Myxoid liposarcoma. An electronmicroscopic study: biological and histogenetic considerations

Pathologic and molecular aspects of soft tissue sarcomas

This article retains the conventional approach to the classification of soft tissue sarcomas, dividing them into several major histogenetic categories based on their overall microscopic appearance, tissue differentiation pattern, and biologic potential. The author advocates a multimodal approach, in which four distinctive data sets--clinical, radiographic, microscopic, and, in some cases, molecular--are considered to establish the diagnosis and treatment plan. Such step-wise analysis is more likely to lead to consistency and accuracy as compared with an intuitive approach based on fragmentary data. The author describes individual lesions of soft tissue as clinicopathologic entities and believes that they can be more accurately diagnosed and appropriately treated with the help of data generated by a multidisciplinary team. In addition, this article emphasizes the need to use emerging molecular techniques that can provide important clues for both diagnosis and prognosis.

The morphologic spectrum of hibernoma: a clinicopathologic study of 170 cases

Hibernoma, an uncommon tumor of brown fat, has been described only in a few case reports and small series. The authors reviewed 170 cases of hibernoma and evaluated the morphologic features and the behavior of this tumor. The records from the Soft Tissue Registry of the Armed Forces Institute of Pathology from 1970 were searched for cases coded as "hibernoma." Clinical information and available slides from 170 hibernomas were reviewed. Immunohistochemical staining for S-100 and CD34 was performed on select cases. Follow-up information was obtained from the patients' medical records, the patients' physicians, and the patients themselves. Of 170 patients with hibernoma, 99 were men and 71 were women. The tumor occurred most commonly in adults, with a mean age of 38.0 years (age range, 2-75 years). Nine tumors occurred in pediatric patients. The most common anatomic locations included the thigh (n = 50), shoulder (n = 20), back (n = 17), neck (n = 16), chest (n = 11), arm (n = 11), and abdominal cavity/retroperitoneum (n = 10). The average duration of the tumor was 30.6 months. Tumor size ranged from 1 to 24 cm with an average dimension of 9.3 cm. All tumors were composed partly or principally of coarsely multivacuolated fat cells with small, central nuclei and no atypia. Four morphologic variants of hibernoma were identified: typical, myxoid, spindle cell, and lipoma-like. "Typical" hibernoma (n = 140) included eosinophilic cell, pale cell, and mixed cell types based on the tinctorial quality of the hibernoma cells. The myxoid variant (n = 14) contained a loose basophilic matrix. Spindle cell hibernoma (n = 4) had features of spindle cell lipoma and hibernoma; all occurred in the neck or scalp. The lipoma-like variant (n = 12) contained only scattered hibernoma cells. Immunohistochemically, 17 of 20 cases (85%) were positive for S-100 protein. Only one hibernoma of 20, a spindle cell variant, was positive for CD34, whereas other hibernoma variants were negative. Follow-up was obtained for 66 cases (39%) over a mean period of 7.7 years (range, 6 months-28 years). None of the patients with follow-up had a recurrence or metastasis, including eight with intramuscular tumors. No patient died of disease. Hibernoma is a tumor found most often in adults and most commonly in the thigh, with several morphologic variants. It is a benign tumor that does not recur with complete excision. Hibernomas should not be confused with atypical lipomas or well-differentiated liposarcoma.

Retroperitoneal and scrotal giant liposarcoma: report of a case

The case of a 63 year-old man with a giant scrotal and retroperitoneal tumor is herein reported. The initial symptoms began in the scrotum and subsequent abdominal distention resulted in discomfort 2 years later. The intraabdominal organs were under pressure because of the bulky mass, and the patient had dyspnea. Ultrasonograpy, computed tomography, and fine needle aspiration biopsy investigations all revealed a retroperitoneal tumor suspected to be liposarcoma. At operation, a tumor weighing 42 kg was excised. Respiratory support was provided in the early postoperative period. The histopathological diagnosis was myxoid liposarcoma. The patient was discharged from the hospital 14 days after the operation and was scheduled to undergo radiotherapy.

