Biomedical subjects

L Angervall

Publications and source records attributed to L Angervall.

At least 19 recordsLinked to original sources

PubMed1999

Large cell, epithelioid, telangiectatic osteoblastoma: a unique pseudosarcomatous variant of osteoblastoma.

A previously undescribed large-cell, epithelioid, and aneurysmal variant of osteoblastoma with minimal osteoid-production--simulating telangiectatic osteosarcoma, epithelioid angiosarcoma, and metastatic carcinoma is reported. The tumor occurred in the mandible of a 14-year-old girl. The light microscopic, immunohistochemical, ultrastructural, cell proliferation, and DNA-ploidy studies, as well as the 7-year disease-free follow-up period all indicate a benign osteoblastic tumor. Cytogenetically, the tumor had a pseudodiploid karyotype, distinguished by a complex t(1;5;17;22) and a terminal 1q deletion. Recognition of this unique, pseudomalignant variant of osteoblastoma is important to avoid an erroneous diagnosis of malignancy.

Adolescent↗

PubMed1997

Malignant and benign tumors in patients with neurofibromatosis type 1 in a defined Swedish population.

BACKGROUND: The development of malignant and benign tumors in patient with neurofibromatosis type 1 (NF1) was investigated in a long term follow-up study of 70 adult NF1 patients living in Göteborg, Sweden, on January 1, 1978. Their mean age at that time was 44 years (range, 20-81 years). The 70 NF1 patients had previously been investigated in a population-based study. METHODS: The first part of this study involved a cancer registry study. The authors compared the number of tumors in the 70 NF1 patients reported to the Swedish Cancer Registry during the period 1978-1989 with the number of tumors expected in the general population by matching the incidence rates of the two populations specific to age, time of follow-up, and gender. The 95% confidence interval for the risk quotient between the risk to the patients and the risk to the general population was estimated. The second part of the study was a clinical pathologic follow-up study. All living patients were offered a clinical reexamination in 1990. All hospital records for all the NF1 patients were reviewed, and death certificates were also reviewed when available. RESULTS: Malignant tumors were reported to the Cancer Registry four times as often in the NF1 patient group as in the general population (95% confidence interval, 2.1-7.6) during the follow-up period 1978-1989. Before 1978, 5 of 70 patients (7%) had 6 malignant tumors; these patients were not included in the Cancer Registry study. Using all available clinical data on the 70 NF1 patients from their birth up to 1990, the authors found that 17 of 70 patients (24%) had developed a total of 19 malignant tumors, namely, 5 sarcomas (in 7% of patients), 13 carcinomas (in 16%), and 1 malignant melanoma (in 1%). Four pheochromocytomas (in 6% of patients), 2 adenomas, and 1 C-cell hyperplasia were diagnosed. Five gastrointestinal stromal tumors (in 7% of patients) were also diagnosed. CONCLUSIONS: Malignant tumors were reported to the Swedish Cancer Registry significantly more often in the NF1 patients than was expected in the general population matched for age, gender, and time of follow-up. The development of tumors is part of the NF1 disease process, and this deserves attention both in the clinical setting and in family counseling dealing with complications of NF1 in adulthood.

Adrenal Gland Neoplasms↗

PubMed1995

Life expectancy, mortality and prognostic factors in neurofibromatosis type 1. A twelve-year follow-up of an epidemiological study in Göteborg, Sweden.

Neurofibromatosis type 1 (NF1) is a genetic disease with an extremely wide range of manifestations. As yet, the individual course of NF1 cannot be predicted, and it is uncertain to what extent the disorder is associated with increased mortality. In order to gain insights into these aspects, we have conducted a 12-year follow-up study of 70 adult NF1 patients in the city of Göteborg, Sweden, whereby life expectancy, mortality, causes of death and the prognostic value of clinical findings were investigated. Clinical examinations were made, and all available records, including medical files, death certificates, and autopsy reports were scrutinized. The survival in the NF1 cohort was compared to that in the general Swedish population. Twenty-two deaths occurred in the NF1 group, whereas 5.1 deaths were expected in the general Swedish population (p = < 0.001). The mean age at death was 61.6 years. Malignancy was found in 12 (55%) of the deceased (soft tissue sarcomas in 3, and carcinomas in 9). Severe complications related to NF1 were seen in 27%. Hypertension was significantly associated with increased mortality, as 10 out of 12 (83%) patients with hypertension died during the observation period. NF1 was associated with increased mortality due to malignancy and NF1-related complications.

