Histology, immunohistochemistry, and electron microscopy of small round cell tumors of bone

Small round cell tumors (SRCTs) of the bone make up a family of primary bone sarcomas with morphologically, biologically, and clinically specific features. Among them, Ewing's sarcoma (ES) is the most common entity, but several varieties such as atypical ES, large cell ES, and ES with neuroectodermal differentiation (peripheral primitive neuroectodermal tumor of the bone or neuroepithelioma of the bone) have been identified recently. Histology and electron microscopy together with the variable expression of several epitopes (as shown by immunohistochemistry, mainly HBA/71 [Mic2 antigen]) provide the basis for characterizing the group within the context of neuroectodermal-derived neoplasms. A number of other ES-like tumors with small round cells, mimicking those previously described, have been characterized; Askin's tumor of the thoracopulmonary region will be considered as an ES similar to those already described, but within a particularly anatomic location. On the other hand, the presence of an endothelial appearance within a poorly differentiated neoplasm may be present in some ES-like SRCTs (atypical ES with endothelial features). The differential diagnosis with other sarcomas defined by small round to spindle cell contours might prove difficult. Particular attention must be paid to small cell osteosarcoma and mesenchymal chondrosarcoma. Likewise, "primitive sarcoma of bone" is considered in this study because it is a very rare neoplasm differing from the formerly discussed types; its pluripotentiality provides this tumor a blastemic character and a multiphenotypic expression. Malignant non-Hodgkin's lymphoma is an unusual presentation when primary to the bone, previous to any other anatomic location. Several subtypes have been considered within a histology that encompasses that seen in lymph nodes.     

The clinical role of molecular genetics in soft tissue tumor pathology

Cytogenetic and molecular analysis of soft tissue tumors has yielded a wealth of information over the past decade. Some of the genetic aberrations that have been identified appear to be fairly specific for individual tumor types. It is because of this specificity that these findings harbor the promise to become useful as diagnostic and/or prognostic markers. Technical advances that allow the application of cytogenetic and molecular techniques to archival material have been crucial in this respect. Molecular genetics has already become an integral part of the work-up of some tumors, e.g., small cell sarcomas of childhood, which demonstrate fairly characteristic translocations, often involving the Ewing's sarcoma gene. Some genetic abnormalities have become established as prognostic markers, such as the deletion of the short arm of chromosome 1 for neuroblastomas. Soft tissue tumor pathology has also benefitted from major advances in identifying genes that are critical in mesenchymal differentiation or cell cycle control. MyoD is a good example of a such a gene, that has become useful as a diagnostic tool in rhabdomyosarcomas. Beyond potential practical applications of cytogenetic and molecular analyses in the diagnosis of these tumors, we also review their impact on several philosophical concepts concerning soft tissue neoplasia.     

Trends in students'' knowledge, opinions, and experience regarding dental informatics and computer applications

OBJECTIVE: To analyze the discriminative capability of morphometric assessment of nuclear morphology in the differential diagnosis of small round blue cell tumors (SRCTs) of bone and soft tissue. STUDY DESIGN: The study material consisted of glutaraldehyde-fixed, resin-embedded, semithin sections from 119 human tumors. Nuclear area, perimeter, maximum diameter, form factors and nuclear density were measured in at least 300 nuclei per case. RESULTS: Neuroblastoma (NB) (10 cases) showed the most regular pattern. Ewing's sarcoma (ES) (35 cases); atypical Ewing's sarcoma (AEs) (15 cases) and peripheral neuroectodermal tumors (PNET) (30 cases) showed no significant differences regarding area, perimeter or form factors, but AEs showed a lower mean nuclear density that was statistically significant. Rhabdomyosarcomas (6 cases) and osteosarcomas (OS) (11 cases) were used as controls and showed several morphometric and stereometric differences with other SRCTs, whereas microcellular OSs (6 cases) shared features of SRCTs and conventional osteosarcomas. CONCLUSION: Morphometric characterization of nuclear features reveals differences between the distinct groups of SRCTs. Although overlapping occurred between all these groups at the individual case level, this study provides new support for the existence of morphologic links within the family of ES and PNET.     

