Appraisal of the comparative utility of immunohistochemistry and electron microscopy in the diagnosis of childhood round cell tumors

Intraoral adult rhabdomyoma: a case report

A case of adult rhabdomyoma is reported. The lesion is a rare benign tumor of skeletal muscle origin which occurs predominantly in the head and neck region. In the present case, the clinical diagnosis favored a benign salivary gland tumor. Histologically, the tumor was composed of large round, oval, and polygonal cells of varying size with abundant pale, eosinophilic, fine, granular cytoplasm with peripherally located nuclei. Immunohistochemically, the lesion was positive for muscle-specific actin, smooth muscle actin, desmin, S100 protein, and Masson's trichrome. Electron microscopic examination confirmed the presence of numerous myofibrils. The lesion was treated by surgical resection. The clinical, histological, immunohistochemical, and ultrastructural features are discussed in this study.

Detection of EWS/FLI-1 by Immunostaining. An Adjunctive Tool in Diagnosis of Ewing's Sarcoma and Primitive Neuroectodermal Tumour on Cytological Samples and Paraffin-Embedded Archival Material

Purpose. Recently we showed that the 68-kDa fusion protein derived from the EWS/FLI1 hybrid gene can be specifically detected by Western blotting using a polyclonal antibody to the C-terminal of FLI1 on biopsy material from Ewing's sarcoma. The aim of this study was to investigate whether this antibody also could be used for immunocytochemistry and immunohistochemistry in diagnosis of Ewing's sarcoma.

Methods. Immunostaining on paraffin-embedded archival material, fine-needle aspirates and tumour touch imprints from Ewing's sarcomas and primitive neuroectodermal tumours (PNET) for detection of the fusion protein was performed. Most cases were also analysed by Western blotting.Tumours of differential diagnostic importance were also included.

Results. Eighty per cent (12/15 cases) of the Ewing tumours exhibited a positive immunoreactivity for the FLI1 antibody. The signal was mainly localised in the nuclei of the tumour cells, which seems reasonable since EWS/FLI1 is a transcription factor. The signal was found to be specific since it did not appear when the blocking peptide was added to the antibody solution.Moreover, two other types of small-round cell tumours (i.e. neuroblastoma and alveolar rhabdomyosarcoma) were negative as well as most normal tissues.

Discussion. Immunostaining of histological and cytological specimens with the FLI1 antibody can be of diagnostic relevance in Ewing tumours carrying t(11;22).The absence of immunoreactivity in non-Ewing cells is most likely due to a low expression of the wild-type FLI1 protein.

Immunohistochemistry of primary malignant neuroepithelial tumors of the kidney: a potential source of confusion?

Ewing sarcoma/peripheral primitive neuroectodermal tumor (pPNET) is a rare primary tumor of the kidney with morphologic features similar to those of other primitive tumors. Previous studies have shown that these tumors frequently stain positively with immunostains against CD99 and FLI-1 and negatively with stains against WT-1, suggesting that these markers may be used for the distinction between Wilms tumor and pPNET. We present 30 cases of primary malignant neuroepithelial tumor with immunohistochemical profiles and reverse transcriptase polymerase chain reaction (RT-PCR) analysis and show that immunophenotypic overlap exists between Wilms tumor and pPNET. A subset of 30 neuroepithelial tumors from the National Wilms Tumor Study originally categorized as putative pPNETs of the kidney was stained with FLI-1, WT-1, and thyroid transcription factor-1. Bicolor fluorescence in situ hybridization studies were performed on 19 of the cases. Other data on these tumors were available from a previous study (Am J Surg Pathol 2001;25:133). Of 7 primary tumors that had the EWS/FLI-1 fusion transcript by RT-PCR, 6 exhibited strong immunopositivity for FLI-1. Nine that were negative by RT-PCR stained positively with the FLI-1 stain. Five fusion-negative cases stained with both FLI-1 and WT-1. Three fusion-negative cases were negative for FLI-1 but positive for WT-1. Five fusion-negative cases were negative for both FLI-1 and WT-1. Of the 30 cases, 29 were positive for CD99. Seven cases that were negative for the EWS-FLI-1 fusion by RT-PCR were positive by fluorescence in situ hybridization. All cases were negative for thyroid transcription factor-1. Reliance upon immunohistochemistry as the sole means of ancillary diagnosis in renal pPNET can lead to confusing results. We recommend molecular fusion studies for clarification of primitive renal tumors with unexpected immunophenotypic results.