Adult↗

PubMed1994

Pseudomalignant spindle cell proliferations of the urinary bladder.

Twelve cases of polypoid, nonrecurrent, pseudomalignant spindle cell proliferations of the urinary bladder (eight women and four men) were analyzed. Two patients had a simultaneous urinary bladder carcinoma. The lesions were characterized by proliferating spindle- or strap-shaped cells, which on electron microscopic examination (performed in all 12 cases) revealed characteristics of fibroblasts and myofibroblasts. The cells showed immunoreactivity for vimentin in all cases, for alpha-smooth muscle-specific and muscle-specific actin in six cases, for cytokeratins in five cases, and for CD 34 in one case. No immunoreactivity was observed for desmin, myoglobin, epithelial membrane antigen, S-100 protein, endothelial cell antigen (H and Y), CD 68, or factor VIII RAG. Immunoreactivity for Ki-67 and proliferating cell nuclear antigen was detected in up to 30% of the spindle cell nuclei. The static cytometric DNA analysis revealed a diploid, or in two cases a hyperdiploid, stem cell line. An awareness of this type of spindle cell lesion and its immunophenotypic characteristics and diversity is of importance to avoid an erroneous diagnosis of spindle cell sarcoma (in particular leiomyosarcoma and embryonal rhabdomyosarcoma) or spindle cell carcinoma.

Actins↗

PubMed1993

Infantile rhabdomyofibrosarcoma: a high-grade sarcoma distinguishable from infantile fibrosarcoma and rhabdomyosarcoma.

Three patients with a predominantly fibrosarcomatous, desmoplastic, and fascicular spindle-cell sarcoma, resembling that of infantile fibrosarcoma but with ultrastructural and immunocytochemical evidence of rhabdomyoblastic differentiation, are described. The tumors were compared light and electron microscopically and immunocytochemically with six classical cases of infantile fibrosarcoma of the desmoplastic type. The three tumors occurred in two girls and one boy who were between 1 and 3 years of age. Ultrastructurally, the tumor cells primarily demonstrated fibroblastic and myofibroblastic features, but there were also tumor cells with sarcomere-like structures. The spindle-shaped, fibroblast-like tumor cells expressed vimentin, desmin, and smooth muscle-specific and sarcomere-specific actins. In one tumor peculiar intracytoplasmic inclusions were observed by light and electron microscopy. The immunocytochemical analysis indicated that these bodies contained all types of thin and intermediate filaments. In short-term cell cultures the tumor cells of two examined tumors revealed immunoreactivity for vimentin, smooth muscle-specific actin, and desmin. Cytogenetically, both tumors displayed a similar chromosomal pattern. One tumor contained two abnormal clones with monosomy 19 and monosomy 22, respectively, and the other tumor revealed a single clone with monosomy 19. In addition, both tumors contained clones with a normal karyotype. Two of the patients with metastatic spread died within 2 years of the primary operation. The third patient is alive with a local recurrence. The three tumors described here deviate from infantile fibrosarcoma in terms of their clinical, ultrastructural, immunocytochemical, and cytogenetic characteristics. The descriptive term "infantile rhabdomyofibrosarcoma" is suggested. The present investigation calls for detailed studies of tumors diagnosed as infantile fibrosarcomas that have metastasized and followed a fatal course.

Child, Preschool↗

PubMed1993

Principles for pathologic-anatomic diagnosis and classification of soft-tissue sarcomas.

Soft-tissue tumors are classified as frankly or potentially malignant, and as benign tumors and tumor-like lesions that can mimic soft-tissue sarcomas and other malignancies. Classification of soft-tissue sarcomas is based on knowledge or assumption of cell and tissue origin and differentiation. New principles and methods are used for the pathologic-anatomic diagnosis of these lesions. With increasing research on chromosomal aberrations and molecular biology, knowledge of the biology of soft-tissue sarcomas will grow, which in turn, will further revise current tumor classifications.

Biopsy, Needle↗

PubMed1992

Metastasizing gastric epithelioid leiomyosarcomas (leiomyoblastomas) in young individuals with long-term survival.

