Fibrous Histiocytoma: An analysis of the storiform pattern

Summary A storiform pattern is an important structural feature of fibrous histiocytoma (FH). In this analysis reconstructions of histological patterns were carried out from drawings. Highly cellular FH with only a suggestion of storiform pattern and small star-formations were seen, there were other lesions with more pronounced fiber formation which showed more distinct and larger storiform stars. These structures can frequently be followed for only 3 sections of 5 micron thickness. In contrast to leiomyomas or meningioma, no regular or consistent orientation of these structures with respect to vessels is evident.Storiform structures apparently develop at the periphery of adjacent proliferating cells groups. They show a typical and diagnostically significant histological pattern, which was found to some degree in all FH examined.This study is dedicated to Prof. Dr. E. Uehlinger, who celebrates his 80th birthdayThis study was supported by the Wilhelm-Sander-FoundationThe histological laboratory work was carried out by Mrs. B. Weidenhammer     

Incidence and histological structure of the storiform pattern in benign and malignant fibrous histiocytomas

Summary A starlike arrangement of cells and fibers, the storiform pattern, was found to be a typical, but not obligatory, histological feature of benign and malignant fibrous histiocytomas. In 155 benign fibrous histiocytomas storiform structures were missing in 29 cases, chiefly of the fibroblastic type comparable with classical dermatofibroma. 12 of 70 malignant fibrous histiocytomas did not reveal storiform structures, especially the cellular pleomorphic variant, i.e. the classical pleomorphic sarcoma.Storiform structures were either small and highly cellular with few fibers (collagen type III), or larger, less cellular, but with abundant fibers (collagen type I). There was no sharp demarcation between these two extremes, but many transitional structures or patterns were seen. The histiocytic nature of the cells was demonstrated in both variants of storiform structures by immunhistochemical methods on paraffin embedded material. Alpha₁-anti-chymotrypsin was especially valuable in this respect.The study was supported by the Wilhelm-Sander-FoundationDedicated to Prof. Dr. W. Büngeler to his 80^th birthday     

Extrathoracic solitary fibrous tumors: their histological variability and potentially aggressive behavior

The histological variability of solitary fibrous tumors may contribute to the difficulty in diagnosing these neoplasms, especially when they arise in extrathoracic sites. Like intrathoracic lesions, the behavior of extrathoracic solitary fibrous tumors is currently unpredictable because these types of tumor have only recently been recognized. This study therefore was undertaken to examine the clinical behavior and histological, immunohistochemical, and ultrastructural features of 24 extrathoracic solitary fibrous tumors with long-term follow-up. The patients comprised 10 men and 14 women, between 30 and 85 years of age (mean, 51 years). Ten tumors were located in the retroperitoneum or pelvis, 5 in the trunk, 4 in the extremities, 2 in the orbital region, and 1 each in the kidney, uterine cervix, and meninges. All of the tumors showed a classic morphological appearance, diffuse and strong immunoreactivity for both vimentin and CD34, and variable reactivity for bcl-2. All 7 cases examined ultrastructurally contained fibroblasts and myofibroblasts. Six tumors contained multinucleated giant cells, and in 4 cases these lined pseudovascular spaces with mononuclear cells, thus resembling giant cell angiofibroma and giant cell fibroblastoma. Other potentially similar spindle cell neoplasms mixed with adipose tissue, such as dendritic fibromyxolipoma, lipomatous hemangiopericytoma, cellular angiofibroma, and spindle cell lipoma, were considered in the differential diagnosis. One tumor displayed atypical histological features in the form of increased cellularity and nuclear pleomorphism, but this patient has remained free of disease for 14 years. Another 2 patients developed local recurrences at 6 months and 5 years, and a further patient developed pulmonary metastases that were diagnosed after 7 years. These tumors lacked any atypical histological features in the primary lesions. No patient has so far died of the disease. In conclusion, most extrathoracic solitary fibrous tumors appear to pursue a benign course, although, because some have the potential to recur or metastasize, careful long-term follow-up is necessary for all patients.     

