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The clinico-pathologic characteristics of 10 resected pulmonary tumors, which proved to be well-differentiated neuroendocrine carcinomas (WDNC) on the basis of light microscopic, immunocytochemical, ultrastructural and immunoelectron microscopic investigations, were evaluated. The tumors showed a wide spectrum of histologic features that could be referred to three basic patterns: 1) a carcinoid-like pattern; 2) an organoid pattern characterized by palisading cells at the edge of cellular areas, and 3) a prevalent adenocarcinoma-like pattern. The second pattern was the most distinct even though it often mimicked the small cell/large cell subtype of small cell carcinoma (SCC) owing to its association with marked atypia and poor differentiation. All but one of the patients were males and smokers. The mean age was 58 years. Half of the tumors were centrally located including those showing the adenocarcinoma-like pattern. Disease-free and overall survival and type of tumor dissemination in four patients were similar to those of SCC. Five evaluable patients were alive and disease-free after a mean follow-up of 74 months. Two of these were initially diagnosed as SCC. We conclude that, because of its impact on prognosis, the diagnosis of WDNC appears to be relevant although other factors able to adversely affect the clinical course remain undefined.

The authors report a case of primary mucoepidermoid carcinoma of the liver in a 66-year-old woman. Electron microscopy findings suggest an origin from the biliary epithelium as well as cholangiocarcinoma, which clinical and prognostic features are similar to those of mucoepidermoid carcinoma.

Inflammatory pseudotumor of the liver is a very rare lesion. Herein we describe two cases of this entity which occurred in two women aged 22 and 49 years, respectively. Both cases were considered to be clinically malignant and only the histopathologic examination revealed the non-neoplastic nature of the disease. Ultrastructural and immunohistochemical studies further supported the evidence of a reactive disease.

Light and electron microscopy study of an unusual primary liver neoplasm observed in a 36-year-old woman. By light microscopy the tumor, initially detected by a needle biopsy and later surgically removed, was mainly composed of spindle-shaped and multinucleated cells which were similar to rhabdomyoblasts. These cells, however, showed ultrastructural features of hepatocytes.

We report a case of ileal carcinoid which clinically presented as a primary breast carcinoma. Review of the literature demonstrated only 9 cases of carcinoids metastatic to the breast. In spite of the rarity of this event, the differential diagnosis between primary and metastatic carcinoid of the breast should be considered in view of the different clinical management of these two settings.

We report on an intravascular bronchioloalveolar tumor (IVBAT) detected in the lungs of a 45-year-old female. The results of the immunohistochemical and ultrastructural investigations stress the already suggested endothelial origin of the tumor. The clinical and histopathologic differential diagnoses between IVBAT and other rare tumors of the lung are discussed. Similarities of IVBAT with other more or less recently described endothelial tumors of the liver, skin and soft tissues are pointed out.

A nephroblastoma (Wilms' tumor) with morphological, histochemical, immunohistochemical and ultrastructural evidence of neuroendocrine differentiation is described. Whereas areas of neural differentiation and occasional argyrophilic cells in cases of Wilms' tumor have been previously reported, the unique characteristic in this case was the extent of the neuroendocrine differentiation, as shown by a strong Grimelius stain of over 90% of the blastematous cells. Immunoperoxidase studies employing antibodies to neuron-specific enolase and ultrastructural data were also in favor of the neuroendocrine differentiation and suggested the existence, in addition to the already reported variant of Wilms' tumor with neural differentiation, of a neuroendocrine variant which may be part of the histologic spectrum of this neoplasm.

We describe two cases of fibrolamellar hepatocellular carcinoma of the liver in two young women. Both patients presented with diffuse intra-abdominal metastases; nevertheless they had a survival of 28 and 32 months, respectively, which sustains the better prognosis of this neoplasm. Electron microscopy of one case confirmed the oncocytic features of the neoplastic cells and showed intra- and intercellular duct-like vacuoles with numerous microvilli containing a microfilament core that terminated in a terminal web, which represents an unusual aspect in the spectrum of differentiation of fibrolamellar hepatocellular carcinoma.