RESULTS. Four patients with metastasizing epithelioid leiomyosarcoma of the stomach, three females and one male (15, 20, 22, and 25 years of age, respectively), are reported. Two patients had recurrent tumors in the gastric remnant. Liver metastases occurred in all patients, three of whom had lymph node metastases; two had peritoneal metastases. The patients are alive at 17, 19, 27 and 48 years after the diagnosis was made and 17-27 years after the first demonstration of metastases. One woman had multiple chondromatous hamartomas of the lung. Operations were performed when the patients had symptoms and during periods of no symptoms, as directed by the second-look principle. One patient had 10 operations. None of the patients received adjuvant therapy. All three women have given birth to healthy children after metastases were diagnosed. Three of the primary tumors were large (10-20 cm) and multinodular, features that have been associated with unfavorable prognosis. The four primary tumors had a similar light microscopic appearance, characterized by moderate cell and nuclear pleomorphism and low mitotic activity, 0.03-0.1/mm2. Ultrastructurally, a network of intermediate filaments was found within the cytoplasm of the tumor cells corresponding to the immunohistochemical positivity for vimentin. The immunohistochemical findings (negative immunoreaction for desmin and alpha smooth-muscle actin) and the ultrastructural analysis produced no evidence of the production of smooth-muscle cell myofilaments. However, there were tumor cells with an abundance of mitochondria and a paucity of filaments, features that may be characteristic of epithelioid leiomyomatous tumors. In addition, immunohistochemical negativity for cytokeratins, epithelial membrane antigen, S-100 protein, neuron-specific enolase, and chromogranin militate against an epithelial or neuroectodermal cell differentiation. CONCLUSIONS. An awareness of this type of gastric leiomyosarcoma in children and young adults is of importance in making correct assessments of prognosis and choosing an active therapeutic approach. The biologic background to the clinical behavior of these metastasizing tumors remains an enigma. Additional studies are needed to elucidate the biology of these tumors.

Adolescent↗

PubMed1992

Reciprocal translocation t(12;22)(q13;q13) in clear-cell sarcoma of tendons and aponeuroses.

Clear-cell sarcoma is a rare soft tissue sarcoma that displays certain similarities to malignant melanoma. In this paper we describe the karyotypic findings and in vitro growth characteristics of a short-term-cultured clear-cell sarcoma. The cultured tumor cells had preserved immunohistochemical characteristics and certain ultrastructural features of the primary tumour, including positivity for vimentin, S-100 protein, and a melanoma-associated antigen, supporting the authenticity of the cultured cells. Cytogenetic analysis revealed an abnormal stemline karyotype of 49,XY, -1, +8, +8, +12, +der(1)t(1;?)(p36.1-.3;?), t(12;22)(q13;q13). A similar or identical t(12;22) was recently reported in two of four clear-cell sarcomas. It is suggested that the t(12;22)(q13;q13) is a primary cytogenetic abnormality in clear-cell sarcoma and distinguishes this tumor type from malignant melanoma.

Adult↗

PubMed1992

Plexiform fibrohistiocytic tumor. Report of a case involving preoperative aspiration cytology and immunohistochemical and ultrastructural analysis of surgical specimens.

A typical case of plexiform fibrohistiocytic tumor (Enzinger and Zhang) occurring in the skin and subcutis of the abdominal wall in a 7-year-old girl is reported. Preoperative fine-needle aspiration cytology revealed a benign lesion with fibroblastic-histiocytic features which also contained bi- and multinucleated giant cells. The surgical specimen showed a tumor with multiple small nodules within fibrous septa; these nodules were composed of spindle cells and epithelioid cells and contained scattered multinucleated osteoclast-like cells. The tumor cells showed ultrastructural and immunohistochemical features of myofibroblasts and histiocyte-like cells. Thus, there was an abundance of lysosomes, prominent filopodia and bundles of thin cytofilaments along the cytoplasmic border, as well as immunoreactivity for alpha-smooth-muscle-specific actin, alpha-1-antitrypsin and alpha-1-antichymotrypsin. Ultrastructurally there were tumor cells exhibiting features of histiocytes which also contained bundles of actin of smooth muscle type. The presented case of plexiform fibrohistiocytic tumor appears to be composed of a rather peculiar cell form, somewhere between myofibroblasts and histiocytes.

Abdominal Neoplasms↗

PubMed1992

Proliferative myositis and fasciitis. A light and electron microscopic, cytologic, DNA-cytometric and immunohistochemical study.