Malignant fibrous histiocytoma of bone. Clinical pathology and histological diagnosis

Malignant fibrous histiocytoma of bone is a histologically well-defined tumor. Our aim is to describe five own cases and to analyze the published cases in order to demonstrate, the controversial aspects of clinical pathology. The essential histological criteria are the storiform tissue pattern and the presence of fibroblastic and histiocytic cells and giant cells. Inclusive of our cases, the total number reported stands at 196. There are features of malignant fibrous histiocytoma of bone about which there is almost general agreement: 1. The tumor occurs at all ages with an average onset from the age of 10 to the age of 50. 2. The tumor occurs in both the long and flat bones, but the main sites are the distal femur and the proximal tibia. 3. The tumor lacks any initial distinctive features in its clinical phase, but with respect to its biological behaviour, malignant fibrous histiocytoma of bone can be distinguished from osteosarcoma.     

Cytomorphologic features of classic and variant lobular carcinoma: A comparative study

There are several subtypes of lobular carcinoma (LC), and their cytomorphologic features differ from classic lobular carcinoma (CLC). The finer details of the differences between CLC and variant lobular carcinoma (VLC) have not been adequately studied. A comparative study of 54 cases of CLC and VLC was done in order to verify any statistically significant differences between them. All cases had histologic confirmation of the diagnosis. Six parameters, which included cellularity, signet-ring cells, intracytoplasmic lumina (ICL), anisonucleosis, cell size, and prominent nucleoli, were studied. The only statistically significant findings were cellularity and cell size when compared to CLC. The cellularity in VLC was higher and the cells in VLC were larger when compared to CLC. There are no definite diagnostic features to identify VLC; however, in a cellular specimen with plenty of large cells with other features of LC, one should have a high index of suspicion of VLC.     

77例胃肠道间质肿瘤的病理形态学及免疫组化研究

目的：研究胃肠道间质瘤（GIST）的病理形态及免疫组化特点,方法：应用光镜观察77例GIST的形态特征,用免疫组化S－P法检测c-kit(CD117),CD34,vimentin,SMA及S－100蛋白在GIST中的表达情况。结果：GIST的瘤细胞较经典的平滑肌瘤更丰富,胞质嗜酸较弱,瘤细胞为酸形或上皮样,或酸形与上皮样细胞混合存在,胞质内常见空泡形成;排列成交织刺状、弥散片状、栅栏状或轮辐状、较为特征的是细胞团巢形成。常见间质或见管壁玻变。原发于肠系膜者恶性潜力较高。CD117和CD34的阳性率分别为90％和92％,结论：胃肠道间质肿瘤有较为特独的组织学形态,CD117和CD34联合使用可协助鉴别诊断。     

Testicular feminisation syndrome: unusual gonadal histology in an elderly patient.

The gonads of an elderly patient with a typical testicular feminisation syndrome are described. The unusual histological features consisted of total absence of testicular tubular structures or remnants thereof and distinct proliferation of smooth muscle bundles. In addition, there was fibrous proliferation, areas of ovarian stroma, and rare Reinke crystalloids within Leydig cells. The complete tubular absence may have been the result of fibrous replacement related to patient's advanced age, while the muscular proliferation may have been of hamartomatous nature. Thus, it seems that in elderly patients with testicular feminisation syndrome, the histological appearance of the gonads may vary considerably from that in younger individuals, and in such cases the correct diagnosis should be based mainly on clinical and cytogenetic findings.     