Spindle-cell hepatocellular carcinoma is an unusual morphologic variant of hepatocellular carcinoma with a typical sarcomatous appearance. The exact diagnosis of this tumor may be difficult when only small biopsies are available and in the absence of ultrastructural studies. We describe two cases of hepatocellular carcinoma: one was entirely composed of spindle-shaped cells, and the other was a typical hepatocellular carcinoma with only a small area of sarcomatous, fusiform cells. In the first case, ultrastructural studies demonstrated desmosomes and many Mallory bodies and confirmed the epithelial nature of the neoplasm. In the second case, no ultrastructural studies were available, but the presence of gradual transition from liver cell carcinoma to spindle-cell carcinoma excluded the diagnosis of carcino-sarcoma.

The investigation was carried out on blood smears, bone marrow aspirates, one lymph node biopsy, and the surgically removed spleen of a 53-year-old man with hairy cell leukemia. In the blood smears stained with May-Grünwald-Giemsa, 60 to 70% of the hairy cells contained tubular inclusions that corresponded to the ribosome-lamella complexes demonstrated at electron microscopy. In blood smears, imprints and cryostatic sections of the lymph node and of the spleen, hairy cells revealed tartrate-resistant acid phosphatase, beta-glucuronidase and adenosine-triphosphatase activity. In the spleen neutral esterase and alkaline phosphatase demonstrated the numerical increase of the histiocytes, which ultrastructurally displayed phagocytic activity. The presence in the spleen of pseudosinuses lined by hairy cells was confirmed by electron microscopy as well as by cytoenzymology.

Osteogenic sarcoma with marked cellular anaplasia and little or no osteoid formation may present major problems in histologic identification. The application of electron microscopy is demonstrated in a case of a poorly differentiated osteosarcoma of the tibia. Unequivocal electron microscopic diagnostic findings are described in relation to light microscopic data.

We reviewed the pathologic and clinical features of 7 cases of clear-cell hepatocellular carcinomas. Tumor cells had a typical clear, empty cytoplasm due to prominent accumulation of glycogen and lipid droplets, as demonstrated by ultrastructural study in one of our cases. Follow-up of the 7 patients did not confirm the better prognosis of this tumor reported by other investigators. The clinical course of our cases was more unfavorable than that of the other 130 cases of usual hepatocellular carcinomas treated at this Institute.

A case is reported of the simultaneous occurrence of a squamous cell carcinoma and a small cell carcinoma, both centrally located, in the right upper lobe and a peripheral adenocarcinoma in the right lower lobe. The simultaneous occurrence of three primary lung carcinomas is discussed in the light of a probable common cell origin.

A soft tissue malignant fibrous histiocytoma was studied by light and electron microscopy. The presence of fibroblast-like cells, histiocyte-like cells, undifferentiated stem cells, and xanthomatous cells was confirmed. Fibroblast- and histiocyte-like multinucleated giant cells were also observed. The observation of lysosomes in some fibroblast-like cells, the features of undifferentiated stem cells, and the presence of cells and intermediate characteristics common to xanthomatous, histiocytic, and stem cells suggest a strict relationship among these cellular types.

A retrospective survey of all electron microscopic (EM) examinations of surgical pathology specimens obtained at the Istituto Nazionale Tumori of Milan over a 5-year period (1981-1985) was carried out. During this time a total of 259 cases were examined: for 97 (38%) electron microscopy provided a substantial diagnostic contribution, whereas in 151 (58%) it confirmed the previous light microscopic diagnosis. In our experience, EM was most useful for diagnosing selected cases of cutaneous malignant melanoma predominantly metastatic, rhabdomyosarcoma, neuroblastoma and poorly differentiated neuroepithelial tumors and less helpful in the further analysis of cases of malignant mesothelioma, Ewing's sarcoma, leiomyosarcoma and fibrohistiocytic malignancies. In cases of well-differentiated neuroepithelial tumors, such as carcinoids, EM data was essentially confirmatory of (immuno)-histochemical findings.