Two cases of proliferative myositis, four cases of proliferative fasciitis and one mixed form of proliferative myositis and fasciitis have been analyzed in terms of cell differentiation and DNA content. Light microscopically, the lesions were characterized by a mixture of proliferating spindle-shaped cells and uni-, bi- or occasionally multinucleated ganglion cell-like cells. The spindle cells showed ultrastructural features and immunohistochemical properties, including an immunoreactivity for smooth muscle-specific actin, indicative of a myofibroblastic differentiation. The ganglion cell-like cells displayed some resemblance to active osteoblasts ultrastructurally and differed immunohistochemically from the spindle cells by being non-immunoreactive for smooth muscle-specific actin. None of the two cell types showed immunoreactivity for desmin, myoglobin or factor VIII RAG. It is suggested that the two cell types represent different lines of cell differentiation. The cytologic features in smears, as seen in two cases of proliferative fasciitis and one case of proliferative myositis, are considered to be characteristic of these lesions and to permit the diagnosis to be made by fine-needle aspiration. In two of the cases, the lesion was diagnosed only cytologically and thereafter disappeared spontaneously within a month. Cytometric DNA measurements, using two different image analysis systems on Feulgen-stained sections and smears, revealed a "diploid" spindle-shaped cell population with a variable proportion of cells with scattered DNA values. The ganglion cell-like cells differed from the spindle cells by having a broad DNA peak in the diploid region and additional peaks in the tetraploid region, as well as a higher proportion of cells with scattered DNA values compared with those of the spindle-shaped cells. The results of the quantitative DNA analysis are well in keeping with the benign and proliferative nature of these lesions. However, with the technique used here, quantitative DNA analysis, does not distinguish these pseudosarcomatous fibrous lesions from diploid and tetraploid soft tissue sarcomas.

Actins↗

PubMed1991

Morphological and cytogenetic studies of angiosarcoma in Stewart-Treves syndrome.

A morphological and cytogenetic analysis of a multifocal angiosarcoma in a typical case of Stewart-Treves syndrome is reported. The morphological analysis indicated differentiation along both blood and lymph vessel endothelium lines. By light and electron microscopy there were areas with well-developed erythrocyte-containing, capillary-like vessels and poorly differentiated areas with abortive vascular formations. In these the endothelium revealed immunoreactivity to factor VIII RAg, binding of Ulex europaeus I and Psophocarpus tetragonolobus agglutinin lectins, Weibel-Palade bodies ultrastructurally and presented a continuous enclosing external lamina and immunoreactivity for laminin and collagen IV, all features of blood-vessel differentiation. There were also lymphangioma-like areas as well as poorly differentiated areas where the immunohistochemical, lectin-binding and ultrastructural features were compatible with a lymph vessel differentiation. Cytogenetic analysis of cultured tumour cells revealed chromosome counts in the diploid region. About 40% of the cells analysed had a normal diploid karyotype. The remaining cells showed a multitude of mainly nonclonal structural alterations; 17 unique marker types resulting from different translocations and deletions were observed. There were also a few cells with clonal numerical deviations showing monosomy 22, monosomy X and trisomy 2 respectively. It is of interest that the losses of chromosome 22 and the X chromosome also have been observed in Kaposi's sarcoma and that the PD-ECGF gene, a novel angiogenetic factor, has been mapped to chromosome 22.

Adult↗

PubMed1991

Clonal chromosome abnormalities and in vitro growth characteristics of classical and cellular schwannomas.

Cytogenetic analysis was performed on 12 schwannomas, 10 classical and two of the cellular type. Electron microscopic examination of cultured cells from two classical and two cellular schwannomas revealed features compatible with a Schwann cell differentiation. Immunohistochemical analysis of the cultures demonstrated immunoreactivity for S-100 protein in 6 of 6 cases and for vimentin in 2 of 2 cases of classical schwannoma, thus further supporting the authenticity of the cultured cells. Cultured cells from one cellular schwannoma also exhibited immunoreactivity for glial fibrillary acid protein (GFAP). Cytogenetic analysis of the 12 tumors revealed clonal abnormalities in 10 of the cases. In the majority of tumors, cells with a normal karyotype coexisted with different abnormal clones and sporadic deviations. Numerical changes predominated and were found in all tumors, while structural rearrangements were detected in eight tumors. The most common abnormality was clonal or sporadic loss of chromosome 22, which was found in all cases. Other clonal abnormalities included loss of one sex chromosome found in five cases, -15 found in three cases, and -12, +5, +7, +20 found in two cases each. These results provide further evidence in support of a role for loss of chromosome 22 in the pathogenesis of schwannomas. Our findings also indicate that there exist several different evolutionary pathways for schwannomas, and that some of these are shared by several other types of benign and malignant tumors of the nervous system.

Adult↗

PubMed1991

Classical and chondroid chordoma. A light-microscopic, histochemical, ultrastructural and immunohistochemical analysis of the various cell types.