A comparative study of fibrous dysplasia and osteofibrous dysplasia with regard to expressions of c-fos and c-jun products and bone matrix proteins: a clinicopathologic review and immunohistochemical study of c-fos, c-jun, type I collagen, osteonectin, osteopontin, and osteocalcin

Fibrous dysplasia and osteofibrous dysplasia are both benign fibro-osseous lesions of the bone and are generally seen during childhood or adolescence. Histologically, the features of these bone lesions sometimes look quite similar, but their precise nature remains controversial. We retrospectively studied clinicopathologic findings in 62 cases of fibrous dysplasia and 20 cases of osteofibrous dysplasia with regard to their anatomic location and histological appearance. From among these cases, the immunohistochemical expressions of c-fos and c-jun proto-oncogene products and bone matrix proteins of type I collagen, osteonectin, osteopontin, and osteocalcin were evaluated in 20 typical fibrous dysplasias and 17 osteofibrous dysplasias using paraffin sections, and these expressions were then assessed semiquantitatively. Microscopically, fibrous dysplasia showed various secondary changes, such as hyalinization, hemorrhage, xanthomatous reaction, and cystic change in 22 of the 62 cases (35%). This was a higher incidence than in osteofibrous dysplasia, in which only 2 of the 20 cases (10%) showed such changes. In the elderly fibrous dysplasia cases, the cellularity of fibroblast-like cells was rather low, and those cases were hyalinized. Almost all of the cases of fibrous dysplasia and osteofibrous dysplasia showed positive expressions of c-fos and c-jun products. The expressions of type I collagen and osteopontin showed no difference between fibrous dysplasia and osteofibrous dysplasia. Immunoreactivity for osteonectin in bone matrix was detected in only 1 case of fibrous dysplasia (1 of 20), whereas it was recognized in 14 of the 17 cases of osteofibrous dysplasia. Furthermore, the immunoreactivity for osteocalcin in bone matrix and fibroblast-like cells was higher in fibrous dysplasia than it was in osteofibrous dysplasia, semiquantitatively. Our immunohistochemical results regarding osteonectin and osteocalcin suggest that the bone matrix of fibrous dysplasia is somewhat more mature than that of osteofibrous dysplasia, and that the fibroblast-like cells in fibrous dysplasia share some phenotypic features with osteoprogenitor cells of normal osteogenic tissues. Fibrous dysplasia and osteofibrous dysplasia share some similar histological features, including c-fos and c-jun expressions, although different clinicohistologic features and immunohistochemical expressions of osteonectin and osteocalcin were observed. These features suggest that the mechanisms behind the development of fibrous dysplasia and osteofibrous dysplasia are similar, but this is not necessarily indicative of a closer relationship between the 2 diseases.     

Growth patterns of juvenile nasopharyngeal fibromas. A histological analysis on the basis of 40 cases

Juvenile nasopharyngeal angiofibroma is a unique process characterized by an exclusive localization in the nasopharynx of young male patients, and a typical histological pattern composed of angiomatous and fibrous structures. Forty tumors of patients 7 to 25 years of age were investigated. The tumors showed a characteristic zonal organization. Apart from the superficial epithelium the lesions can be subdivided into a subepithelial myxoid-fibrous zone followed by a proliferative capillary fibroblastic cambium layer. In the latter, either the capillary component or the fibroblasts can prevail. The main part is composed of sinus-like vascular channels and a fibrous component. The gaping vascular channels differing in caliber are lined by a single layer of epithelium and surrounded by single or mostly an incomplete rim of smooth muscle cells. Elastic fibres are always lacking. The fibrous component exhibits a changing cellularity and fibre content. Myxoid foci can be encountered, often associated with a pleomorphic cell pattern. Generally, however, fibre structures and foci or large areas of hyalinization predominant in direction to the central parts. In older lesions the fibrous tissue is prevailing. The capillary fibroblastic cambium zone disappears and areas of hyalinization are enlarged. In five cases relapses showing the same structural features were observed. Juvenile nasopharyngeal angiofibromas are discussed as a specific but non-autonomous proliferating growth process which is characterized by 1. specific age and sex incidence, probably in relation to hormones, 2. typical histological pattern and cytological criteria, including local infiltration of the surrounding musculature and bones, 3. origin in the same region corresponding to the membrana buccopharyngea and constant blood supply by the arteria maxillaris interna, or its end artery, the arteria sphenopalatina. According to the corpus cavernosum-like structures, comparable to erectile tissue, the nasogenital relations are discussed. Juvenile nasopharyngeal angiofibromas are defined as a specific clinicopathological entity.     

