Rhabdomyosarcoma in children: ultrastructural study of 31 cases

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

Early history of pathology studies by the Intergroup Rhabdomyosarcoma Study Group

This review chronicles the series of publications that were the result of the willingness of pathologists and clinicians in the United States to share their pathologic materials and clinical data on patients who were placed on treatment protocols for rhabdomyosarcoma and related tumors over an extended period of time. The availability of this database enabled pathologists and clinicians to study a tumor type that is rare in individual institutions, but occurs in large enough numbers to produce valid conclusions not otherwise possible. Furthermore, young investigators were challenged by this opportunity and were able to spend the necessary time to make new observations that, in retrospect, helped direct protocol designs that produced significant improvement in patient survival. The key factor in this process is the surrender of individual scientific prerogatives to a small number of investigators. It is also important to recognize that the pathologist component of these series of contributions is only a part of the entire effort. It takes an organization of gifted, dedicated experts in many disciplines working together. The investigators who served on the Intergroup Rhabdomyosarcoma Group over a 25-year period eminently fulfilled this.

Embryonal rhabdomyosarcoma of the nose in an elderly patient, case report and review of the literature

Embryonal rhabdomyosarcoma of the head and neck is very rare in adults. We report on an embryonal rhabdomyosarcoma of the nose, occuring in a 74-year-old female patient presenting with nasal congestion as the only clinical symptom. Suspected to be an amelanotic melanoma, further biopsies and histological examinations provided the correct diagnosis. She first underwent a course of chemotherapy which led to a partial shrinkage of the tumor mass which was followed by a complete resection of the residual tumor mass. Biologic behaviour of this tumor must be fully appreciated as treatment is interdisciplinary. Rhabdomyosarcoma should be considered in the differential diagnosis of tumors of the nose and paranasal sinuses not only in children, but also in adults.

Cutaneous malignant melanomas in 57 cats: identification of (amelanotic) signet-ring and balloon cell types and verification of their origin by immunohistochemistry, electron microscopy, and in situ hybridization

Cutaneous malignant melanomas in cats, both melanotic and amelanotic, were diagnosed in 57 of 1.530 skin tumors during the period 1991-1995. All melanomas occurred in domestic shorthaircats of ages 3-19 years (mean = 11.5 years). Postmortem examination was performed on 16 cats. All had metastases in the regional lymph node and several organ systems. The average time of survival after surgical removal of the tumor was 4.5 months. Histologically, five types of melanomas could be distinguished: epithelioid, spindle, mixed, signet-ring, and balloon cell. Whereas all epithelioid, spindle, and mixed epithelioid/spindle cell types showed pigmentation, signet-ring and balloon cell types were often amelanotic. Immunohistochemical examination of the melanomas revealed a positive staining for S-100, vimentin, and neuron-specific enolase. The melanomas were negative for muscle cell markers, except in some of the signet-ring cell melanomas; 13 of 21 tumors showed a weak positive staining for polyclonal desmin. Electron microscopic examination of signet-ring cell melanomas revealed an abundance of intermediate filaments, whereas in some of these tumors a few cells with melanosomes were found. Nonisotopic in situ hybridization for mRNA encoding for tyrosinase verified the melanocytic origin of the amelanotic signet-ring and balloon cell melanomas.

Ultrastructure of cellular congenital mesoblastic nephroma

A detailed ultrastructural description of the cellular variant of congenital mesoblastic nephroma (CMN) is presented and compared to the classical form. Studied were 9 cases of the cellular variant, 6 mixed (cellular/classical) tumors, and 1 classical CMN. The occurrence of a broad selection of ultrastructural features was assessed using a semiquantitative scoring system. The results indicate that cellular CMNs are composed mainly of primitive mesenchymal cells, but also usually contain varying numbers of differentiating fibroblasts and myofibroblasts. This entity thus bears a closer resemblance at the ultrastructural level of organization to infantile fibrosarcoma than to conventional fibrosarcoma. Electron microscopy can be useful in distinguishing this relatively benign entity from the several malignancies with which it is sometimes confused.

Classification of rhabdomyosarcomas and related sarcomas. Pathologic aspects and proposal for a new classification--an Intergroup Rhabdomyosarcoma Study

BACKGROUND

There is a need to develop a single prognostically significant classification of rhabdomyosarcomas (RMS) and other related tumors of children, adolescents, and young adults which would be a current guide for their diagnosis, allow valid comparison of outcomes between protocols carried out anywhere in the world, and should enhance recognition of prognostic subsets.