Primary mesenchymal tumors of the urinary bladder. A histological and immunohistochemical study of 30 cases

The light microscopic and immunohistochemical features of 30 primary mesenchymal neoplasms of the urinary bladder are reported. Half of the cases represented smooth and striated muscle tumors (five leiomyomas, seven leiomyosarcomas including epithelioid and myxoid subtypes, one rhabdomyoma, one embryonal rhabdomyosarcoma and one alveolar rhabdomyosarcoma). One third of the tumors were of fibrohistiocytic origin (one fibrous histiocytoma and eight malignant fibrous histiocytomas including fascicular and storiform, inflammatory and pleomorphic subtypes). In addition, a malignant epithelioid schwannoma, a round cell liposarcoma, two hemangiomas and two mixed mesodermal tumors were observed. The morphology of the vesical mesenchymal tumors was identical to that of their counterparts known to occur in other sites, particularly in the soft tissue. Muscle-specific actin, alpha-1-antichymotrypsin, S-100-protein and neuron-specific enolase proved to be useful and reliable immunomarkers for differential diagnosis of poorly differentiated leio- and rhabdomyosarcomas, malignant fibrous histiocytomas and malignant schwannomas. Since some tumors coexpressed several classes of intermediate filaments, diagnostic immunocytochemistry should only be used considering a larger panel of antibodies and in close correlation with the histological and cytological features of the neoplasms.     

Ovarian small cell tumors: an electron microscopic review

Small cell tumors of the ovary are uncommon but represent an important group to recognize in the differential diagnosis of primary and metastatic ovarian neoplasms. In some cases the correct diagnosis cannot be confidently made on the basis of clinical setting, routine light microscopy, and immunohistochemistry, and electron microscopy may be supportive or definitive in establishing cell type. The cell type is often important in choosing optimal therapy and in predicting prognosis. The authors performed electron microscopy on a moderate number of ovarian small cell tumors and here describe and illustrate the diagnostic features of representative examples of various types. The ultrastructural features of the metastatic tumors, such as embryonal rhabdomyosarcoma, neuroblastoma, and melanoma, are identical to those of their respective primary tumors, are well known, and usually pose no problem in diagnosis. On the other hand, the ultrastructural features of some primary ovarian small cell tumors may present a more difficult differential diagnosis, because they have features that are subtle and/or in common. Exemplary of tumors in this category are diffuse adult granulosa cell tumor, endometrial stromal sarcoma, and small cell carcinomas of the hypercalcemic and pulmonary (oat cell) types. Distinguishing among them may be difficult but is possible, and electron microscopy may be a valuable supplement to the diagnostic information obtained from the clinical presentation, light microscopy, immunohistochemistry and, in some tumors, cytometric analysis of these neoplasms.     

Primitive peripheral neuroectodermal tumors Mayagüez Medical Center experience

Primitive neuroectodermal or neuroepithelial tumors are names used to describe neoplasias composed of undifferentiated cells resembling germinal cells of the embryonic neural tube. These tumors are small round cell malignancies of the neural crest origin arising outside the central and sympathetic nervous system. They are described as peripheral and central neuroectodermal tumors related to the original malignant cell. A great number of tumors are described under this classification in spite of the fact that there is no an universal acceptance that these small-cell neoplasms, regardless of their primary site, are derived from immature neuroectoderm tissue. Because one tumor resembles others in terms of its phenotypic expression, multiple specific studies such as clinical profile, ultrastructural, immunocytochemical, and cytogenetic features should be studied, since no single clinical or laboratory marker is by itself diagnostic. However, there is a chromosomal reciprocal translocation, t(11;22)(q24;q12), which is unique to Primitive Neuroectodermal Tumor (PNET).     

Morphology and molecular biology of malignant soft tissue sarcomas

Malignant soft tissue tumors are classified and named according to cellular differentiation and thus the non-neoplastic soft tissue they imitate. The topical WHO classification already comprises more than 140 entities and tumor subtypes, but the process of defining new tumor variants will go on. Questions of nomenclature are discussed briefly with laying special emphasis on the non-undisputed concept of malignant fibrous histiocytomas. Without doubt, this diagnosis is made too frequently by which it has become to a collective name for unclassifiable pleomorphic sarcomas. For the time being nobody is able to say whether or not the malignant fibrous histiocytoma will remain an entity. Likely, fibrosarcomas and hemangiopericytomas are defined as exclusion diagnosis, as well. The diagnosis of malignant soft tissue tumors is based on recognizing the cellular line of differentiation. This is frequently possible at light microscopic level, sometimes additional diagnostic methods are required. The most important adjunct method is immunohistochemistry. Because aberrant differentiations and unexpected immunohistochemical reactions are known the use of a panel of antibodies is necessary. In the last years soft tissue tumors has increasingly been characterized by molecular biological methods. The results are of significance for understanding sarcoma pathogenesis and may be used for diagnosis, as well. Chromosome translocations are explained and rhabdomyosarcomas are taken as example for demonstrating the diagnostic significance of molecular biological/cytogenetic findings. Molecular biology may also aid in defining the histopathologic features of an entity as shown for intraabdominal desmoplastic small cell tumors. Eventually, heterogeneity in soft tissue sarcomas is addressed and discussed in view of its importance for diagnosis, classification and therapy as well as for development of sarcoma progression.     

