The authors assessed a panel of immunohistochemical stains against 109 pediatric solid tumors, primarily rhabdomyosarcomas, under the auspices of the Intergroup Rhabdomyosarcoma Study. Fresh tumor tissue received from participating organizations was divided into portions that were either frozen or fixed in formalin, alcohol, or B5. Immunostaining was performed by the avidin-biotin complex method using monoclonal antibodies to desmin, neurofilaments, vimentin, cytokeratin, and leukocyte common antigen on cryostat sections. Tissue was also embedded in paraffin and stained with antimuscle-specific actin (MSA) and polyclonal antibodies to desmin, creatine kinase M subunit (CKM), myoglobin, and neuron-specific enolase (NSE). Antidesmin staining of cryostat sections was the most sensitive indicator of rhabdomyosarcoma (58 of 62 specimens positive). Results with this reagent in alcohol-fixed and formalin-fixed tissue were similar (46 of 56 positive versus 43 of 56 positive, respectively) and comparable with results with anti-MSA in formalin-fixed tissue (43 of 55 positive). However, the proportion of cells stained by antidesmin was higher in alcohol-fixed tissue than in formalin-fixed tissue. Staining with antimyoglobin and anti-CKM was much less satisfactory, with positivity rates of 17 of 37 and 11 of 57, respectively, in formalin-fixed rhabdomyosarcomas. Immunostaining of muscle markers revealed evidence of myogenesis in six undifferentiated sarcomas and in two sarcomas with inadequate histologic study on hematoxylin-eosin-stained sections. However, positivity was also noticed in samples of fibromatosis, Wilms' tumor, ectomesenchyoma, peripheral primitive neuroectodermal tumor, renal rhabdoid tumor, myositis ossificans, malignant fibrous histiocytoma, and embryonal sarcoma of the liver. The authors conclude that combined use of antidesmin and anti-MSA enhances the diagnosis of childhood sarcomas, especially when employed with other techniques such as electron microscopic study.
To correlate the histologic subtype of diffuse large cell (DLC) lymphoma with immunophenotype, clinical features, and treatment outcome, 88 consecutively diagnosed children with this disease were studied. Of these cases, 42 (48%) were immunoblastic (IB), polymorphous subtype; 17 (19%) IB, plasmacytoid; 8 (9%) IB, clear cell; 6 (7%) IB, not otherwise specified; and 15 (17%) DLC-follicular center cell (DLC-FCC) type. Of 34 cases successfully phenotyped from paraffin sections, 13 were T cell and 9 were B cell; of the remaining cases, 8 were suggestive of T-cell lineage, 3 of B-cell lineage, and 1 of histiocytic differentiation. Although histologic subtype did not correlate with clinical features or outcome, it did correlate with immunophenotype among those cases for which lineage could be unequivocally assigned (5 of 18 IB vs. 4 of 4 DLC cases were B cell; P = 0.02) Immunophenotype was also correlated with stage of disease (11 of 13 T-cell vs. 3 of 9 B-cell cases had stage III-IV disease; P = 0.03). (Stage III includes all primary thoracic tumors; stage IV includes all with central nervous system and/or bone marrow involvement.) Significant prognostic features were clinical stage and era (thus type) of therapy (P less than 0.001). The authors conclude that most cases of large cell non-Hodgkin's lymphoma in children are of IB morphologic type, most frequently of T-cell lineage, and those with T-cell phenotype appeared to have more advanced disease.
Immunodiagnosis utilizing immunohistochemical techniques is currently the most commonly utilized and readily available method of ancillary diagnosis in pediatric oncopathology. The methodology comprises relatively simple steps, based on straightforward biologic concepts, and the reagents used are generally well characterized and widely used. The principle of cancer immunodiagnosis is based on the determination of neoplastic lineage using detection of proteins typical of cell differentiation pathways. Methodology sensitivity varies and has become greater with each new generation of tests, but technical draw-backs should be considered to avoid excessive background or nonspecific results. Automated instrumentation offers a degree of accuracy and reproducibility not easily attainable by manual methods.
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