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To clarify the cellular differentiation features and facilitate diagnosis of angiomatoid (malignant) fibrous histiocytoma (AFH), four cases of AFH were examined by clinicopathologic, immunohistochemical and ultrastructural analyses. The age of the patients ranged from 10 to 24 years (mean, 17 years) and the sex distribution was equal. All cases were of subcutaneous origin: three arose in the trunk and one in the upper extremity. All patients presented with systemic symptoms, including inflammatory signs and anemia. After a mean follow up of 11 years 3 months, all patients were alive and well, although one patient twice developed local recurrence after surgery. All cases presented as multinodular, cystic and hemorrhagic tumors ranging in size from 4 to 11 cm (mean, 8 cm) and were characterized by sheets of bland spindle or round cells with oval nuclei within a circumscribed nodule often surrounded by a lymphocytic cuff. One tumor showed predominantly round cell morphology similar to Ewing's sarcoma/primitive neuroectodermal tumor. All cases (100%) exhibited immunoreactivity for vimentin, desmin, CD68 and CD57 (Leu-7). Three cases (75%) were positive for synaptophysin, and reactivity for alpha-smooth muscle actin, epithelial membrane antigen, neuron-specific enolase and CD99 (O-13) was present in two cases (50%) each. The three cases examined by electron microscopy had a mixture of fibrohistiocytic, myofibroblastic and undifferentiated cells containing cytoplasmic processes and dense-core granules. It is important for accurate diagnosis of this peculiar soft-tissue tumor to recognize that it has a variety of immunophenotypes, such as histiocytic, myofibroblastic, epithelial and neural, and may occasionally have a predominantly round cell morphology.

Malignant fibrous histiocytoma (MFH) of the gastrointestinal tract is extremely rare. Here we report a case of MFH of the cecum and review other cases of large bowel MFH in the literature. A 64-year-old man had a large tumor mass in the cecum associated with multiple small peritoneal implants. Histologically, most of the lesion showed inflammatory pseudotumor-like appearance; that is, a mixed proliferation of fibroblasts and myofibroblasts loosely arranged in sweeping fascicles or whorled structures and an admixture of chronic inflammatory cell infiltrate. The myofibroblastic nature of the spindle-shaped cells was confirmed by their immunohistochemical and ultrastructural findings. In addition, there was atypical histiocytic cells infiltrate in some areas and marked lymphatic involvement and lymph node metastasis by such histiocytic cells. These features were interpreted as MFH, although it had to be distinguished from inflammatory fibrosarcoma and leiomyosarcoma. The differential diagnosis is discussed here.

A rare case of dedifferentiated liposarcoma (well-differentiated liposarcoma with an inflammatory malignant fibrous histiocytoma (MFH)-like anaplastic component) occurring in a 69-year-old male is presented. The patient had noticed a dull pain in his left loin and thigh for about 1 month. Computed tomography examination revealed a low-density mass lesion, measuring about 6 cm in diameter, in the left iliopsoas muscle, and it was surgically removed. Grossly, the lesion was composed of an encapsulated, soft, whitish mass and an adjacent, well-demarcated, yellowish hard nodule, measuring about 2.5 cm in diameter. Microscopically, both lesions showed features of an inflammatory variant of MFH and a sclerosing type of well-differentiated liposarcoma, respectively. To our knowledge, only two cases of dedifferentiated liposarcoma combined with inflammatory MFH as a dedifferentiated component have been recorded in the literature. The salient feature of the present case is a systemic inflammatory reaction, as shown by prominent leukocytosis (up to 73,900/mm3) and the elevated serum value of C reactive protein (up to 26.0 mg/dL), which were transiently reduced after surgery. The inflammatory reaction was suggested to be induced by cytokines, such as granulocyte colony-stimulating factor and interleukin-6, which were probably produced by the tumor cells in the present case, because the elevated serum values of those cytokines were decreased after surgery.

A 78-year-old man presented with an esophageal polyp that was confirmed by immunohistochemistry and electron microscopy to be malignant fibrous histiocytoma. The tumor was comprised of a proliferation of spindle-shaped cells admixed with bizarre giant cells. These tumor cells were immunoreactive for smooth muscle actin, vimentin, alpha-1-anti-chymotrypsin and CD68. Electron microscopic examination revealed the myofibroblastic and histiocytic features of the tumor cells. No elements of epithelial or myogenic differentiation were found in the tumor. Malignant fibrous histiocytoma of the esophagus is extremely rare, with 10 cases being documented so far in the literature. The differential diagnosis of pleomorphic tumors of the esophagus is discussed.

The distribution of S-100 protein in normal tissue has been studied extensively. However, little is known about its expression in pathologic states. The aim of the present study was to investigate the expression of S-100 protein in diseased human liver, especially in Kupffer cells. One hundred cases of autopsy livers originating from patients with various diseases were examined. Increased S-100-immunoreactivity of Kupffer cells was observed in six cases. Of the six cases, four were derived from a lymphohematologic malignancy, such as B cell lymphoma, B cell lymphoblastic leukemia, multiple myeloma and chronic myelogenous leukemia with lymphoblastic crisis. Lymphohematologic malignancy accounted for 16 out of the 100 cases examined. Thus, increased S-100-positive Kupffer cells was significantly associated with lymphohematologic malignancy (P < 0.01); 25% (4/16) in cases with lymphohematologic malignancy versus 2.4% (2/84) in the remaining cases. Moreover, some of these S-100-positive Kupffer cells were positive for S-100 beta-subunit, which is not normally expressed by Kupffer cells. Although the reason for this increased S-100-immunoreactivity is speculative, the authors' hypothesis is that tumor cells may produce some factor(s) that induce the expression of S-100 protein in Kupffer cells.

A case is presented of a female infant with an atypical histiocytoma. A gradually enlarging brown lesion was noted on the left side of the chest at the age of 2 weeks. Microscopic study of a biopsy revealed an ill-defined infiltration of spindle cells with indented nuclei. The tumor cells were positive for CD14, HLA-DR, lysozyme, alpha-1-antitrypsin and alpha-1-antichymotrypsin, and negative for CD1, CD3, CD8, CD10, CD19, CD68 and S-100 by immunohistochemistry. Electron microscopy demonstrated no distinct Birbeck's granules, but aberrant granules were seen in a small number of cells. At 7 months of age, a nodule with similar histologic features was noted in the nuchal region, but was incompletely resected. The patient remains recurrence-free at 36 months of age. This case is thought to be a benign form of non-X histiocytoma.

Right-sided cardiac malignant fibrous histiocytoma (MFH) is extremely rare, and to the authors' knowledge only three cases have been reported. In this study, a case of MFH in the right ventricle, the septum, and the pulmonary valves and artery in a 47 year old male is described. The tumor showed typical pathological features of MFH, such as cellular pleomorphism, storiform pattern and abundant mitoses. Immunohistochemical and electron microscopical findings were compatible with MFH, and excluded the possibility of leiomyosarcoma and angiosarcoma. Whole body examination, including Gallium scintigram, localized the primary site to the heart. The details of this case are presented with a review of the reported cases of cardiac MFH.