The histological spectrum of subperiosteal fibrocartilaginous pseudotumor of long bone (focal fibrocartilaginous dysplasia)

Clinicopathological features in six cases of focal fibrocartilaginous dysplasia (FFCD) which involved either the tibia (n = 4) or the femur (n = 2) were reviewed. All cases presented clinical and radiological characteristic features, and histopathological findings were analyzed in five of the six cases. The subject group comprised three boys and three girls, ages ranged from 12 to 18 months. Histologically, the individual lesions showed regional variation in cellularity, amount of fibrous and cartilaginous components. Paucicellular areas were mainly composed of dense fibrous tissue while more cellular areas contained foci of fibrocartilaginous element. The chondrocytes and stellate cells around cartilaginous area were positive for S-100 protein. One case contained both hyaline and fibrocartilage, and architecturally mimicked normal tendinous insertion. One case, which involved proximal tibia, was purely composed of fibrous tissue without fibrocartilage. All cases formed undulating and irregular borders against underlying cortical bone. Histopathologically variable spectrum suggests a strong possibility of undergoing transition from initial cellular and cartilagnous to late paucicellular, fibrous phase. Although any evidence that can explain basic pathogenesis or prognostic histological parameter is lacking, we believe that the term FFCD is not relevant because the presence of fibrocartilage is not an essential feature, and it can cause confusion with other pathological processes. We propose the term 'subperiosteal fibrocartilaginous pseudotumor of long bone' for this unique clinicopathological entity with which heterologous cartilaginous element can be associated.     

Malignant fibrous histiocytoma of the right ventricle of the heart

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 pleo-morphism, storiform pattern and abundant mitoses. Immu-nohistochemical and electron microscopical findings were compatible with MFH, and excluded the possibility of leio-myosarcoma 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.     

A comparative study of fibrous dysplasia and osteofibrous dysplasia with regard to expressions of c-fos and c-jun products and bone matrix proteins: A clinicopathologic review and immunohistochemical study of c-fos, c-jun, type I collagen, osteonectin, osteopontin, and osteocalcin

Fibrous dysplasia and osteofibrous dysplasia are both benign fibro-osseous lesions of the bone and are generally seen during childhood or adolescence. Histologically, the features of these bone lesions sometimes look quite similar, but their precise nature remains controversial. We retrospectively studied clinicopathologic findings in 62 cases of fibrous dysplasia and 20 cases of osteofibrous dysplasia with regard to their anatomic location and histological appearance. From among these cases, the immunohistochemical expressions of c-fos and c-jun proto-oncogene products and bone matrix proteins of type I collagen, osteonectin, osteopontin, and osteocalcin were evaluated in 20 typical fibrous dysplasias and 17 osteofibrous dysplasias using paraffin sections, and these expressions were then assessed semiqnantitatively. Microscopically, fibrous dysplasia showed various secondary changes, such as hyalinization, hemorrhage, xanthomatous reaction, and cystic change in 22 of the 62 cases (35%). This was a higher incidence than in osteofibrous dysplasia, in which only 2 of the 20 cases (10%) showed such changes. In the elderly fibrous dysplasia cases, the cellularity of fibroblast-like cells was rather low, and those cases were hyalinized. Almost all of the cases of fibrous dysplasia and osteofibrous dysplasia showed positive expressions of c-fos and c-jun products. The expressions of type I collagen and osteopontin showed no difference between fibrous dysplasia and osteofibrous dysplasia. Immunoreactivity for osteonectin in bone matrix was detected in only 1 case of fibrous dysplasia (1 of 20), whereas it was recognized in 14 of the 17 cases of osteofibrous dysplasia. Furthermore, the immunoreactivity for osteocalcin in bone matrix and fibroblast-like cells was higher in fibrous dysplasia than it was in osteofibrous dysplasia, semiquantitatively. Our immunohistochemical results regarding osteonectin and osteocalcin suggest that the bone matrix of fibrous dysplasia is somewhat more mature than that of osteofibrous dysplasia, and that the fibroblast-like cells in fibrous dysplasia share some phenotypic features with osteoprogenitor ceils of normal osteogenic tissues. Fibrous dysplasia and osteofibrous dysplasia share Some similar histological features, including c-fos and c-jun expressions, although different clinicohistologic features and immunohistochemical expressions of osteonectin and osteocalcin were observed. These features suggest that the mechanisms behind the development of fibrous dysplasia and osteofibrous dysplasia are similar, but this is not necessarily indicative of a closer relationship between the 2 diseases.     