The aim of the present investigation was to characterize the various cell types of classical and chondroid chordomas. Eight cases of classical chordoma, 1 case of sacrococcygeal chordoma with chondroid areas and 2 cases of spheno-occipital chondroid chordoma were studied. Ultrastructurally and immunohistochemically (immunoreactivity for cytokeratins, epithelial membrane antigen [EMA], tissue polypeptide antigen [TPA] and human milk fat globule protein [HMFG]) the 3 cell types (physaliferous, epithelial-like, and spindle-shaped) recognized light-microscopically presented features of epithelial differentiation and rather formed a continuous spectrum than being distinct cell types. The chondroid areas of the chondroid chordomas had similar ultrastructural and immunohistochemical properties except for the lack of immunoreactivity for EMA and HMFG. The results of the critical electrolyte concentration technique according to Scott and Dorling indicated that there was no difference in the sulfated glycosaminoglycan content between classical and chondroid chordomas: all the tumors contained chondroitin sulfate. The presence of chondroitin sulfate, immunoreactivity for vimentin and S-100 protein and areas of cartilaginous differentiation in three cases indicate a relationship both to chondromatous tumors and to normal notochord, from which chordoma is believed to originate.

Adult↗

PubMed1991

Intermediate and fine cytofilaments in cutaneous and subcutaneous leiomyosarcomas.

The expression of fine and intermediate cytofilaments in 10 cutaneous and seven subcutaneous leiomyosarcomas was studied immunohistochemically. All the tumors contained tumor cells which showed a positive immunoreactivity for desmin in formaldehyde-fixed and paraffin-embedded sections, but none of the seven anti-desmin antibodies used alone produced a distinct positive staining in all the tumors. A lack of correspondence in terms of immunoreactivity between tumor cells and the supposed muscle of origin was observed, especially in the subcutaneous leiomyosarcomas. In all cases, antibodies to muscle-specific and smooth muscle-specific actin were found to produce a positive staining in both the tumors and the supposed muscle of origin. Vimentin was detected in 8/10 cutaneous and 4/7 subcutaneous leiomyosarcomas, while the supposed muscle of origin was positive in 3/10 and 7/7 cases, respectively. Four of the cutaneous and three of the subcutaneous leiomyosarcomas contained tumor cells which stained positively for cytokeratins, while the supposed muscle of origin showed no positivity. It thus appears that a phenotypic shift in terms of vimentin and cytokeratin expression occurs in the tumor cells of cutaneous and subcutaneous leiomyosarcomas compared with the supposed muscle of origin. It is recommended that more than one monoclonal anti-desmin antibody is used to characterize these tumor entities. It is also concluded that the immunoreactivity for muscle-specific actins in superficial leiomyosarcomas is more constant, although less specific, than that of desmin and that the demonstration of the simultaneous expression of muscle-specific actins and desmin is helpful.

Actin Cytoskeleton↗

PubMed1990

A cell culture, chromosomal and quantitative DNA analysis of a metastatic epithelioid sarcoma. Deletion 1p, a possible primary chromosomal abnormality in epithelioid sarcoma.

The chromosomal banding pattern and the in vitro growth characteristics of a metastatic epithelioid sarcoma are described. The cultured tumor cells retained growth characteristics as well as ultrastructural and immunohistochemical properties similar to the cells of the primary tumor. Cytogenetic analysis revealed a modal range in the diploid-hypodiploid region, a finding which was corroborated by quantitative DNA determinations of both the primary tumor and a lymph node metastasis. Fourteen different marker chromosomes were identified. The most frequent clonal rearrangement was a 1p-marker resulting from a short arm terminal deletion, i.e., del (1) (p21-22). A similar 1p- marker has previously been observed in an established epithelioid sarcoma cell line. The finding of an apparently identical 1p-marker in two of two analyzed epithelioid sarcomas suggests that this rearrangement may be a primary cytogenetic abnormality in epithelioid sarcoma. An elevated ras p21 expression was demonstrated using immunohistochemical methods. The possible involvement of the N-ras gene and/or a tumor suppressor in the 1p deletion is considered.

Chromosome Aberrations↗

PubMed1990

Metastases of malignant melanoma simulating soft tissue sarcoma. A clinico-pathological, light- and electron microscopic and immunohistochemical study of 21 cases.