Chromosomal aberrations in soft tissue tumors. Relevance to diagnosis, classification, and molecular mechanisms

In recent years, significant progress has been made in identifying characteristic chromosomal rearrangements associated with several solid tumor types, notably sarcomas, a relatively rare subset of human cancer. Most sarcomas analyzed have been found to be characterized by recurrent chromosome translocations that are specific to histological types. We have reviewed published reports of chromosomal aberrations in benign and malignant soft tissue tumors and found an incidence of specific translocations in these neoplasms that ranged from 20% to 93% within histological tumor types. Identification of recurrent chromosomal abnormalities in benign tumors has resulted in a reappraisal of the general concept that benign tumors have a normal (diploid) chromosome constitution. The variety of recurrent changes present in the different tumor types attests to the cytogenetic diversity inherent in these tumors. The chromosomal rearrangements in each of the tumor types were unique and did not correspond to cancer-associated aberrations known from other solid or hematopoietic malignancies. Cytogenetics thus provides an essential adjunct to diagnostic surgical pathology in the case of malignant soft tissue tumors, which often present substantial diagnostic challenges. In addition, it represents another approach to determine the histogenetic origin of some tumors and identifies sites of gene deregulation for molecular analysis. Indeed, recent molecular analyses of several sarcoma-associated translocations have identified novel genes and novel mechanisms of their dysregulation.     

Peripheral nervous system involvement in systemic sclerosis: the median nerve as target structure

The differential diagnosis of cutaneous small round cell malignancies is a relatively uncommon but recurrent problem that usually requires adjuvant techniques including special histochemical stains, immunohistochemistry (IHC), electron microscopy (EM), and cytogenetics (CG) to arrive at a definite answer. This report describes a case of a primary cutaneous malignancy that, after workup, fulfilled the criteria of extraskeletal Ewing's family sarcoma, which was corroborated by IHC with an antibody to glycoprotein p30/32 mic2 that is highly expressed in these neoplasms. The lesions consisted of a large nodular proliferation of poorly differentiated monotonous small round cells confined to the dermis and subcutaneous tissue. The cells had high nuclear to cytoplasmic (N/C) ratios, scattered prominent nucleoli, and indistinct cytoplasm. A periodic acid-Schiff (PAS) stain with and without diastase demonstrated abundant cytoplasmic glycogen. The glycogen was confirmed with EM, which did not show neurosecretory granules, but extensive sectioning of the tissue blocks demonstrated with light microscopy a single focus with pseudorosette formation. IHC was positive for monoclonal antibody (MAb) O13 to glycoprotein p30/32 mic2 and negative for lymphoid (CD45), neural (S-100, NF, GFAP), neuroendocrine (NSE), and muscle (MSA, desmin) markers. To the best of our knowledge, this is one of few reported cases of primary cutaneous (extraskeletal/extraosseous) Ewing's sarcoma (EEWS) and the first to use IHC with MAb O13, which recognizes the cell surface glycoprotein p30/32 mic2. This case further illustrates the continuum between EEWS and primitive peripheral neuroepithelioma and supports the unifying concept that these two entities are merely subtle morphologic variants of the same malignant neoplasm, which is better designated a Ewing's family sarcoma.     

Cytological study of the puncture biopsy specimens of the Douglas' pouch for early diagnosis of ovarian tumors

The conducted studies indicated the diagnostic opportunities of a cytologic analysis of exudates and smears from the Douglas space in patients with a suspicion to ovarian tumor. Tumor cells may be present in the peritoneal cavity not only in different stages of malignant ovarian tumors, but also in secernent and proliferating cystadenomas. A correlation between the peritoneal cell content in patients with different forms of ovarian neoplasms and press-smears from the dissected surface of the removed tumors and histological sections indicated the morphological identitiy of tumor elements and enabled the determination of the cytological criteria for the differential diagnosis of ovarian tumors prior to surgical intervention.     

Poorly differentiated synovial sarcoma: immunohistochemical distinction from primitive neuroectodermal tumors and high-grade malignant peripheral nerve sheath tumors

Synovial sarcoma is a relatively common sarcoma in adults, which in its classic bimorphic form infrequently poses a diagnostic problem. Monomorphic spindled variants, as well as the less common poorly differentiated variants, may be confused with other soft-tissue sarcomas; the poorly differentiated variant (PDSS), in particular, may be histologically indistinguishable from other small, blue, round cell tumors, including primitive neuroectodermal tumors (PNETs). Detection of the synovial sarcoma-associated t(X;18) by either cytogenetic or molecular genetic approaches may be necessary to confirm the diagnosis of synovial sarcoma in difficult cases. We evaluated 10 cases of PDSS from eight patients using a panel of antibodies (including those to intermediate filament proteins, nerve-sheath associated markers, and neuronal and neuroectodermal associated markers) in order to better establish the immunophenotype of this tumor and to help distinguish it from the tumors with which it may be confused, particularly PNETs and high-grade malignant peripheral nerve sheath tumors (MPNSTs). Our results showed PDSS to have significant immunophenotypic overlap with both PNETs and MPNSTs. In most instances these three entities may be differentiated by a panel of antibodies that should include those to both low and high molecular weight cytokeratins, epithelial membrane antigen, type IV collagen, CD99, CD56, and S-100 protein. Our results also suggest that synovial sarcoma may be a tumor showing combined neuroectodermal and nerve sheath differentiation--perhaps because of translocation-associated expression of specific proteins--rather than a carcinosarcoma of soft tissues or a tumor of specialized arthrogenous mesenchyme.     