Immunohistochemical and ultrastructural studies of a primary aortic intimal sarcoma

An intimal sarcoma of the abdominal aorta in a 63-year-old woman is reported. The clinical symptoms consisted of chronic arterial hypertension, vomiting and epigastric pain. Treatment was operative, but the patient died 20 hours after surgery. The studies were performed on a surgical specimen and on autopsy material. The aortic tumour consisted of pleomorphic spindle-shaped and giant cells. In the vertebral metastases a storiform pattern of the tumour cells was found. No specific features characteristic for leiomyogenic, lipogenic or an endothelial nature of the tumour giant cells was disclosed in electron microscopy and the picture rather indicated their histiocytic character. Of the 18 cellular markers studied, the immunostainings for vimentin and alpha-1-antichymotrypsin were evidently positive. The tumour was classified as a pleomorphic intimal aortic sarcoma probably a malignant fibrous histiocytoma (MFH). The literature on 26 previously published aortal tumours is reviewed with emphasis on their topographical distribution and histological classification. In only 4 previous cases was the final diagnosis supported by electron microscopical or immunopathological findings. The role of marker studies in the classification of aortal tumours is discussed.     

Cytologic diagnosis of invasive lobular carcinoma: factors associated with negative and equivocal diagnoses

Fine-needle aspiration biopsy (FNAB) of invasive lobular carcinoma (ILC) is associated with notoriously high rates of false negative and equivocal diagnoses. To identify causative factors, we reviewed the cytologic features of presurgical FNAB smears of ILC and correlated the cytologic findings with the number of passes, tumor size, mammographic findings, and the histologic characteristics of the tumor. Smear cellularity, presence of single intact epithelial cells, nuclear size, nuclear atypia, palpability of the tumor, and histologic type of ILC (classic versus nonclassic) were statistically significant in establishing an unequivocally positive diagnosis. We also found that the cytologic cellularity of the lesion does not reflect the actual cellularity of the tumor but instead is an indicator of the architectural arrangement of the neoplastic cells; tumors that form epithelial cell groups, such as in nonclassic ILC, tend to yield more cellular aspirates that are diagnostic for carcinoma. In contrast, classic ILC, in which single neoplastic cells are embedded in fibrous stroma, is more likely to yield a paucicellular smear with subtle atypia and rare single intact epithelial cells. As such, an inconclusive diagnosis in a certain percentage of classic ILC cases may be unavoidable.     

Fibronectin in relation to growth patterns of fibrohistiocytic tumours--an immunohistochemical study of benign and malignant fibrous histiocytomas

