Desmoplastic small round cell tumor of the pleura.

Three cases of desmoplastic small round cell tumor (DSRCT) with multiphenotypic differentiation, primary in the pleura, are presented. This is a previously unrecognized site for this tumor type. Two patients were male and one female aged 29, 24, and 17 years. All presented with chest pain and were found to have pleural-based tumors associated with pleural effusion. Abdominal involvement was not present in any of the cases. Histologically, the tumor showed the characteristic features of intra-abdominal DSRCT, including angulated nests of small cells embedded in a vascular fibroblastic stroma, focal rhabdoid phenotype, and areas of central necrosis. The neoplastic cells showed evidence of epithelial, mesenchymal, and neural differentiation with characteristic dot-like positivity for vimentin and desmin topographically corresponding to perinuclear aggregates of intermediate filaments identified on electron microscopy in one case. Two patients died of disease 2 years and 15 months after presentation, respectively, and one patient is alive with disease 18 months after presentation. The histogenesis of DSRCT is unknown. Most previously reported cases involved the peritoneum or tunica vaginalis, suggesting a histogenetic relationship to the mesothelium. The occurrence of these tumors in the pleura lends further support to this theory.

Ectomesenchymal chondromyxoid tumor of the anterior tongue. Nineteen cases of a new clinicopathologic entity.

We present 19 cases of a previously undescribed myxoid tumor of the anterior tongue. These lesions occurred in nine women and 10 men aged 9 to 78 years (median, 32 years). Most tumors were seen as slow growing, painless nodules in the anterior dorsal tongue. The duration of growth ranged from a few months to 10 years. All tumors were treated by surgical excision, and two recurred. Microscopically, they exhibited a lobular proliferation of ovoid and fusiform cells, which often had multilobated nuclei and occasional foci of atypia, in a chondromyxoid background. Some tumors entrapped muscle or nerve fibers and had a tendency for blunt infiltration of adjacent tissue. The cells were diffusely and intensely immunoreactive for glial fibrillary acidic protein (GFAP) and cytokeratin but were decorated less frequently with antibodies for smooth muscle actin and S-100 protein. Reactivity for epithelial membrane antigen and desmin was not found. We believe these tumors fail to meet established clinicopathologic criteria for any existing myxoid neoplasms of the tongue, including nerve sheath myxoma, myoepithelioma, benign mixed tumor, ossifying fibromyxoid tumor of soft parts, extraskeletal myxoid chondrosarcoma, and glial and chondroid choristomas or heterotopias. Although the histogenesis of this neoplasm is unclear, we suspect that a cell of undifferentiated ectomesenchyme is the progenitor and suggest the descriptive term ectomesenchymal chondromyxoid tumor (ECT) of the anterior tongue be adopted.

Establishment of three rat soft tissue tumor cell lines with different degrees of myogenic differentiation.

Soft tissue malignancies often show divergent differentiation, including myogenic lineage. Five rat tumors induced with 20-hydroxymethylcholanthrene (20-OH-MCA), were cultured in vitro, and three cell lines (YMC-1, YMC-2, YMC-3) were established from them. YMC-2 and -3 cells were spindle-shaped, and YMS-1 cells round and epithelioid. In confluency, YMC-3 cells formed myotubes. The nude mouse xenotransplants showed morphological features consistent with their myogenic phenotypes. Muscle-specific enzyme activities were highest in YMC-3 cells. These lines may be useful in the investigation of the myogenic differentiation of undifferentiated mesenchymal cells.

Small round cell tumor with divergent differentiation: cytologic, histologic, and ultrastructural findings.

A case study of desmoplastic small round cell tumor with divergent differentiation in a 13-yr-old boy is presented. Clinical, cytologic, histologic, immunohistochemical, and ultrastructural findings are reported. There was a close correlation between the various histologic and cytologic patterns. Immunohistochemical studies revealed strong positivity of many of the tumor cells for cytokeratin, vimentin, and desmin. Ultrastructurally, some of the tumor cells contained aggregates of cytoplasmic intermediate filaments. Fine-needle aspiration biopsy may suggest the diagnosis of desmoplastic small round cell tumor. Confirmation of the diagnosis may be provided by immunohistochemistry and electromicroscopy.