METHOD

Sixteen pathologists from eight pathology groups, representing six countries and several cooperative groups, classified by four histopathologic classification schemes 800 representative tumors of the 999 eligible cases treated on Intergroup Rhabdomyosarcoma Study II. Each tumor was classified according to each of the four systems by each of the pathologists. In addition, two independent subsamples of 200 of the 800 patients were reviewed according to the new system, so that 343 distinct patients were reviewed once, and 57 of these twice.

RESULTS

A study of the survival rates of all subtypes in the sample of 800 patients led to the formation of a new system. This was tested on two independent subsets of 200 of the original cases and found to be reproducible and predictive of outcome by univariate analysis. A multivariate analysis of the 343 patients classified according to the new system indicated that a survival model including pathologic classification and known prognostic factors of primary site, clinical group, and tumor size was significantly better at predicting survival than a model with only the known prognostic factors.

CONCLUSION

This new classification, termed International Classification of Rhabdomyosarcoma (ICR) by the authors, was reproducible and predictive of outcome among patients with differing histologies treated uniformly on the Intergroup Rhabdomyosarcoma II protocols. We believe it should be utilized by all pathologists and cooperative groups to classify rhabdomyosarcomas in order to provide comparability among and within multi-institutional studies.

The expression pattern of contractile and intermediate filament proteins in developing skeletal muscle and rhabdomyosarcoma of childhood: diagnostic and prognostic utility

In order to investigate whether rhabdomyosarcoma (RMS) can be related to equivalent stages of skeletal muscle development, muscle tissue of 21 human foetuses and 112 primary RMSs were characterized immunohistochemically using antibodies directed against vimentin, desmin, muscle-specific actin (HHF35), sarcomeric actin (sr-actin), smooth muscle actin (sm-actin), and troponin-T. During fetal skeletal muscle development, all myotubes/fibres of the first and second generations expressed desmin, HHF35, and sr-actin. Vimentin was almost exclusively present in immature primary and secondary myotubes/fibres. Troponin-T was expressed in immature myotubes/fibres of the first and second generations as well as mature fibres of the second generation. Sm-actin was never expressed. Vimentin was expressed in 96 per cent of primary and 98 per cent of relapsed RMS; HHF35 in 96 and 98 per cent, respectively; desmin in 95 and 100 per cent; troponin-T in 82 and 75 per cent; sr-actin in 71 and 86 per cent; and sm-actin in 13 and 17 per cent. The proportion of RMS cells reacting with vimentin, HHF35, and desmin was consistently higher than those expressing sr-actin and troponin-T. Neither the shape nor size of neoplastic RMS cells nor the histopathological types were related to the expression pattern of the investigated markers. RMS with aberrant expression of two or more markers predicted a worse prognosis than RMS in which at most one marker was aberrantly expressed (25 per cent and 54 per cent 10-year survival, P = 0.01). These results demonstrate that HHF35, desmin, sr-actin, and troponin-T have the potential to confirm the commitment of the tumours to the myogenic pathway which supports the diagnosis of RMS. However, it was impossible to relate RMS to equivalent stages of skeletal muscle development. Aberrant marker expression by RMS cells correlated significantly with patients' survival.

Patterns of differentiation in extraosseous Ewing's sarcoma cells. An in vitro study

BACKGROUND

In vitro, tissue culture-associated differentiation assays have facilitated the identification of multiple tumor-cell types.

METHODS

We have investigated the capability of differentiation of three extraosseous Ewing's sarcoma cell lines toward a neural and muscular direction by in vitro stimulation with dibutyryl cyclic adenosine-monophosphate (db cAMP) and 5-azacytidine, respectively.

RESULTS

Elongation of cytoplasmic processes and increase of neural markers chromogranin, S-100 protein, and glial fibrillary acidic protein were observed after db cAMP treatment of these lines and neurosecretory granules as well as myelin figures were demonstrated ultrastructurally. These results support the existence of several pathways of neural differentiation in vitro--neuroblastic, Schwannian, and central glial--in stages of maturation more advanced than those previously reported in Ewing's sarcoma of bone. The cell lines showed no definitive myoblastic differentiation after 5-azacytidine treatment.