The ultrastructure of liposarcomas with attention to "dedifferentiation"

Liposarcomas are among the most common soft tissue sarcomas. It is recognized that dedifferentiation can occur within a well-differentiated liposarcoma, but there is limited information concerning the ultrastructure of the dedifferentiated cells. A series of 8 cases has been studied by light and electron microscopy and compared with well-differentiated, myxoid, and pleomorphic liposarcomas. No definite evidence of lipoblastic differentiation could be found in the dedifferentiated cases. The tumor cells resembled atypical cells in the well-differentiated liposarcomas, supporting the close relationship between these two types of tumors. However, since no conclusive line of differentiation could be found in the dedifferentiated cases, this study supports the contention that these neoplasms are undifferentiated counterparts of well-differentiated liposarcomas.

Thymus-related liposarcoma: report of a case and review of the literature

We report herein the case of a 77-year-old woman who was admitted to our hospital for further evaluation of an abnormal shadow in the right upper mediastinum that had been revealed by a routine chest X-ray. Computed tomography (CT) and magnetic resonance imaging (MRI) scans confirmed the presence of a thymic tumor, but did not show any evidence of invasion into the central vessels or adjacent structures. Thus, an extended thymectomy with resection of the tumor was performed. Microscopically, normal thymic tissue was found among the tumor cells, and a pathological diagnosis of well-differentiated liposarcoma was established. From the operative and microscopic findings, it is apparent that the tumor was related to the thymus. Postoperative irradiation of 60 Gy was delivered to the operative site and the patient has remained free of disease for 29 months since the operation.

Chondroid lipoma: an ultrastructural and immunohistochemical analysis with further observations regarding its differentiation

Chondroid lipoma was recently described as a unique, benign, pseudosarcomatous lipomatous tumor with chondroid features, often simulating liposarcoma and myxoid chondrosarcoma. An extended histochemical and immunohistochemical analysis of 13 cases, including the proliferation markers, proliferating cell nuclear antigen (PCNA) and Ki67, as well as ultrastructural studies of eight cases were performed with the intent of further elucidating its differentiation. Staining with toluidine blue and alcian blue at controlled pHs indicated the presence of chondroitin sulfates within the myxohyaline matrix. Immunohistochemically, all tumors were positive for vimentin and S100 protein. Focal immunoreactivity for cytokeratins was seen in 3 of 13 cases; one of these also had intracytoplasmic tonofilament bundles ultrastructurally. Scattered tumor cells stained for CD68 antigen with KP1 in 6 of 13 cases. None of the tumors stained for epithelial membrane antigen (EMA) or alpha-smooth muscle actin. Collagen IV immunostains showed a network of fibrils encircling individual tumor cells in 10 of 13 cases. Intracytoplasmic staining for laminin was found in 9 of 13 cases. Ultrastructurally there was a spectrum of differentiation, ranging from primitive cells sharing features of prelipoblasts and chondroblasts, to lipoblasts and preadipocytes, to mature adipocytes. A striking ultrastructural feature in 5 of 8 cases was the presence of knob-like protrusions of the cell membrane, which contained granular, amorphous, and fibrillar material that appeared to be extruded into the adjacent matrix. The myxohyaline matrix had ultrastructural features of cartilage. Numerous mitochondria and lysosomes were absent, indicating that chondroid lipoma is neither a hibernomatous lesion nor a lipogranuloma. Ki67 immunoreactivity was typically very low and detected only in the more primitive cell population. The findings in this analysis indicate that chondroid lipoma is a pseudosarcomatous lipogenic neoplasm with a unique cell population possessing predominantly features of embryonal fat and, to a lesser extent, embryonal cartilage.

Fine needle aspiration cytology of myxoid liposarcoma; a study of 18 tumours

The cytological features of 18 myxoid liposarcomas from 12 patients were analysed. The most consistent cytological features were: abundant myxoid matrix, several small tissue fragments with uniform small, round or stellate cells and a network of branching thin-walled capillaries. The presence of univacoulated or multivacuolated lipoblasts was noted frequently, but not in all aspirates. The diagnostic importance of vacuolated lipoblasts and the main problems of differential cytodiagnosis are discussed.