Benign and malignant fibrous histiocytomas are composed of an admixture of fibroblast-like and histiocyte-like cells and of a changing amount of fibre structures which tend to be arranged in a so-called storiform pattern. In order to study the organization of the extracellular matrix, the distribution of fibronectin was investigated immunohistochemically. Using the PAP technique and the indirect immunofluorescence method, paraffin sections of formaldehyde fixed tissue specimens of 25 tumours (12 benign fibrous histiocytomas, 12 malignant fibrous histiocytomas, and 1 atypical fibroxanthoma) were studied. A pretreatment with hyaluronidase and proteolytic enzymes (trypsin, pronase, pepsin) was performed to unmask the antigen. Best results were obtained with pronase E or, sometimes even better, by employing a combination of pronase E and hyaluronidase. Generally fibronectin could be demonstrated in the matrix substances of fibrohistiocytic tumours, but the immunohistochemical staining patterns of benign and malignant tumours differed. In benign fibrous histiocytomas, a regular distribution of fibronectin was found in cellular areas. Parallel to formation of collagen fibres, the reaction decreased and in dermatofibromas showing abundant hyalinized collagen the staining proved to be quite weak. In malignant fibrous histiocytomas, the immunostaining was very irregular. In cellular areas consisting of spindle cells, an intense reaction could be observed. Tumours with storiform or fascicular fields exhibit a delicate network of fibronectin encircling individual fibroblast-like cells. In the course of fibre formation, the matrix staining for fibronectin revealed a distribution similar but not identical with that obtained with the reticulin stain. Simultaneous to the occurrence of collagen fibre bundles, fibronectin decreased and in areas of hyalinization the staining was considerably diminished. In areas of undifferentiated small cells, in myxoid zones as well as foci of xanthoma cells, and in pleomorphic portions the immunostain was negative. The distribution in atypical fibroxanthoma is similar to that observed in storiform and pleomorphic variants of malignant fibrous histiocytomas. The results support the suggestion that fibronectin is the first sign of the typical basic pattern of fibrohistiocytic tumours preceding the formation of reticulin and collagen fibres. The expression of fibronectin on cell surfaces as well as in intercellular matrix may be closely related to the organization of the growth patterns of fibrohistiocytic tumours.     

The spectrum of histologic growth patterns in benign and malignant fibrous tumors of the pleura.

A review of the histologic growth patterns in 50 cases of benign and malignant fibrous tumors of the pleura (localized or solitary fibrous tumor, fibrous mesothelioma) is presented. Two major histologic growth patterns were observed admixed in various proportions: solid spindle and diffuse sclerosing. The solid spindle growth pattern assumed various configurations, including fascicular areas, storiform and herringbone formations, angiofibroma and hemangiopericytoma-like areas, synovial sarcoma-like areas, and neural-type palisading, thus simulating a variety of soft-tissue neoplasms. The diffuse sclerosing pattern, although rarely assuming a dominant role, was present in varying proportions in virtually all cases. In areas with extensive sclerosis, focal degeneration of collagen simulating tumor necrosis was often present. Other less frequently observed features were the formation of "amianthoid" fibers, multinucleated giant cells, and foci of metaplastic ossification. On ultrastructural and immunohistochemical examination, the tumor cells showed nondistinct features. Due to the extreme variability in morphologic appearances and the lack of distinctive ultrastructural or immunohistochemical characteristics, these tumors can pose a significant diagnostic problem. Familiarity with their histologic appearances and correlation with the gross findings and clinical setting are essential for arriving at the correct diagnosis.     

Ossifying subcutaneous tumor with myofibroblastic differentiation

Immunohistochemical, ultrastructural, and flow cytometric studies were performed on an ossifying soft-tissue tumor, presumed to be a variant of ossifying fibromyxoid tumor of soft parts, which was located in the subcutis of the left buttock of a 76 year old Japanese woman. Histologically, this was a benign-looking spindle, oval, or round cell lesion, having a fibrous capsule with a discontinuous rim of bone as seen in typical cases. However, this lesion was also characterized by a high degree of cellular proliferation in storiform and whorl arrangements, extensive ossification, osteoid and metaplastic bone formation and absence of myxoid features. In an immunohistochemical study using formalin-fixed, paraffinembedded sections, many tumor cells expressed vimentin, S-100 protein, Leu-7, neuron specific enolase, and desmin. Ultrastructuraliy, this neoplasm consisted of fibroblast-like cells and myofibroblast-like cells. This tumor had an aneuploid DNA content. No recurrence has been observed for 16 months. These results suggest that the neoplastic cells may show the phenotypic expressions of myofibroblast and also osteogenic differentiation.     

