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Atypical fibroxanthoma is a rare mesenchymal skin tumor of intermediate malignancy that typically occurs on sun-damaged skin of elderly patients. Histologically, it is composed of pleomorphic cells with hyperchromatic nuclei and abundant cytoplasm, commonly arranged in a spindle cell pattern. Different histologic variants have been described during the past years. We present a case of atypical fibroxanthoma containing a dense inflammatory infiltrate, which in conjunction with the existence of immunoblast-like and Reed-Sternberg-like neoplastic cells could be misinterpreted as a lymphoid neoplasm. Immunohistochemical studies revealed strong positivity of tumor cells for CD10 and negativity for cytokeratins, p63, p40, S100, SOX10, ERG, actin, desmin, B and T-cell markers, BCL6, CD15, and CD30. The inflammatory infiltrate contained a mixed reactive T- and B-cell population with negative T-cell receptor and immunoglobulin heavy rearrangements. We discuss the differential diagnosis of this entity in which clinical, immunohistochemical, and molecular features are essential to avoid the diagnosis of a lymphoproliferative disease.

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Calcifying fibrous tumour (CFT) has some of the histopathological features, such as abundant plasma cells and stromal fibrosis, that are exhibited by IgG4-related diseases (IgG4-RD). The possible role of IgG4-positive plasma cells in calcifying fibrous tumour was investigated. The aim of this study was to determine any potential relationship between IgG4-RD and CFT. Thirteen cases with a total of 16 CFTs were reviewed. Lesion samples were immunostained with anti-IgG4 and anti-IgG antibodies. The number of IgG4-positive and IgG-positive plasma cells (IgG + PC) and their ratios were estimated. Plasma cells were found in all tumours. IgG4-positive plasma cells ranged from 0 to 71 per high-power field (HPF; mean 17.8/HPF), and IgG + PC ranged from 2 to 93/HPF (mean 42.6/HPF). The IgG4/IgG ratio ranged from 0% to 80% (mean 29%). There were seven tumours with the ratio of IgG4/IgG + PC that exceeded 40%. Various degrees of stromal fibrosis were present in eight tumours. All tumours have variable calcification. The histopathological features of CFT were found to be similar to those of IgG4-RD. Some CFT also showed a high number of IgG4-positive plasma cells, and the ratio of IgG4/IgG + PC exceeded 40%, most notably in patients with concomitant inflammatory or autoimmune disease. The long-term follow-up showed no evidence of IgG4-RD in any of these patients. Our findings suggest that while CFT overlaps morphologically with IgG4-RD, it probably should not be classified as an IgG4-RD.

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Myxoinflammatory fibroblastic sarcoma is a rare soft tissue tumor with most occurring in the distal extremities of adult patients. It has a high rate of local recurrence and a low rate of metastasis. Because it may appear benign on clinical examination, and because the microscopic features are generally underrecognized, it is often inadequately treated and misdiagnosed. In this review, based upon experience and that of the literature, the intent is to highlight salient clinicopathologic features, detail the broad microscopic spectrum including high-grade aggressive variants, review the molecular features, and discuss its relation to hemosiderotic fibrolipomatous tumor.

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Gastrointestinal lesions resulting from immunoglobulin G4-related disease are classified into two types: One is a gastrointestinal lesion showing marked thickening of the wall, and the other is an IgG4-related pseudotumor. We report the case of a woman with gastric calcifying fibrous tumor undergoing endoscopic resection that contained 62 IgG4+ plasma cells per high-power field and an IgG4-to-IgG ratio of 41% in lesional plasma cells, which shared clinical and histopathological features associated with gastric IgG4-related pseudotumor. So, we postulate that calcifying fibrous tumor as part of the spectrum of IgG4-related disease might be the unifying concept with IgG4-related pseudotumor. Meanwhile, the patient had coexistent autoimmune diseases, including autoimmune atrophic gastritis, Hashimoto's thyroiditis, and possible primary biliary cirrhosis. The clinical follow-up evaluation was uneventful.

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A 46-year-old man with a past history of retroperitoneal fibrosis was admitted with an enlarged, hard right testis. The paratesticular lesion showed heterogeneous hypoechogenicity on ultrasonography, low signal intensity on T1- and T2-weighted magnetic resonance imaging (MRI), and lack of diffusion restriction on diffusion-weighted MRI. Following steroid treatment, the paratesticular mass was decreased in size on follow-up computed tomography. The radiologic and clinical features are recognized as a manifestation of immunoglobulin G4-related sclerosing disease involving the paratesticular region and retroperitoneum.

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Paratesticular fibrous pseudotumor (nodular periorchitis, inflammatory pseudotumor of the spermatic cord) is a rare, benign condition of unknown etiology characterized by solitary or multiple intrascrotal nodules composed of dense fibrous tissue with a variable, sometimes sparse inflammatory infiltrate. Based on certain similarities to other fibroinflammatory disorders characterized by infiltrates of IgG4-expressing plasma cells and recently subsumed under the heading of IgG4-mediated diseases, we investigated the plasma cell distribution and immunoglobulin isotypes in three cases of paratesticular fibrous and inflammatory pseudotumor. All three cases showed a high number of IgG4-positive plasma cells with an IgG4 to IgG ratio of 44-48%. This finding indicates that paratesticular fibrous pseudotumor might belong to the growing list of IgG4-related diseases, which by now includes such diverse entities as retroperitoneal fibrosis, sclerosing pancreatitis and cholangitis, Riedel's thyroiditis, or sclerosing sialadenitis.

