each factor remains to be determined. Apart from conventional treatment with surgical excision, radiotherapy or chemotherapy, cessation, reduction or modification of immunosuppressive therapy has been shown to be effective in a significant number of patients. This article reviews recent advances in our understanding of Kaposi's sarcoma after transplantation.     

Ultrastructure of Kaposi Sarcoma

Kaposi sarcoma (KS) is a complex disease with aspects of virology (human herpesvirus-8, HHV-8, and human immunodeficiency virus, HIV), immunology (immunodeficiency), hyperplasia (multiple widely spaced de novo lesions), and neoplasia (metastases) that has always been the most common AIDS-defining malignancy. The lesional spindle cell has been classified as being derived from either blood vascular or, more recently, lymphatic endothelial cell origin. This study revealed a spectrum of endothelial cell ultrastructure from lymphatic to blood vascular. It demonstrated frequent Weibel-Palade bodies and gap junctions. The spindle cells were shown to behave as facultative phagocytes, internalizing and processing necrotic cells and leaked red blood cells (RBCs). Fragmented RBCs were equivalent to the “hyaline droplets” seen by light microscopy. The final stages of RBC disintegration were hemosiderin and ferritin. Most significantly, this study disclosed that KS is actually composed of a single type of randomly oriented spindle cell forming vessels of varying size and integrity.     

Synovial Sarcoma with Squamous Metaplasia

We report on a biphasic synovial sarcoma showing slight squamous cell differentiation of their epithelioid component under the light microscope. The electron microscopical examination revealed numerous tono-filaments arranged in dense bundles, which could be characterized as tonofibrils with keratohyalin granules in the same cells. The presence of such structures indicates the possibility of squamous metaplasia in biphasic synovial sarcoma.