Morphogenesis of compound melanosomes in melanoma cells of a gray horse.

A thoroughbred horse, gelding, gray color, aged 19 years old had cutaneous melanomas from the root to the middle of the tail, and throughout the connective tissues of the whole body. Histologically, the tumors were diagnosed as mature melanotic melanomas characteristically deposited with abundant melanin pigment. Examined with an electron microscope, melanosomes were electron opaque without internal structure (stage IV), or as mature granular and lamellar types. Most of them were fused with each other, and formed compound melanosomes, which was similar to internal melanin aggregates in shape. The internal melanin aggregates gradually disintegrated, and compound melanosomes grew spherical. The compound melanosomes changed into autophagosomes.

Intraabdominal desmoplastic small round cell tumor. Report of a case diagnosed by fine needle aspiration cytology.

In this report, fine needle aspiration (FNA) findings in a case of intraabdominal desmoplastic small round cell tumor (IADSRCT) are presented. Computed tomographic scan-guided FNA performed on a right upper abdominal mass on a 20-year-old man produced a cellular specimen consisting of monomorphic small round cells with scant cytoplasm and ovoid nuclei. FNA cytology and immunocytochemistry suggested the diagnosis of IADSRCT. Surgical removal of the tumor and detailed histology and ultrastructural studies confirmed the cytologic findings.

A new type of connective tissue nevus: isolated exophytic elastoma.

An unusual case of isolated exophytic elastic tissue nevi in the scrotal region of a 64-year-old man is described. The histological and ultrastructural findings were those of abundant abnormal elastic fibers and increased reticulin in the dermis. This hamartomatous lesion possesses clinical and histological features previously undescribed in connective tissue nevi.

Soft tissue neoplasma of the mediastinum.

Among all neoplasms of the mediastinum, those composed of mesenchymal elements, and arising primarily in mediastinal soft tissue, are the least common group of tumors discussed in this issue of Seminars. Apart from tumors of nerve sheath, neuroectoderm, adipose tissue, and lymphatic vessels, few of them will comprise a significant part of the surgical pathologist's practice. Yet each poses two important clinical problems: the recognition of visceral-associated (as opposed to primary soft tissue) lesions, and the exclusion of metastases from an extrathoracic site. In this review, the histologic, immunohistochemical, and ultrastructural features that characterize mediastinal soft tissue tumors will be emphasized. Clinical aspects of these lesions are also discussed, particularly as they may relate to the aforementioned clinical questions.

Light and electron microscopic examination of fine-needle aspirates in the preoperative diagnosis of cartilaginous tumors.

Twenty-eight patients with chondrogenic tumours--2 chondroblastomas, 4 chondromas, 18 chondrosarcomas, 1 clear-cell chondrosarcoma, and 3 mesenchymal chondrosarcomas--underwent fine-needle aspiration biopsy (FNAB) in the preoperative investigation. The cytologic features in smears were compared with the histopathologic findings in the surgical specimens; in 14 cases they were also compared with the light and electron microscopic findings in resin-embedded fine-needle aspirates. The smears of the vast majority of the classical chondrosarcomas presented features that made possible the FNAB diagnosis of a chondrogenic tumor to be made. In the case of the low-grade chondrosarcomas in particular, which were poorly or moderately cellular in smears and showed chondroblastic cells often in lacunary structures of hyaline matrix, consideration of the clinical presentation, size, location, and roentgenographic appearance was essential for the diagnosis of chondrosarcoma. On the other hand, the high-grade chondrosarcomas presented cytologic features that clearly indicated their malignancy and they usually had a myxoid matrix. The possible differential diagnoses that may arise from the FNAB diagnosis of cartilaginous tumors are discussed. The resin-embedding technique for the light and electron microscopic examination of FNABs, along with the histochemical analysis for the demonstration of sulphated glucosaminoglycans and the immunocytochemistry applied to smears, was found to be of value in the definite diagnosis, especially in the distinction of chondrogenic tumors from chordoma and metastatic mucous-producing carcinoma.

