Epithelioid schwannoma

Solitary fibrous tumor of the thyroid gland: report of two cases and review of the literature

Presented herein are the first two Japanese cases of solitary fibrous tumor (SFT) of the thyroid gland. The patients were 64- and 41-year-old men, who underwent hemithyroidectomy for thyroid tumors. Histopathologically, the tumors were well circumscribed, and were composed of spindle cells, collagen bundles and entrapped thyroid follicles. Spindle cells and collagen bundles were mostly in a patternless arrangement with an admixture of hypo- and hypercellular areas. Proliferating spindle cells were bland, slender, and occasionally wavy without any atypia and increased mitotic figures. Immunohistochemically, they were strongly positive for CD34, CD99, and bcl-2, but negative for epithelial membrane antigen, keratin, thyroglobulin, calcitonin, thyroid transcription factor-1, alpha-smooth muscle actin, desmin, S-100 protein and CD117. Based on these findings, the two patients were diagnosed as having thyroid SFT. Neither local recurrence nor metastasis has been observed in 5 years in patient 1 or in 4 years in patient 2. Thyroid SFT is extremely rare, and only 20 cases have been reported in the English-language literature including hemangiopericytoma. Although recurrence or metastasis has not been described in any reported cases, the clinical behavior of SFT is still undetermined, therefore long-term follow up seems necessary at present.

Localized malignant mesothelioma of the epithelial type occurring as a primary hepatic neoplasm: a case report with review of the literature

We report a localized malignant mesothelioma of the epithelial type, occurring as a primary hepatic neoplasm in a 64-year-old male. He was found to have a mass located in the right lobe of the liver. Surgery was carried out with resection of the mass from the right hepatic lobe, with partial resection of the diaphragm. Grossly, an ill-defined tumor was present in the hepatic parenchyma. Histologically, the tumor displayed a predominant tubular pattern of growth with a desmoplastic stroma. The tubules were lined by a single layer of cuboidal or flattened cells with pleomorphic vesicular nuclei. A hyaluronidase-digestible, mucin-like substance was demonstrated in the lumen and tumor cytoplasm. The tumor cells were immunohistochemically positive for calretinin, HBME-1, cytokeratin, i.e. AE1/AE3 and CAM 5.2, but negative for carcinoembryonic antigen, CD 34 and Leu M1. Moreover, the tumor cells showed nuclear accumulation of the p53 oncopotein and reacted frequently with Ki-67 antibody. These findings support the concept that malignant mesothelioma of the epithelial type may occur at extrapleural sites. To the best of our knowledge, this is the first reported case of localized malignant primary mesothelioma arising in the liver.

Solitary fibrous tumor of the abdominal wall: a report of two cases immunohistochemical, flow cytometric, and ultrastructural studies and literature review

Solitary fibrous tumors have been described at many extrapleural sites in recent years. However, solitary fibrous tumors arising from somatic soft tissue occur only rarely and can pose problems in the differential diagnosis from other benign or malignant soft tissue tumors. The majority of solitary fibrous tumors occurring in the somatic soft tissue have been found in the extremities and limb girdles, and the head and neck regions. There have been only eight published cases located in the abdominal wall. We herein report two female patients who developed solitary fibrous tumors of the abdominal wall that were not in association with the underlying peritoneum. Histologically, both tumors were characterized by a variety of architectural patterns, alternating hypercellular and hypocellular areas, proliferation of plump spindle cells, thick keloid-like and/or amianthoid collagen bundles, and ectatic staghorn-like vessels. Both tumors showed a diffuse strong reaction for CD34 and vimentin as well as focal positivity for bcl-2 and smooth muscle actin. A striking predominance in females was found in a literature review of solitary fibrous tumors of the abdominal wall, contrasting with other somatic soft tissue sites which show an equal gender distribution. Interestingly, expression of estrogen but not progesterone receptor was observed in both tumors. Ultrastructurally, the tumor cells displayed features of fibroblasts with dilated branching rough endoplasmic reticulum (RER) and Golgi apparatus. Both tumors assayed by flow cytometry demonstrated a diploid DNA content with an S-phase fraction of 7.9% and 11.4%, respectively. At follow up, both patients were well without evidence of recurrence or metastasis after surgical excision.