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Sclerosing angiomatoid nodular transformation (SANT) is a peculiar splenic vascular lesion that is characterized by marked stromal sclerosis and the presence of plasma cells, which shares histopathological features associated with IgG4-related sclerosing disease. The cinicopathological features of 10 cases of SANT were reviewed and immunohistochemistry with IgG4 and IgG antibodies was performed. Nine other various splenic lesions served as controls. Five cases of SANT were found incidentally. Three cases of SANT had multiple tumors and five had associated abdominal disseminated calcifying fibrous tumors (CFT). IgG4+ plasma cells were found in all of the cases of SANT and in calcifying fibrous tumors. The densities of IgG4+ and IgG+ cells and the IgG4/IgG ratios were significantly higher in SANT than in control spleens (P= 0.001, 0.006, and 0.028, respectively). Serum IgG4 concentration was elevated in one case. In conclusion, SANT can occur either as a solitary or as multiple tumors. Frequent association with abdominal disseminated CFT simulating carcinomatosis was observed. A statistically significant number of IgG4+ plasma cells was found in all of the cases of SANT and the associated CFT. Whether they are related to the IgG4-related sclerosing disease or not is debatable and warrants further investigation.

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Solitary fibrous tumors are benign neoplasms of mesenchymal origin. They usually arise from the visceral or parietal pleura and peritoneum, although they have been found in many areas throughout the body. We report a case of solitary fibrous tumor of the parapharyngeal space. Microscopically, the tumor contained spindle cells with areas of marked hypercellularity without a definitepattern. Consistent with a benign lesion, there were few mitoses and no necrosis. The tumor cells stained strongly positive for CD34 and vimentin. At the 2-year follow-up, the patient was well and free of local and/or distant disease.

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Solitary fibrous tumor of the pleura (SFTP) is a rare, benign, slow-growing neoplasm that arises from the submesothelial cells of the pleura. Usually, resection of the tumor and adjacent structures are sufficient for resolution. Nowadays, videothoracoscopy (VTC) allows adequate access for the surgical treatment of these tumors. CD34 antigen positivity is a differential feature with mesothelioma. We present our experience with 15 patients with SFTP (nine women and six men) who underwent surgical resection in the last 12 years (10 thoracotomies, one sternotomy and four VTC). Only four patients were symptomatic at diagnosis. In our opinion, VTC is a less invasive diagnostic and therapeutic approach than thoracotomy that provides an adequate approach for the resection of SFTP in selected patients. Because of the malignant potential of this tumor, long-term follow-up is mandatory.

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Solitary fibrous tumor (SFT) arises in the pleura and less commonly in extrapleural sites. SFT can be found in various head and neck sites. SFTs of the nasal cavity and paranasal sinuses are extremely rare with only ten previously reported cases in the world literature. This case report presents an additional case of SFT of the nasal cavity underlining the benign pattern and the bleeding tendency of nasal SFT, that surgeons managing these tumors should be aware of. Diagnostic procedure, clinical and histopathological findings as well as immunoreactivity of this tumor are discussed, with a review of the current literature.

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Previous studies have shown that immunohistochemical stains for histiocytes are immunoreactive for melanomas. Accordingly, their value in differentiating histiocytes and histiocytic lesions from melanomas was questioned. PG-M1, the most specific histiocytic marker, was not evaluated in these studies. Our aims were to assess the reactivity of PG-M1 with a series of primary cutaneous and metastatic melanomas and to establish the potential usefulness of this antibody in the differentiation between histiocytes and histiocytic tumors and melanomas. PG-M1 staining was performed in 50 primary cutaneous and metastatic melanomas. For comparison, additional sections were stained with KP-1 and lysozyme (commonly used as histiocytic markers) and with S-100 and HMB-45 (commonly used as melanoma markers). The intensity (1+, 2+) and extent (1+ to 4+) were recorded semiquantitatively. PG-M1 stained weakly (1+) and focally (2+) only four cases of melanoma (8%). In contrast, histiocytes were strongly reactive for PG-M1 in all cases, being readily differentiated from melanoma cells including the positive cases. KP-1 stained melanoma cells in 44 cases (88%), lysozyme in 11 cases (22%), S-100 in 50 cases (100%), and HMB-45 in 48 cases (96%). No changes were found after restaining of selected KP-1 and lysozyme positive melanomas using an endogenous avidin/biotin blocking kit. PG-M1 is helpful in discriminating histiocytes and histiocytic lesions from melanoma cells. We recommend its inclusion in any antibody panel put together to distinguish between them.