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INTRODUCTION: The neuroectodermal tumor of bone constitutes a recently isolated neoplasm, which morphologically resembles the peripheral neuroepithelioma of soft tissue. The diagnosis is made by excluding readily classified small round cell neoplasms and then demonstrating the neural origin of the tumor by means of ultrastructural or immunocytochemical studies. CLINICAL CASE: We report a case of a primary neuroectodermal tumor (PNET) with atypical findings (primary cervical location, massive vertebral body infiltration and isolated neurological symptomatology). Total tumor removal was achieved by means of a one-stage three-level laminectomy (partial C5, total C6-C7), C6 somatectomy, and combined anterior and posterior cervical spinal instrumentation and fusion. CONCLUSIONS: Our case presents three peculiar features: 1) isolated myelopathic symptomatology (first case described); 2) primary isolated massive vertebral cervical involvement with intraspinal epidural extension (first case described); 3) one-stage tumor resection, fusion and instrumentation. Since radiation therapy causes tumor shrinkage but is not curative, radical removal is mandatory even with complex instrumentation procedures.     

An immunohistochemical analysis of anti-amylase antibody reactivity in acinic cell adenocarcinoma

In many salivary acinic cell adenocarcinomas, well-differentiated serous acinar-type cells may be few and inconspicuous. In these cases it may be difficult to distinguish acinic cell adenocarcinoma from other types of salivary gland neoplasms such as cystadenocarcinoma. The usefulness of antisalivary amylase antibody immunohistochemical staining as a diagnostic aid was assessed on paraffin-embedded tissue sections from 27 typical acinic cell adenocarcinomas. Only 4 of 27 tumors showed reactivity in tumor cells. We conclude that anti-amylase antibody is of limited value in the recognition of acinic cell adenocarcinoma when light morphologic features are insufficient for diagnosis.     

Fine-needle aspiration of intra-abdominal desmoplastic small cell tumor

The cytologic features of four cases of histologically confirmed intra-abdominal desmoplastic small cell tumor (DSCT) that occurred in males between 18-27 yr of age are presented. Smears showed small cells with scant cytoplasm which were primarily arranged in loosely cohesive clusters. Nuclei were oval to round with evenly distributed, finely granular chromatin and inconspicuous nucleoli. As is typical of DSCT, the cells strongly expressed keratin and desmin in all cases. In the one case studied by electron microscopy, it was demonstrated that the cells were joined by small junctions and contained paranuclear aggregates of intermediate filaments. The absence of the characteristic desmoplastic stroma in DSCT aspirates and the nonspecific cytologic features of this small round-cell tumor (SRCT) made cytologic interpretation difficult. Cytopathologists should be aware of this entity so that DSCT is included in the differential diagnosis of SRCTs that occur in intra-abdominal sites. A panel of markers that includes keratin and desmin should be used to assist in the identification of DSCT.     

Adrenal pheochromocytoma mimicking small cell carcinoma on fine needle aspiration biopsy. A case report

BACKGROUND: Fine needle aspiration biopsy (FNAB) is a sensitive and specific technique in the diagnosis of adrenal tumors. However, in rare cases the cytomorphologic features may mimic small cell neoplasms. CASE: A 54-year-old male presented with a history of hypertension and left flank pain of recent onset. Abdominal computed tomography (CT) showed a 4-cm mass involving the left adrenal gland. Fine needle aspiration biopsy (FNAB) showed groups of small round cells with hyperchromatic nuclei. The findings were highly suspicious for metastatic small cell carcinoma. Subsequently it was learned that the mass had been noted three years earlier on CT studies but had grown from 2.5 to 4 cm. A chest radiograph was unremarkable. The clinical findings were more in keeping with a primary adrenal tumor. Immunohistochemical staining done retrospectively on the cell block showed positive reactivity for chromogranin and neuron-specific enolase. These findings, correlated with the clinical features, were in keeping with a diagnosis of pheochromocytoma. Left adrenalectomy revealed a pheochromocytoma. CONCLUSION: Adrenal pheochromocytoma should be included in the differential diagnosis of small round cell neoplasms seen on FNAB of the adrenal gland. Immunohistochemistry and clinical findings are helpful in reaching the correct diagnosis.