CONCLUSIONS

These data suggest that these three extraosseous Ewing's sarcoma cell lines configurate a heterogeneous group of tumors with respect to capability of differentiation into the neural lineage, arrested at more advanced stages of neural crest development than Ewing's sarcoma of bone and without capability of myoblastic differentiation with 5-azacytidine.

Rhabdomyosarcomas in young pigs in a swine breeding farm: a morphologic and immunohistochemical study

Within a 6-month-period, solitary or multiple tumors were observed in 25 young pigs in their first weeks of life in a swine breeding farm. The herd comprised approximately 100 animals, and affected pigs were observed in several litters. The number of affected littermates varied from one to three. Five animals, all from different litters and with a total of 11 tumors, were studied. Histologically the tumors were classified as undifferentiated sarcomas. Electron microscopic examination of the tumors (n = 3) revealed myogenic differentiation, characterized by the presence of numerous cytoplasmic filaments with longitudinal densities and cytoplasmic dense bodies. Immunohistochemically, all 11 tumors were labeled by vimentin and desmin antibodies. Two tumors from which frozen material was available were additionally labeled by a titin antibody but did not show immunoreactivity with antibodies directed against myosin and alpha-sarcomeric actin. The tumors were finally diagnosed as undifferentiated rhabdomyosarcomas. The high incidence of these tumors within a short period of time in multiple young animals in different litters indicates a common causative event. The clinical history suggests a genetic cause.

Fine-needle aspiration biopsy diagnosis of rhabdomyosarcoma: cytologic, histologic, and ultrastructural correlations

A series of 15 cases of rhabdomyosarcoma diagnosed by fine-needle aspiration biopsy (FNAB) and confirmed by histopathology is reviewed. Cytologically, the tumors were composed of a variable mixture of cells, which according to the degree of differentiation were categorized as early, intermediate, or late rhabdomyoblasts. Histologically, the tumors were divided into embryonal 9, monomorphic round cell 4, and alveolar rhabdomyosarcoma 2. Comparison of histological and cytological features revealed that embryonal types were composed mainly of early rhabdomyoblasts. Recognition of these patterns may be helpful in FNAB diagnosis of rhabdomyosarcoma.

12q13 abnormality in rhabdomyosarcoma. A nonrandom occurrence?

We describe two cases of rhabdomyosarcoma with a translocation involving 12q13 as the primary cytogenetic abnormality. Literature review of 35 cases has identified 3 other cases with this abnormality, and we speculate that this may be another nonrandom rearrangement in rhabdomyosarcoma.

Lipid-rich rhabdomyosarcoma--a potential source of diagnostic confusion

Rhabdomyosarcoma is an often primitive tumor capable of diverse morphologic manifestations. The article describes three cases of childhood rhabdomyosarcoma in which a significant population of lipid-rich tumor cells was present. The lack of specificity and potentially confusing nature of this feature are discussed, and the ultrastructural diagnosis of rhabdomyosarcoma is briefly reviewed.

Nondifferentiated-type small cell sarcoma of kidney in a young woman

A case of rapidly fatal small cell sarcoma of kidney in a young woman is described. Histologic, immunohistochemical, and ultrastructural studies demonstrated some features not reported previously in the literature, such as the arrangement of vimentin intermediate filaments in small irregular masses and the presence of various types of cytoplasmic projections. These findings, together with the observation of rare neoplastic elements with immunophenotypic and subcellular aspects of histiocytic and myofibroblastic differentiation, suggest that this tumor should be included in a group of small cell sarcomas of kidney lacking features of differentiation and should be considered a new variant occurring in adulthood.

Characterization of malignant mesenchymal cell line (UISO-RS-3) derived from a human rhabdomyosarcoma and inhibition by pharmacologic doses of estrogen

A new tumor cell line has been established from a malignant pleural effusion in a 28-yr-old female patient with a primary alveolar rhabdomyosarcoma of the left buttock. The in vitro and in vivo growth characteristics, morphologic features, abnormal karyotype, and immunohistochemical staining pattern indicate that this cell line is comprised of primitive malignant mesenchymal cells derived from a human rhabdomyosarcoma. Receptor studies done on tumors grown in male athymic mice revealed a single class of high affinity saturable cytoplasmic estrogen receptor (Bmax 2.6 fm/mg cytosol protein, Kd 0.34 nM). Likewise, sucrose density gradient analysis demonstrated specific low-capacity, high-affinity estradiol binding predominately in the 8S region. Cell growth in monolayer culture and on soft agar in the presence of estradiol was inhibited by pharmacologic concentrations of estradiol in a dose-responsive manner compared with control. We describe a newly characterized malignant mesenchymal cell line derived from an alveolar rhabdomyosarcoma that is inhibited by pharmacologic doses of estradiol in vitro. These findings suggest further investigation into the mechanism(s) of this estrogen-induced inhibition in rhabdomyosarcomas.