Primary liposarcoma of the mediastinum in a child

A case of primary anterior mediastinal liposarcoma occurring in a child is reported. A 5-year-old male child complained of exertional dyspnea and left chestpain. The chest roentgenogram showed a complete opacity of the left pleural space. After thoracotomy, the histological examination revealed mediastinal myxoid-pleomorphic liposarcoma. Surgical resection was performed and chemotherapy was given; 10 months later a recurrence was noted in the mediastinum. The child died 17 months after establishing the diagnosis.

Comparative ultrastructure of soft-tissue myxoid tumors

This comparative analysis of the characteristic ultrastructural features specific for intramuscular myxoma, myxoid liposarcoma, extraskeletal myxoid chondrosarcoma, myxoid malignant fibrous histiocytoma, myxoid variant of dermatofibrosarcoma protuberans, and myxoid neurilemmoma is based on our own studies of 52 cases. In spite of the histologic resemblance frequently observed, these tumors can be easily distinguished on the basis of cytoplasmic and extracellular features by electron microscopy. The value of electron microscopy in the diagnosis of myxoid tumors of soft tissues lies mainly in its potential to provide additional information concerning the cell types involved in the neoplastic process and their line of differentiation.

Distribution of collagen type IV in soft tissue tumors. An immunohistochemical study

The distribution of collagen type IV, one of the major constituents of basement membrane, was studied immunohistologically in a series of 103 soft tissue tumors including those of peripheral nerve origin, smooth muscle origin, striated muscle origin, fibrous tissue origin, fibrohistiocytic origin, adipose tissue origin, synovial tissue origin, and blood vessel origin, paragangliomas, alveolar soft part sarcomas, granular cell tumors, and epithelioid sarcomas. Intensely positive staining for collagen type IV was observed in neurilemomas, neurofibromas, malignant schwannomas, and blood vessel tumors. Weakly to moderately positive staining was seen in leiomyomas, angiomyomas, and leiomyosarcomas. In contrast, synovial, fibroblastic and fibrohistiocytic tumors, benign or malignant, were negative. In paragangliomas, granular cell tumors, and alveolar soft part sarcomas, positive staining was evident surrounding nests or clusters of tumor cells. In all tumors, staining for collagen type IV clearly illustrated the vascular pattern.

Myxoid malignant fibrous histiocytoma versus myxoid liposarcoma. A comparative ultrastructural study

An ultrastructural comparison of 7 examples of myxoid malignant fibrous histiocytoma (myxoid MFH) with 6 of myxoid liposarcoma is described. Despite certain histological differences between the two, electron microscopy was more valuable in differentiating MFH from liposarcoma. Electron microscopically, MFH contained a variety of cell types including histiocyte-like, fibroblast-like, intermediate-type, xanthomatous, multinucleated tumor giant cells and undifferentiated cells. Liposarcoma was composed mainly of lipoblasts at various stages of differentiation with a minority of undifferentiated cells and fibroblast-like cells. In contrast to the component cells of the MFH, these lipoblasts were characterized by abundant cytoplasmic glycogen, numerous pinocytotic vesicles and a discontinuous basal lamina in addition to large lipid droplets.

Inverted papillomas of nasal cavity and paranasal sinuses. Ultrastructural investigations on epithelial-stromal interface

10 cases of inverted papillomas of nasal cavity and paranasal sinuses were examined electron microscopically with particular regard to the epithelial-stromal interface. The papilloma cells were clearly demarcated from the stromal tissue by a basement membrane-like material. However, this structure mainly consisted of two or more layers, occasional breaks in the basement membrane were visible. Within the basal epithelial cells resting on the basement membrane accumulations of actin-like microfilaments could sometimes be observed. Furthermore, in the stromal tissue some myofibroblasts were present in the vicinity of the papillomatous cell complexes and capillary vessels also demonstrated several layers of basement membrane. All the changes presented here are considered to be the result of a permanent interaction between aggressive forces of papilloma cells and the defence mechanism of stromal tissue. The results allow the conclusion that inverted papillomas of nasal cavity and paranasal sinuses are true neoplasms with very low malignancy.