Histopathology and ultrastructure of tumours and tumour-like lesions of bone.

The monograph summarizes the most important data and experience based on the clinicopathological analysis, histological and histoenzymatic examinations of more than 1000 primary tumours and 400 tumour-like lesions of bones. The diagnosis of them has been based on the WHO classification of bone tumours which appeared to be the best in meeting the needs of diagnostic practice. However, in our collection of cases also occurred such cases which did not fit into the WHO diagnostic scheme. They included lesions the separate existence of which could be proved only recently or has remained the matter of discussion, such as periosteal osteosarcoma, clear-cell and dedifferentiated chondrosarcoma, malignant fibrous histiocytoma, the so-called parachordoma, resorptive giant-cell granuloma, reactive periostitis of tubular bones of hands and feet, and the tibial lesion reminiscent of cementifying fibroma. In the majority of types of the tumours and tumour-like lesions of bones electron microscopical examination was carried out (203 cases), the results of which are presented here in a considerable extent. On the one hand, electron microscopy facilitated the diagnosis in some cases, and, on the other hand, it proved as extremely important in solving the problems of histogenesis of some of the lesions.

Electron microscopy of fine needle aspiration biopsy from soft tissue tumors.

The value of electron microscopy as an adjunct to fine needle aspiration cytology in the preoperative diagnosis of soft tissue tumors was studied in 22 cases. In 19 of these, the aspirated material obtained was adequate for electron microscopy analysis. The aspiration procedure did not damage the cells, and the aspirates were well suited to electron microscopic examination. In many cases this examination enhanced the precision of diagnosis and subclassification. This was the case in two intramuscular myxomas diagnosed as myxoid liposarcomas with light microscopy and in two sarcomalike squamous cell carcinomas diagnosed as polymorphous sarcomas in the ordinary smears.

Extracellular matrix vessels in human osteogenic neoplasms: an ultrastructural and enzymatic study.

The results of a study of the ultrastructural and enzymatic features of extracellular matrix vesicles in human osteogenic neoplasms are reported. Specimens from three osteosarcomas, a chondrosarcoma, and an osteoblastoma were processed for electron microscopic study and for preparation of vesicular, membrane, and cellular fractions. Electron micrographs of each lesion showed primary mineralization comprised of matrix vesicles and calcifying nodules. There was a distinct pattern of distribution of enzymatic activity among fractions from the osteosarcomas; namely that the highest values for specific activity of alkaline and pyrosphosphatases and adenosine triphosphases (ATPases) in the vesicle fractions and lowest in the cell fractions. This pattern was not consistent in fractions from the other neoplasms. The aforementioned enzymes are considered essential for the onset of mineralization. The data presented establish the role of matrix vesicles in neoplastic calcification and suggest the need for further studies into the diagnostic value of the vesicles.

Myofibroblasts in fibrous tumors and fibrosis in various organs.

The morphology and population of myofibroblasts detected by electron microscopy in fibrous tumors and fibrosis in various organs have been examined. The myofibroblast was identified by characteristic features of the indented nucleus, bundles of abundant microfilaments with dense bodies, focal basal lamina and well-developed rough endoplasmic reticulum. It has been observed that myofibroblasts in a variety of fibrous tumors and fibrosis appeared predominantly in fibromatosis and reparative process of deep fibrous tissues and organs particularly in the lesions involving the fascia and subcutaneous tissue. It was suggested that myofibroblasts would be modified fibroblasts to which fibroblasts in the fascia and deeply situated fibrous tissue transformed during proliferation and differentiation.