Experimentally induced murine rhabdomyosarcomas--correlation between cellular contacts, matrix formation and cellular differentiation

Rhabdomyosarcomas (RMSs) consist of a mixture of primitive mesenchymal cells as well as cells showing various stages of rhabdomyomatous differentiation. The qualitative and quantitative degree of the rhabdomyomatous differentiation of the cells, evaluated by their morphology and expression of defined structural and functional proteins, is accepted as the basis of diagnosis and is considered to be related to the biological behaviour of RMSs. Therefore we investigated solid experimentally induced murine RMSs, adherent (subconfluent, confluent) cell cultures obtained therefrom, and also suspension cultures and studied the expression of muscular differentiation markers (vimentin, desmin, myoglobin) and the formation of extracellular matrix components (fibronectin, laminin). When we compared solid tumours with adherent cell cultures of decreasing cell densities (confluent up to single cells) and with cells grown in suspension, we found a gradual decline of differentiation ("dedifferentiation"). This decline paralleled the decrease of cell-cell and cell-substrate contacts. In suspension cultures, cells were prevented from interacting with each other and the substratum, no rhabdomyomatous differentiation of the cells took place. If restoration of cellular contacts was allowed, either by adherent growth or by reinoculation into nude mice, the process of dedifferentiation was completely reversible. Consequently, it was demonstrated that the increase of cell-cell and cell-substrate contacts was strongly associated with the appearance or increasing expression of the desmin intermediate filament cytoskeleton and with formation of the extracellular matrix components fibronectin and laminin. The microfilament (F-actin) system was modulated from an impressive stress-fiber system in subconfluent to a dense network in confluent monolayers. The extent of cell-substrate contacts, mediated by extracellular matrix components, and the number of cell-cell interactions are responsible for the capability of a malignant mesenchymal cell, which is able to undergo rhabdomyomatous differentiation, to achieve the various stages of maturation.

The value of electronmicroscopy and immunohistochemistry in the diagnosis of soft tissue sarcomas: a study of 200 cases

Two hundred soft tissue sarcomas, accrued consecutively over a 4-year period, were examined by light and electronmicroscopy and by routine immunohistochemistry. The commonest tumour type was malignant fibrous histiocytoma. Fibrosarcoma, composed only of fibroblasts, was diagnosed in only one case; three others, composed also of myofibroblasts, could be regarded as fibrosarcomas or myofibrosarcomas. Immunohistochemistry was of most value in the diagnosis of rhabdomyosarcoma, leiomyosarcoma, malignant peripheral nerve sheath tumour of Schwann cell type and epithelioid sarcoma. Electronmicroscopy was of most use for the diagnosis of malignant peripheral nerve sheath tumour of perineurial cell type and marker-negative monophasic synovial sarcoma, and for confirming malignant fibrous histiocytoma. Fifteen of 19 marker-negative spindle cell tumours (79%) were diagnosable by electronmicroscopy. A combination of techniques resulted in a specific diagnosis in 193 cases (96.5%). The routine use of electronmicroscopy in sarcoma diagnosis can improve accuracy of diagnosis, establish the true frequency of marker-positivity for each ultrastructurally confirmed tumour type and minimise the number of unclassifiable cases.

Rhabdomyosarcoma in children: a histological and immunohistochemical study of 59 cases

Recent studies have suggested that rhabdomyosarcoma can be divided into favourable and unfavourable histology groups. Those subtypes comprising the unfavourable histology group are alveolar, monomorphous round cell and anaplastic rhabdomyosarcoma, with a favourable histology group of embryonal rhabdomyosarcomas. An immunohistological study was undertaken on 59 childhood rhabdomyosarcomas, using antisera to keratin, S100 protein, vimentin, desmin, myoglobin, and troponin T. Our results suggest that desmin is the single most useful antibody in the diagnosis of rhabdomyosarcoma and was expressed in all our cases. The expression of troponin T in the majority of embryonal rhabdomyosarcomas but not in the other histological types has prognostic implications.

