Solitary fibrous tumor (SFT) is a fibroblastic neoplasm characterized by a branching, thin-walled dilated staghorn-shaped (hemangiopericytoma-like) vasculature and a NAB2::STAT6 gene fusion. SFTs can occur in almost any anatomical location, including superficial and deep soft tissues, visceral organs, and bone. They most commonly occur in extrapleural locations, equally affect both sexes, and are typically present in adults. Although metastasis is rare, SFTs frequently show local recurrence. The diagnosis of SFTs is difficult because of their broad histological and morphological overlap with other neoplasms. An accurate diagnosis is important for guiding disease management and prognosis. Despite advances in molecular diagnostics and therapeutic strategies, the biological complexity and unpredictable clinical behavior of SFTs present significant challenges. This review provides an updated overview of SFT, with a focus on its molecular genetics, histopathological features, and diagnostic considerations.
BACKGROUND It is important to differentiate between schwannomas and neurofibromas for the cases in which the histopathologic features overlap. Depending on the tumor type, surgeons can decide on a treatment method and whether to preserve or sacrifice the nerve; the possibility of malignant transformation in the case of neurofibromas also needs to be considered. METHODS We studied 101 cases of schwannoma and 103 cases of neurofibroma. All the hematoxylin and eosin slides for these cases were reviewed, and tissue microarrays were prepared from the representative areas. Immunohistochemical analysis was performed using antibodies for S-100 protein, calretinin, CD56 and CD34. RESULTS All the tumors except 3 neurofibromas were positive for the S-100 protein. Calretinin was found in 26.7% of the schwannomas (27/101), but it was not found in any of the neurofibromas. CD56 was positive in 77.2% of the schwannomas (78/101) and in 9.8% of the neurofibromas (10/102). CD34 was positive in 42.5% of the schwannomas (43/101) and in 80.2% of the neurofibromas (81/101). Statistically, calretinin was significantly specific for schwannomas (p<0.001) and CD56 was also sensitive for these tumors (p<0.001). On the other hand, a CD34 expression seemed highly sensitive (p<0.001) for neurofibromas. CONCLUSIONS We concluded that combined immunohistochemical analysis for calretinin, CD56, and CD34 may be very useful for differentiating schwannomas from neurofibromas.
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The differential diagnosis between MM and metastatic adenocarcinoma (MA) causes diagnostic, staging, and therapeutic dilemmas. Herein, we investigated characteristic cytologic features of MM. METHODS Cytologic specimens of MM (n=10), MA (n=25), and reactive mesothelial hyperplasia (n=10) were retrieved and reviewed from archival materials in the Department of Pathology, Seoul National University Bundang Hospital from May 2003 to July 2008. RESULTS MM showed tumor cell clusters and singly scattered malignant tumor cells forming single cell populations with sparse reactive benign mesothelial cells. In contrast, MA showed distinct two cell populations of tumor cell clusters and scattered reactive mesothelial cells. Furthermore, MM frequently exhibited a characteristic long chain-like arrangement (hand-in-hand appearance) and intercellular windows, which were rarely evident in MA. Variable nuclear size, relatively consistent nuclear-cytoplasmic ratio, bior multi-nucleation, and lacy cytoplasmic borders were also frequently observed in MM. CONCLUSIONS Differential diagnosis of MM from MA in body fluids is possible based on meticulous examination of certain cytologic parameters, which could have significant implications in staging and treatment.