Metastases of cutaneous malignant melanoma (MM) of ordinary type can resemble various types of soft tissue sarcoma light microscopically to a degree which has not been previously recognized. Twenty-one cases are described, in which the tumours were originally diagnosed as a soft tissue sarcoma. Seven tumours were predominantly of blue and spindle-cell, fascicular type, resembling malignant peripheral nerve sheath tumour and at times monophasic synovial sarcoma. Ten tumours which were of fascicular and predominantly storiform type, and included uni- and multi-nuleated pleomorphic cells resembled malignant fibrous histiocytoma. Due to the presence of multivacuolated lipoblast-like tumour cells, 2 of these 10 tumours resembled pleomorphic liposarcoma. One had a predominantly myxoid and hypocellular appearance and 5 additional tumours included such areas. The diagnoses were revised after ultrastructural examination with the demonstration of melanosomes in 13 of 16 studied cases and the immunohistochemical demonstration of positivity using anti-S-100 protein antibodies and the anti-melanoma antibody NKI/C3 in all cases. The anti-melanoma antibody HMB 45 gave a positivity in 9 of 21 cases. Light microscopically, sparse amounts of melanin were noted in 7 tumours using the Whartin-Starry technique. Eleven tumours occurred at sites close to major lymph node groups and in 9 of these cases, lymphoid tissue was associated with the tumours, suggesting that they represented lymph node metastases. Following a review of the patients' clinical histories and renewed clinical examination, primary cutaneous MM was demonstrated in 10 of 21 patients and in 1 case an MM in regression was detected. The origin of the 10 tumours without a detected primary is discussed, including the possibility of an overlooked primary, spontaneous regression of a primary and a de novo origin from lymph nodes and soft tissues.

Adolescent↗

PubMed1990

Cellular schwannoma. A clinicopathologic study of 29 cases.

A series of 29 cellular schwannomas is described in terms of their clinical presentation and course, light and electron-microscopic appearance, immunohistochemical properties and cytogenetics. The study indicates that cellular schwannoma can be defined as a subtype of classical schwannoma, characterized by spindle cells forming a compact fascicular, sometimes fibrosarcoma-like growth pattern, a low mitotic activity, a generally moderate nuclear and cellular polymorphism and a high degree of Schwann cell differentiation as seen by electron microscopy and immunohistochemistry. The tumour is characteristically located close to the vertebral column, in the mediastinum or retroperitoneum and has a benign course. Occasionally bone destruction and neurological symptoms develop. The clinical appearance together with the high cellularity, fascicular pattern and mitotic activity had led to the erroneous diagnosis of a soft tissue sarcoma in a few cases, and cellular schwannoma may thus be considered to be a pseudosarcoma. Immunohistochemically, cellular schwannomas appear to deviate from classical schwannomas and malignant peripheral nerve sheath tumours by their expression of glial fibrillary acidic protein. The chromosome analysis revealed a normal diploid stemline karyotype, with a variety of abnormal clones, including one with monosomy 22.

Adolescent↗

PubMed1990

Expression of muscle-specific actins and myosin in light microscopically undifferentiated small and dark cell malignancies of soft tissues.

Eighteen light microscopically undifferentiated small and dark cell malignancies, previously studied ultrastructurally and immunohistochemically in terms of desmin, vimentin and myoglobin expression, were analyzed using mono- and polyclonal antibodies to muscle-specific isoforms of myosin and actin. For comparison, 10 characteristic rhabdomyosarcomas, 5 alveolar and 5 embryonal, were included in the study. A polyclonal antibody to skeletal myosin produced an indistinct staining in all the alveolar and embryonal rhabdomyosarcomas. The staining was most prominent in well-differentiated rhabdomyoblastic tumor cells. In the analysis of the small and dark cell malignancies, this antibody produced a weak and indistinct positivity which can not be interpreted with certainty as an expression of muscle-specific properties. An antibody directed at the alpha and gamma isoforms of actin, which are present in smooth and striated muscle, produced a distinct positive staining in all the alveolar and embryonal rhabdomyosarcomas and in 8/18 small and dark cell malignancies, 7 of which were also shown to express desmin. An antibody directed at the alfa-smooth muscle isoform of actin did not produce any positive staining in any of the tumors. The present study indicates that both muscle-specific actin and desmin can be expressed in tumors lacking ultrastructural evidence of a rhabdomyoblastic differentiation and that the combined use of monoclonal antibodies to desmin and muscle-specific actin is of value when it comes to recognizing rhabdomyosarcomas within the group of undifferentiated small and dark cell malignancies of soft tissue tumors.

Actins↗