Anaplastic Wilms' tumor and other clinically aggressive childhood renal neoplasms: ultrastructural and immunocytochemical features

The ultrastructural and immunocytochemical findings in a series of 32 rarely encountered childhood renal malignancies are reviewed. The discussion includes anaplastic Wilms' tumors, renal clear cell sarcomas, rhabdoid tumors, carcinomas, sarcomas, neuroendocrine tumors, and lymphomas. An attempt is made to assess the relative merits of these two techniques in the differential diagnosis of these often troublesome lesions.

Lectin histochemistry of experimental murine rhabdomyosarcomas

Methylcholanthrene-induced murine rhabdomyosarcomas and skeletal muscle of 10 and 18 d old murine embryos were investigated by lectin histochemistry (WGA, RCA-I, LCA, Con-A, PSA, UEA-I, PNA) and by immunohistochemistry (vimentin, desmin, myoglobulin). In rhabdomyosarcomas as well as in the developing skeletal muscle a clear trend was visible. A decrease of vimentin positivity and an increase of desmin positivity were associated with a diminution of binding sites for WGA, RCA, and LCA. No binding moieties for these lectin could be demonstrated in myoglobin positive normal and neoplastic rhabdomyomatous cells at all. The homologous expression or absence of markers reflected the cellular variability in rhabdomyosarcomas and may be explained as a phenomenon of different tumor cell maturation. The results show that rhabdomyosarcomatous cells are imitating the normal skeletal muscle development.

Rhabdomyosarcoma of the nasopharynx a case with recurrence of tumour after 20 years

A case of embryonal (botryoid) rhabdomyosarcoma of the nasopharynx originally occurring in a two year old male, with late recurrence in the neck 20 years after treatment by combined surgery and radiotherapy is presented. The histological diagnosis of rhabdomyosarcoma, and the significance of late recurrence are discussed.

Rhabdomyosarcoma with bone marrow metastasis simulating acute leukemia. Report of two cases

Rhabdomyosarcoma manifested as a systemic disease is very rare and cases showing diffuse metastasis in the bone marrow are most unusual. Recently we encountered two cases of rhabdomyosarcoma with diffuse bone marrow metastasis which were clinically manifested as acute leukemia. The first patient was a 15-year-old female, who was admitted in 1982 with pancytopenia and many large primitive cells in bone marrow aspirates, hematological malignancy being diagnosed. Thereafter the bilateral breasts showed rapid swelling and a biopsy specimen revealed the histological features of typical alveolar rhabdomyosarcoma. The primary site of the neoplasm remained undetermined during the course. At autopsy, it was disclosed that the neoplasm originated from the left thigh and showed generalized metastasis. The second patient was a 38-year-old man, who was admitted in 1986 because of a nasal polyp obstructing the nasal cavity, and persistent nasal bleeding. Peripheral blood samples showed leukoerythroblastosis and thrombocytopenia, and large primitive cells were found in bone marrow aspirates, so that hematological malignancy was initially diagnosed. A biopsy specimen of the nasal polyp showed proliferation of large round cells and electron microscopy demonstrated the ultrastructural features of rhabdomyosarcoma.

Embryonal rhabdomyosarcoma

Rhabdomyosarcoma is one of the most common malignancies of the mesenchymal tissue in the head and neck region. A case of a 26-year-old male with oral rhabdomyosarcoma is presented. The clinical and pathologic aspects of this malignancy are also reviewed. Furthermore, the histopathologic and ultrastructural features of this neoplasia are described and the important role of electron microscopy in diagnosis of the myogenic tumor is emphasized. Finally, different modes of treatment for the rhabdomyosarcoma are discussed.

Embryonal rhabdomyosarcoma: presentation as a parotid gland mass

Solid tumors occur infrequently during childhood. Rhabdomyosarcoma is the most common soft tissue sarcoma occurring in children. Therapeutic advances during the last 15 years have lead to a vast improvement in cosmetic and functional results and in overall survival. A case report of rhabdomyosarcoma of the parotid gland and a review of the literature are presented to highlight these advances.