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

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.

Rhabdomyosarcoma of the head and neck in children

OBJECTIVE

The purpose of this study was to determine the rhabdomyosarcoma types involving the head and neck (H&N) region in children and their immunophenotype.

DESIGN

Anatomic pathology archives at Texas Children's Hospital were searched for all rhabdomyosarcoma cases over a 20-year period. One-hundred and thirty-seven cases were identified, with 50 being H&N cases. The cases were typed according to the Intergroup Rhabdomyosarcoma Study (IRS) criteria. Immunocytochemistry for myogenic and non-myogenic markers was performed on all H&N cases. Electron micrographs from cases (n=32) where ultrastructural examination had been performed at the time of original diagnosis were reviewed.

RESULTS

Children with H&N rhabdomyosarcomas had a mean age of 5.3 years (median 4 years). There was a male predilection (1.7M:1.0F). Primary tumor sites were: face NOS (18%), orbit/periorbital (16%), nasal cavity/nose (14%), lymph nodes (12%), paranasal sinuses (10%), parameningeal (10%), parotid gland (6%), neck (6%), infratemporal fossa/zygoma (2%), buccal mucosa (2%), palate (2%), and larynx (2%). Metastatic disease at diagnosis (33% of all cases) occurred in the bone marrow (11%), cerebrospinal fluid (6%), peritoneal fluid (6%), lung (4%), parietal pleura (2%), pleural fluid (2%) and pericardial fluid (2%). Rhabdomyosarcoma types (IRS criteria) were: embryonal (60%), alveolar (classic and solid subtypes, 28%), botryoid (4%), undifferentiated (4%), spindle cell (2%) and anaplastic (2%). Immunocytochemical findings were: polyclonal desmin (96%); myogenin (96%); muscle-specific actin (74%), smooth muscle actin (12%). Nonmyogenic markers included: vimentin (100%), CD99 (16%), p53 (16%), pancytokeratin (10%), NSE (8%), LCA (6%), CD20 (6%), EMA (2%), and NB-84 (0%, neuroblastoma). Undifferentiated sarcoma expressed only vimentin. By ultrastructural examination, 44% had readily identified z-bands and myofilaments, 37% had infrequent to rare myofilaments and z-bands, and 19% had myotubular intermediate filaments.

CONCLUSIONS

Distribution of H&N rhabdomyosarcoma IRS types is similar to that for all primary sites, with the exception that embryonal types are modestly increased while alveolar type is mildly decreased. There are many non-myogenic immunocytochemical markers that cross-react with rhabdomyosarcoma. Differentiation between favorable and unfavorable rhabdomyosarcoma types is important for appropriate therapy, and predicting prognosis and survival.

Immunoelectron microscopy in the age of molecular pathology

The introduction of molecular biology-based diagnostic procedures in pathology has created substantial expectations in regard to screening, characterization, monitoring, and detection of predisposition to a variety of diseases, most notably malignant neoplasms. It should be emphasized, however, that molecular studies are only one component of the diagnostic process and that more traditional methods are still required in the evaluation of tumors and management of patients. The data obtained from the molecular biology-based studies must be always interpreted in conjunction with the clinical history, immunomorphologic findings, and other pertinent ancillary data. Routine evaluation of tissues using traditional light microscopy remains the backbone of pathologic evaluation. The additive role of molecular diagnostics often depends on how accurate the initial evaluation has been. Ancillary techniques such as immunohistochemistry and electron microscopy remain essential in properly characterizing diseased tissues and in speciation of tumors. Ultrastructural immunolabeling capitalizes on combining these two techniques and providing exquisite immunomorphologic evaluation. The extra time and effort required are more than compensated by the degree of sophistication that can be achieved when this diagnostic technique is utilized and the added expense is rather reasonable. The value of molecular biology-based diagnostics is potentially questionable if the tissue samples are not initially accurately characterized. The question that molecular diagnostics may be trying to answer may be the wrong one or the answer obtained may be interpreted incorrectly if the context of the clinicopathologic situation has not been clearly defined using traditional diagnostic techniques.

