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.

A series of fine‐needle aspiration biopsies (FNAB) from 76 children with round cell malignant tumors was studied by both light and electron microscopy. In 14 cases the material submitted for electron microscopy was inadequate, whereas in the remaining 62 biopsies a definitive diagnosis could be made. These included 29 malignant lymphomas, 8 neuroblastomas, 12 Ewing's sarcomas, 3 metastatic retinoblastomas, 3 Wilms' tumors, 3 rhabdomyosarcomas, and 4 unclassified tumors. The results from this study indicate that FNAB studied by light and electron microscopy can be effective in diagnosing small cell tumors in children.

A case study of desmoplastic small round cell tumor with divergent differentiation in a 13-yr-old boy is presented. Clinical, cytologic, histologic, immunohistochemical, and ultrastructural findings are reported. There was a close correlation between the various histologic and cytologic patterns. Immunohistochemical studies revealed strong positivity of many of the tumor cells for cytokeratin, vimentin, and desmin. Ultrastructurally, some of the tumor cells contained aggregates of cytoplasmic intermediate filaments. Fine-needle aspiration biopsy may suggest the diagnosis of desmoplastic small round cell tumor. Confirmation of the diagnosis may be provided by immunohistochemistry and electromicroscopy.

Fine-needle aspiration biopsies from five patients with endodermal sinus tumors (ESTs) were reviewed, and the findings were correlated with histologic and ultrastructural appearances. In the aspiration smears, two types of tumor cells were seen, forming clusters of variable sizes. Type A cells had distinct cell borders, and their cytoplasm contained only occasional vacuoles. Type B cells had ill-defined cell borders and formed syncytial clusters; their cytoplasm was characterized by large numbers of rounded vacuoles. The background contained patches of mucoid material and macrophages with foamy cytoplasm. Eosinophilic hyaline cytoplasmic bodies and irregular deposits of intercellular basement membrane-like material were recognized easily in aspiration smears. These features correlated well with histologic and ultrastructural appearances. The significance of these findings in the fine-needle aspiration biopsy diagnosis of EST and its distinction from other germ-cell and non-germ-cell tumors is discussed.

A series of 14 fine-needle aspiration biopsies (FNAB) from histologically proven cases of histiocytosis-x (Hx) were reviewed. The smears revealed a variable mixture of Langerhans cells, eosinophils, macrophages, polymorphonuclear cells, and giant cells. Based on the predominant cells present, the cases were further categorized as Langerhans cell predominant (nine cases), eosinophil predominant (two cases), and macrophage predominant (three cases). Langerhans cells were usually polygonal without significant evidence of phagocytosis and frequently contained indented nuclei. In three cases, several Langerhans cells showed prominent dendritic processes. Electron microscopy in 10 cases revealed Langerhans cells with varying degrees of morphologic differentiation. All cases studied revealed Birbeck granules. These findings indicate that FNAB may be an effective technique for diagnosing Hx.

A series of six fine-needle aspiration biopsies from three patients with malignant rhabdoid tumor of the kidney is reviewed. The smears revealed round, polygonal, and irregularly shaped cells with large nuclei and prominent nucleoli. Some of the tumor cells contained light pink to purple cytoplasmic inclusions that correlated with the eosinophilic inclusions seen in histopathologic sections and filamentous cytoplasmic aggregates noted on ultrastructural examination. Diagnosis of malignant rhabdoid tumor of the kidney may be suggested from aspiration biopsy smears; however, further confirmation of the diagnosis by histologic or ultrastructural examination is desirable.

A series of fine-needle aspiration biopsies performed in 635 children were reviewed. The diagnoses rendered in these patients included malignant lymphoma in 139 (21.9%); Hodgkin's disease, 25 (3.9%); neuroblastoma, 58 (9.1%); Wilms' Tumor, 37 (5.8%); Ewing's sarcoma, 32 (5.0%); rhabdomyosarcoma, 25 (3.9%); retinoblastoma, 22 (3.5%); leukemia infiltrate, 33 (5.2%); and miscellaneous tumors, 52 (8.2%). In 171 patients (26.9%), the biopsy was nondiagnostic. The cytomorphological characteristics of these lesions are briefly described and illustrated. Salient morphological features are further correlated with histological and ultrastructural appearances. Immunocytochemical patterns of these tumors are also discussed briefly.

Aspiration smears from a series of 21 papillary thyroid carcinomas were studied and a number of morphologic features correlated with the histologic and ultrastructural patterns. These included types of papillary structures, metaplastic cells, grooved and lobulated nuclei, optically clear nuclei, intranuclear inclusions, and macrophages. Generally there was a close correlation between histologic and cytologic findings. The numbers of macrophages and metaplastic cells appeared to be exaggerated in aspiration smears as compared with those seen on histologic sections. Optically clear nuclei were not seen on the air-dried cytologic smears. Grooved nuclei were somewhat difficult to recognize in the aspiration smears, although lobulated nuclei were identified easily. We consider the latter to be a significant feature in the diagnosis of papillary carcinoma. Ultrastructurally grooved nuclei showed a deep linear indentation of the nuclear membranes. Lobulated nuclei were characterized by multiple indentations that divided the nucleus into several lobules.