Primary pulmonary rhabdomyosarcoma of the lung in children. Report of two cases presenting with spontaneous pneumothorax

This report describes two cases of pulmonary rhabdomyosarcoma occurring in children, ages 21 and 30 months at diagnosis. Both patients presented with spontaneous pneumothorax and had cystic changes in the affected lung by chest x-ray. Ultrastructural and immunohistochemical studies supported the myogenic phenotype of these neoplasms. The authors were unable to confirm that either of these tumors had unequivocally originated in a congenital cyst although previous authors have reported this association. An apparent morphologic spectrum of embryonic appearing neoplasms including pulmonary blastoma and a malignant mesenchymoma have been observed in the lungs of children.

Embryonal rhabdomyosarcoma in nude mice and in vitro

A transplantable tumor strain designated YNnu and a cultured cell line designated YN were established from the human paratesticular rhabdomyosarcoma of a 15-year-old boy. In vitro the cells showed ultrastructural features of immature mesenchymal cells, and a few cells were labeled by antibodies to myoglobin and/or desmin. In nude mice, the cells became to contain numerous myofibrils with Z-bands, and considerable number of cells reacted with anti-myoglobin and/or anti-desmin antibodies. We conclude that spindle-shaped or small round cells are the most immature rhabdomyoblast with multiplicity for cellular differentiation.

Extraosseous Ewing's sarcoma versus primitive rhabdomyosarcoma: diagnostic criteria and clinical correlation

A light and electron microscopic study of 51 cases of Ewing's sarcoma of bone (ESB) and 33 soft tissue sarcomas (carrying a variety of light microscopic diagnoses, including primitive rhabdomyosarcoma) in children and young adults was performed to clarify the similarities and differences among these tumors. Ultrastructural criteria were developed to evaluate the neoplasms. Remarkable ultrastructural uniformity was found in the cases of ESB. In contrast, the soft tissue sarcomas could be divided into two distinct groups on the basis of the ultrastructural criteria: those closely resembling primitive areas of otherwise differentiated rhabdomyosarcomas, and those indistinguishable from ESB. It is proposed that the diagnosis of soft tissue Ewing's sarcoma be reserved for lesions identical to ESB by both light and electron microscopy. The first group of sarcomas may be histogenetically related to rhabdomyosarcoma and should be distinguished from extraosseous Ewing's sarcoma, as their clinical behavior appears to be quite different.

Tumors of skeletal muscle

The most common tumors arising in muscle are soft tissue sarcomas, fibromatoses, and hemangiomas. Rhabdomyosarcoma is primarily a tumor of childhood and adolescence and arises most commonly in extramuscular sites. Most intramuscular rhabdomyosarcomas are alveolar. Increased diagnostic accuracy and the recognition of malignant fibrous histiocytoma have changed understanding of adult, intramuscular, pleomorphic rhabdomyosarcoma. Immunohistochemistry is playing an increasingly important role in the diagnosis of rhabdomyosarcoma, and the correlation between the histologic features and clinical behavior of rhabdomyosarcoma is under investigation. Because of their diversity and overlapping histologic features, muscle tumors are a challenge for the pathologist and require intensive study by current techniques.

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.

Rhabdomyosarcoma involving the genitourinary organs, retroperitoneum, and pelvis

We report on 17 patients with rhabdomyosarcoma of the genitourinary organs, retroperitoneal, pelvic, or perineal regions. Treatment was refused by three patients with either bladder or prostatic lesions. The remaining patients were treated with combined modality therapy. Five of 6 patients with bladder lesions are free of tumor 24 to 108 months (mean 51) after diagnosis, while one patient died 4 months postoperatively; two patients with paratesticular lesions are free of disease 3 years and 10 months following diagnosis, respectively. Of two patients with perineal lesions, one patient died, probably due to metastases 21 months after diagnosis, while another patient with local tumor recurrence was treated by reexcision with follow-up for 12 months without evidence of tumor recurrence. The worst results were obtained with the four patients with retroperitoneal pelvic lesions; one patient died 3 months after gross resection of tumor, and the other three patients deteriorated in the 4 months after diagnosis. Overall, 7 of 8 operated patients with bladder or paratesticular lesions are free of disease with follow-up for 10 to 108 months. The biological behavior of embryonal rhabdomyosarcoma, with the sex and age distribution and the management are discussed.