Differentiation, histogenesis and morphogenesis: their implications for tumor diagnosis

Differentiation, as employed in tumor classification for histopathology, refers to the resemblance of neoplastic cells to their presumed cell/tissue of origin. Since differentiation for diagnosis is obtained by analysing histological images, this histogenetic concept creates practical limitations. Morphogenesis, a variant of differentiation, is a wider concept since it takes into consideration the nature of the tumor cells, their organization and their synthetic products. Consequently, morphogenesis, rather than differentiation, seems to be a better predictor of histogenesis in tumor diagnosis.

Electron microscopy in tumour diagnosis: continuing to complement other diagnostic techniques

The histopathological diagnosis of tumours has been transformed by immunohistochemistry. Used with experience and judgement, a panel of antibodies or antisera, combined when necessary with antigen retrieval, will enable the accurate typing of most problematic tumours. This has led many histopathologists to question whether the electron microscope has any residual utility for tumour diagnosis; the machines are large, costly to purchase and maintain, and will accept only minute samples of tissue. The following articles by Mierau and by Eyden, both strong advocates, comment on the current and future role of electron microscopy in tumour diagnosis.

Electron microscopy for tumour diagnosis: is it redundant?

The histopathological diagnosis of tumours has been transformed by immunohistochemistry. Used with experience and judgement, a panel of antibodies or antisera, combined when necessary with antigen retrieval, will enable the accurate typing of most problematic tumours. This has led many histopathologists to question whether the electron microscope has any residual utility for tumour diagnosis; the machines are large, costly to purchase and maintain, and will accept only minute samples of tissue. The following articles by Mierau and by Eyden, both strong advocates, comment on the current and future role of electron microscopy in tumour diagnosis.

Role of electron microscopy in the evaluation of soft tissue neoplasms, with emphasis on spindle cell and pleomorphic tumors

The current significant role of transmission electron microscopy in the evaluation of soft tissue tumors when correlated with conventional histological and immunohistochemical studies is discussed for the following entities: myxofibrosarcoma, storiform-pleomorphic fibrosarcoma (malignant fibrous histiocytoma), and myofibrosarcoma; dermatofibrosarcoma protuberans; hemangiopericytoma; monophasic synovial sarcoma; extrarenal rhabdoid tumor; soft tissue perineurioma; and gastrointestinal stromal tumors, notably the so-called autonomic nerve variant.

Role of electron microscopy and other special techniques in the diagnosis of childhood round cell tumors

A series of case presentations show unique challenges associated with childhood round cell tumors and the role of ancillary techniques in diagnosis. Electron microscopy is shown to be the most powerful individual technique. Immunohistochemistry is less effective but also essential. Other ancillary techniques may provide needed additional diagnostic information. Because this is an area where it is of great importance to secure the most rapid, accurate, and specific diagnosis possible, an integrated multimodal approach is recommended--incorporating light microscopic, electron microscopic, and immunohistochemical studies as a matter of routine, and providing for cytogenetic and/or molecular diagnostic studies as indicated.

Value of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumors

Light microscopy alone is often insufficient to type a soft tissue tumor. In this study 142 consecutive soft tissue tumors (benign or malignant), for which both electron microscopy (EM) and immunohistochemistry (IHC) had been performed, were reviewed to assess the contribution of these two modalities to making the final diagnosis. A tentative diagnosis (58 cases) or differential diagnosis (84 cases) was made following light microscopical examination. Ultrastructural and immunohistochemical features were then reviewed. Overall, EM more often contributed to diagnosing the tumor type than IHC (80 vs. 65%), with a statistically significant difference (p = .001). This was most apparent in high-grade sarcomas (grade III); the contribution of the two modalities was similar in benign and low-grade malignant tumors. IHC more often than EM (33% vs 22%) did not provide information to aid in typing of the tumor. However in 47% of the cases in which one of the two modalities was noncontributory, the other technique was helpful in reaching a diagnosis. These findings suggest that both IHC and EM are necessary to properly evaluate soft tissue tumors.