Solitary fibrous tumors ('fibrous mesotheliomas') of the peritoneum. A report of three cases and a review of the literature

The clinical and pathologic features of three new and seven previously described solitary fibrous tumors of the peritoneum are reviewed. The male-female ratio has been 7:3, and the patients have ranged from 27 to 64 (average, 54) years of age. Most of the tumors have been large (over 9 cm) and have been responsible for significant symptomatology. Microscopic examination has typically shown mildly to moderately cellular fibrous tumors with prominent hyalinization, although occasional tumors have exhibited focal marked cellularity. Cytologic atypicality and mitotic figures have been rare or absent. Immunohistochemical stains have shown positivity only for vimentin. There has been no evidence of recurrence in any of the cases. The clinical, gross, histologic, and immunohistochemical features of these tumors are identical to those of fibrous tumors of the pleura, and a similar origin from submesothelial mesenchyme is likely.     

Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model

Solitary fibrous tumor represents a spectrum of mesenchymal tumors, encompassing tumors previously termed hemangiopericytoma, which are classified as having intermediate biological potential (rarely metastasizing) in the 2002 World Health Organization classification scheme. Few series have reported on clinicopathological predictors with outcome data and formal statistical analysis in a large series of primary tumors as a single unified entity. Institutional pathology records were reviewed to identify primary solitary fibrous tumor cases, and histological sections and clinical records reviewed for canonical prognostic indicators, including patient age, tumor size, mitotic index, tumor cellularity, nuclear pleomorphism, and tumor necrosis. Patients (n=103) with resected primary solitary fibrous tumor were identified (excluding meningeal tumors). The most common sites of occurrence were abdomen and pleura; these tumors were larger than those occurring in the extremities, head and neck or trunk, but did not demonstrate significant outcome differences. Overall 5- and 10-year metastasis-free rates were 74 and 55%, respectively, while 5- and 10-year disease-specific survival rates were 89 and 73%. Patient age, tumor size, and mitotic index predicted both time to metastasis and disease-specific mortality, while necrosis predicted metastasis only. A risk stratification model based on age, size, and mitotic index clearly delineated patients at high risk for poor outcomes. While small tumors with low mitotic rates are highly unlikely to metastasize, large tumors ≥15?cm, which occur in patients ≥55 years, with mitotic figures ≥4/10 high-power fields require close follow-up and have a high risk of both metastasis and death.     

Pediatric pigmented dermatofibrosarcoma protuberans (Bednár tumor): case report and review of the literature with emphasis on the differential diagnosis

Dermatofibrosarcoma protuberans (DFSP) is a fibrous tumor of intermediate malignant potential that usually affects the trunk of young to middle-aged adults. On histological examination, it is characterized by a monomorphous population of spindle cells arranged in a storiform or cartwheel pattern. Bednár tumor (BT), formerly known as storiform pigmented neurofibroma, is currently considered the pigmented variant of DFSP due to the histological and cytogenetic similarities between these two lesions. There are very few reports on BT affecting pediatric patients. We describe a case of BT affecting the dorsal aspect of the left forearm of a 6-year-old-male patient and emphasize the diagnostic clues to distinguish this unusual cutaneous neoplasm from other pigmented lesions, including pigmented (melanotic) neurofibroma (PMN), psammomatous melanotic schwannoma (PMS), neurocristic cutaneous hamartoma (NCH), and desmoplastic malignant melanoma (DMM). We would like to stress that surgical pathologists and dermatopathologists need to be aware of the prototypical histological appearance of BT as there is the risk of misdiagnosing it either as pigmented tumors associated with neurocutaneous syndromes, such as PMN and PMS, or as a highly malignant melanocytic neoplasm (DMM).