Cutaneous extraskeletal Ewing's sarcoma

Extraskeletal Ewing's sarcoma has been recognized as being histologically indistinguishable from Ewing's sarcoma of bone. Although the occurrence of extraosseous Ewing's sarcoma in deep soft tissues has been well described, such cutaneous lesions are rare. We report the clinical history, histopathologic findings, and results of ultrastructural study of this rare variant occurring in a 12-year-old girl. She presented with a dermal and subcutaneous tumor of the left third toe, without osseous involvement. The lesion was composed of masses of round-oval cells, with perilobular fibrosis, focal hemorrhage, ill-defined pale cytoplasm containing glycogen, and absent pericellular reticulin. Ultrastructural study showed a monotonous cell population, with focal thickening of apposing membranes, high nuclear/cytoplasmic ratio, copious intracytoplasmic glycogen, and paucity of organelles except mitochondria. We present this case along with discussion of the literature and problems concerning differential diagnosis of small cell malignancies in the skin.

Mesenchymal and muscle-specific intermediate filaments (vimentin and desmin) in relation to differentiation in childhood rhabdomyosarcomas

Twenty-one childhood rhabdomyosarcomas were divided into three groups on the basis of cytologic composition. The tumors in group P consisted entirely of primitive mesenchymal cells, whereas those in groups M and W were characterized by the additional presence of numerous round rhabdomyoblasts and strap cells, respectively. The tumors were studied for the universal mesenchymal intermediate filament vimentin, and for the muscle-specific intermediate filament desmin. Vimentin positivity, which tended to be more prominent in primitive tumor cells, was found in all tumors, whereas desmin was found especially in round rhabdomyoblasts and strap cells. Desmin-positive primitive cells were found only in groups M and W, not in group P. It was concluded that the differentiation from primitive mesenchymal cells to morphologically recognizable myogenic tumor cells is accompanied by an increase in desmin positivity and, presumably, a decrease in vimentin positivity. Moreover, the observations suggest the existence of a group of "committed" cells that are morphologically primitive, but desmin-positive. These cells might play an important role in the observed further differentiation of rhabdomyosarcomas under chemotherapy.

Immunohistochemistry of soft tissue tumours: a review

The diagnosis and classification of soft tissue sarcomas can pose difficult problems for the histopathologist. Many sarcomas are too poorly differentiated to exhibit morphological features specific enough to define their histogenesis. Using the immunoperoxidase technique with commercially available antisera as a routine adjunct to other diagnostic aids, it is possible to arrive at more accurate diagnoses on which treatment protocols can be based. In addition a better understanding of mesenchymal neoplasms and their origins can be obtained by functional immunohistochemical studies.

Small round cell neoplasms: can electron microscopy and immunohistochemical studies accurately classify them?

The answer to the question posed in the title, "Small Round Cell Neoplasms: Can Electron Microscopy and Immunohistochemical Studies Accurately Classify Them?", is obviously "yes"; but a qualified yes--generally yes, perhaps with expertise usually yes, but never just plain yes. Some cases certainly will defy the best attempts even of the most expert in the application of these "special" techniques. And embarrassing as it may be for those of us infatuated with the latest technology to admit, it is with the difficult case especially that old-fashioned technology so often must be depended upon. In his excellent recent appraisal of the role of a variety of special techniques in this application, Triche offers the following comment: "Overall, electron microscopy is probably the most universally useful of all diagnostic techniques other than light microscopy in round cell tumors." The data from our studies certainly point to the same conclusion. With each of the tumors, electron microscopy demonstrated itself to be more reliable than immunohistochemistry. Electron microscopy offers not only greater sensitivity and specificity, but also greater versatility. Immunohistochemistry allows hypothesis testing only. Electron microscopy, on the other hand, can provide answers even when the right questions are not being asked. For example, if a particular small round cell tumor under investigation happens in actuality to represent something other than the neuroblastoma which it is being considered (e.g., a granulocytic sarcoma, liposarcoma, Wilm's tumor, etc.), electron microscopy can reveal this fact, but a neuron-specific enolase stain cannot. Parenthetically, it should also be said that electron microscopy has proven particularly well suited to the examination of fine-needle aspiration specimens. The two spare many patients in our institution the need for a major operative procedure to establish a secure tissue diagnosis. Immunohistochemistry does have a role to play but it is, at least in our opinion, clearly secondary to that of electron microscopy. The concept of replacing electron microscopy with a battery of immunostains has often been advocated as an economic measure, but this argument begins quickly to lose its weight as the number stains included in the battery is increased to cover the diagnostic possibilities. Giving consideration to the capriciousness of some of these stains, there exists with this also an increasing possibility of a spurious or misinterpreted result leading to an errant diagnosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Small cell tumours in childhood: a review