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Solitary fibrous tumours (SFT), originally described in the pleura, were subsequently recognized in numerous extrapleural sites. This suggests that a common stem cell, present in various organs and tissues, may be at the origin of SFT and that specific factors may be involved in the proliferation of such cells. Recently it has been described that steroid hormone receptors, progesterone receptors in particular, are expressed by extrapleural SFT. In addition, progesterone may participate as growth factor in many CD34(+) stromal neoplasms, which express low levels of the hormone receptors. The present study analysed the expression of androgen (AR), oestrogen (ER) and progesterone (PR) receptors in a series of 32 pleural SFT, 10 mesotheliomas and in reactive tissue of chronic pleuritis. ER and AR were never expressed by SFT or by chronic pleuritis, whereas PR were demonstrated in 2/16 "large" (>8 cm) and in 6/16 "small" (< or =8 cm) pleural SFT (all expressing CD34, bcl-2 and CD99). PR(+) SFT had a significantly higher proliferative activity (p = 0.04) (Ki-67 mean value 6.5%) and lower p27(kip1) (mean value 51.5%) expression than the PR(-) cases (Ki-67 mean value 3.81% and p27(kip1) mean value 57.86%). One of the cases expressing a high level of PR (80%) recurred 1 year after first surgery and the recurrence was PR(+) as well, but with a lower percentage of nuclear receptor expression (12%). In addition, in chronically inflamed subserosal tissue, a subpopulation of CD34(+) endothelial and interstitial dendritic cells was identified, which also expressed PR. These findings suggest that the CD34(+) submesothelial interstitial dendritic cells, activated during reactive processes, may be the stem cells that give rise to SFT, and that progesterone might participate in the growth of SFT through modulation of its specific receptors.

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Effects of Schistosoma mansoni infection on anti-tumor immunity were examined in CBF1 mice with ultraviolet-induced UVfemale1 fibrosarcoma cells. Although many laboratory established tumor cells had rejection mechanisms independent of CD4(+) T cells, we confirmed that CD4(+) cells had significant roles in rejection of UVfemale1 cells in the syngeneic CBF1 mice. When we prepared two CBF1 mouse groups, S. mansoni-infected and schistosome-free, the former group showed up-regulation of Th2-like response to UVfemale1 cells, whereas the latter group mice showed rather type 1-dominant patterns. Cytotoxic activity against UVfemale1 cells tested in vitro, which was attributed to CD8(+) cells, was significantly weaker in S. mansoni-infected mice compared with infection-free mice. In tumor challenge experiments in vivo, we observed that rapid and complete rejection of UVfemale1 cells required the presence of CD8(+) T cells. Under only CD4-depleted situation, survival of tumor cells in schistosome-free mice was prolonged up to 1 month or more. Under the presence of both CD4(+) and CD8(+) cells, S. mansoni infected mice rejected the challenged UVfemale1 cells as was seen in normal mice. However, when CD8(+) cells were depleted from S. mansoni-infected mice, inoculated UVfemale1 cells grew more rapidly than in infection-free mice. Our results suggest that functionally polarized cytokine patterns in schistosome-infected hosts promote rapid tumor growth.

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Solitary fibrous tumor (SFT) is an uncommon mesenchymal tumor that typically arises in the pleural cavity. Comprised of spindled cells characteristically arranged in diverse architectural patterns, SFT histologically simulates a variety of benign and malignant mesenchymal tumors. The diagnosis of SFT has been refined by the availability of newer immunohistochemical markers such as CD-34 and factor XIIIa, facilitating the identification of SFTs arising in multiple extrapleural sites, including the skin. We describe three cases of primary cutaneous SFT, review the literature, and discuss the histologic and immunohistochemical differential of other cutaneous tumors that SFT can mimic.

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The clinical, radiologic and pathologic features of a case of parasagittal solitary fibrous tumor of the meninges are reported. The patient was a 44 year-old male who presented with a complex partial seizure and a history of headaches and confusion. Radiological studies showed a large extra-axial dural-based mass in the right parietal region, predominantly isointense with gray matter and hypointense with respect to white matter on T1-weighted images, and hypointense with respect to gray matter on T2-weighted images. At surgery, the mass was very vascular, quite firm and very adherent to the convexity. Histologically the tumor was composed of spindle-shaped cells growing in fascicles within a collagenous matrix. Solitary fibrous tumor of the meninges is a newly described entity, which should be kept in mind in the clinical and radiological differential diagnosis of extra-axial brain tumors.

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Solitary fibrous tumors are rare neoplasms that most commonly involve the pleura, mediastinum, and lung. Because they lack distinctive histologic features, immunologic staining has frequently been employed to exclude other neoplasms in the differential diagnosis. Their reported phenotype to date is generally negative, notably for muscle-type actins, desmin, keratin, and S-100 protein. Although this testing is of some help, it does not serve to distinguish all processes in the differential diagnosis, and when it does, it places too great an emphasis on a negative finding to make a diagnosis. We report here that CD34 monoclonal antibodies reacted with 11 of 14 solitary fibrous tumors in paraffin sections. Thus, they provide a positive marker that distinguishes the solitary fibrous tumor from most elements in the differential diagnosis.

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