The past decade has seen significant advances in the treatment of childhood malignancies accompanied by appreciable improvement in survival rates. Treatment programmes have been largely formulated to meet the specific characteristics of individual tumours, as well as being based on the extent of disease presented at diagnosis. In selecting the most appropriate treatment protocol, accurate histological categorization of resected or biopsied tumour is thus of paramount importance. In the paediatric age range in which so many tumours lack differentiation as to present as, or mimic, other small cell tumours, routine methods are often insufficient to resolve problematic histology. A wide range of special techniques is now at hand to assist the pathologist with this problem and this review is an attempt partly to rationalize the application of available methodology. Of considerable importance also is a knowledge of the behavioural characteristics of this group of tumours, their prototypic histology, as well as the range of morphological variability.

Cytologic "differentiation" in childhood rhabdomyosarcomas following polychemotherapy

The effectiveness of polychemotherapy in young patients with rhabdomyosarcomas has been well established. The morphologic alterations in the tumor tissue, however, have not been widely reported. Therefore, in a group of 15 patients from 1 to 24 years of age, specimens of tumor tissue obtained before and after polychemotherapeutic treatment were compared. No morphologic changes, other than fibrosis and necrosis, occurred in patients who initially had virtually undifferentiated tumors. When moderately or well-differentiated areas were present in the initial specimens, these areas showed proportionate increases in the follow-up specimens. Moreover, the cellular characteristics of round rhabdomyoblasts and strap cells with or without cross-striations became more distinct after treatment. However, cell types that were not present in the initial specimens were never found in follow-up specimens. It was concluded that the major role of polychemotherapy is the selective destruction of undifferentiated tumor cells; further differentiated cells are stimulated either directly or indirectly to reach their maximal inherent differentiation levels, but it does not appear that transitions from one cell type to the other occur.

An investigation of beta enolase as a histological marker of rhabdomyosarcoma

Sections from 21 tumours diagnosed as primary or metastatic rhabdomyosarcoma were stained for alpha and beta enolase. The cases were subdivided into embryonal and alveolar subtypes (38% and 62%, respectively). Positive cytoplasmic staining for alpha enolase was seen in all but one case, and cytoplasmic staining for beta enolase was seen in some cells in 18 of the 21 cases (86% of the total, 88% of the alveolar subgroup, and 85% of the embryonal subgroup). No cells stained positively for beta enolase in the control series of neuroblastomas, fibrosarcomas, Wilms' sarcomas, and an osteosarcoma. The results show that beta enolase is a sensitive marker of muscular differentiation in rhabdomyosarcoma.

Recent advances in pathology as applied to orbital biopsy. Practical considerations

Advances in pathology allow for more specific diagnoses of orbital disease. The authors discuss the value of awareness of advances in cytology, histochemistry, immunohistochemistry and electron microscopy as applied to orbital disease. Modern cytologic technique can aid in clearer visualization of cellular detail with improved diagnosis of thin needle aspiration biopsies. Histochemistry offers an increasing range of methods for identification of cellular and extracellular substances such as amyloid, fibrin, neuroglia, and collagen. Immunohistochemistry allows for identification of an ever-increasing number of component antigens including immunoglobulins, myoglobins, keratin, glial fibre protein, etc. Electronmicroscopic technique including plastic embedding allow for specific identification of lesions based on subcellular components and characteristic nuclear, cytoplasmic, membrane, basement membrane and stromal components. The value of these methods has been demonstrated with case presentations of "small round cell tumors" of the adult and child. In addition, the pathologic diagnosis of several rare lesions of the orbit including neuroendocrine carcinoma, histiocytosis X, simultaneously occurring poorly differentiated mucoepidermoid carcinoma of lacrimal gland and adenocarcinoma of the prostate are demonstrated to underline the advances in technology. Emphasis is placed on the management of biopsy material to maximize diagnostic potential.