Cellular Dermatofibroma Research Articles

High-grade sarcoma arising within a cellular dermatofibroma

High-grade sarcoma arising within a cellular dermatofibroma

150例皮肤纤维瘤组织病理与临床分析

Objective To analyze histopathological and clinical features of dermatofibroma, and to explore the relationship between them. Methods Clinical and histopathological data were collected from 150 patients with histopathologically confirmed dermatofibroma in Department of Pathology, Shanghai Skin Disease Hospital from September 2017 to August 2018, and analyzed retrospectively. Results Among the 150 patients, 65 were males, and 85 were females. Their age was 42 ± 13.8 years, and the course of disease ranged from 3 months to 30 years. Some of the patients had concomitant symptoms, mainly manifesting as itching, some had spontaneous pain and mild tenderness, and 18 patients had a history of injury, insect bite or infection at lesion sites. Skin lesions mainly occurred on the extremities (107 cases, 71.3%) , and most were solitary (105 cases, 70%) . Before pathological examinations, 102 cases were clinically diagnosed as dermatofibroma, 16 as epidermoid cyst, 13 as pigmented nevus, 3 as keloid, 12 as skin mass, 1 as malignant melanoma, 1 as xanthogranuloma, 1 as prurigo nodularis, and 1 as neurofibroma. Among 169 hematoxylin and eosin (HE) - stained sections, 25 (14.8%) appeared to be consistent with aneurysmal dermatofibroma, 66 (39.1%) with cellular dermatofibroma, 36 (21.3%) with sclerosing dermatofibroma, and 22 (13.0%) with epithelioid dermatofibroma. Coexistence of two or more subtypes could be seen in 12 sections. There were also a few new variants, such as dermatofibroma with hyperplastic sweat duct (1 case) , deep dermatofibroma (3 cases) , dermatofibroma with epithelioid cells intermingled with hyperplastic collagen (1 case) . The duration of aneurysmal dermatofibroma varied from 7 months to 30 years, and most manifested as skin masses on the lower extremities. A relatively short course of disease was observed in patients with cellular dermatofibroma, who often visited a hospital several months after the onset, and cellular dermatofibroma was commonly observed on the extremities and frequently accompanied with itching and pain. The duration of sclerosing or atrophic dermatofibroma was usually long for years or decades, and it commonly occurred on the upper limbs without concomitant symptoms. Epithelioid dermatofibroma of varied durations had various clinical manifestations, frequently occurred on the lower limbs without concomitant symptoms. Conclusions The clinical and pathological manifestations of dermatofibroma are diverse. Different dermatofibroma lesions can share similar typical histopathological manifestations, and atypical pathological features can interfere with the diagnosis of dermatofibroma. Key words: Histiocytoma, benign fibrous; Skin manifestations; Pathological processes

Cellular Dermatofibroma: Clinicopathologic Review of 218 Cases of Cellular Dermatofibroma to Determine the Clinical Recurrence Rate

Cellular dermatofibromas, a variant of dermatofibroma, are reported to recur at rates of 26% to 50%. To determine whether there are distinct clinical or histological differences between cellular dermatofibromas that recur versus those that do not. To determine recurrence rates in a real-world clinical setting. A retrospective analysis of the medical records and skin biopsies of cellular dermatofibroma in the University of Utah Health system between December 2011 and 2016. Clinical and dermatopathological features were evaluated to find distinct differences between the cellular dermatofibromas that recurred compared with those that did not. There were no significant differences in histology between the primary lesions in recurrent and nonrecurrent cases. One factor that seemed to be associated with a greater likelihood of recurrence was an initial lesion size greater than 1 cm. The authors' data suggest that if the margins are involved on initial biopsy, there is a 10% chance of recurrence. This percentage is far less than the 26% to 50% reported in the past literature. If a patient presents with a cellular dermatofibroma larger than 1 cm and positive margins at initial biopsy, a careful discussion should be had between the provider and patient about the low risk of local recurrence.

Cellular dermatofibroma: A hyperkeratotic indurated plaque on the thigh.

Cellular dermatofibroma: A hyperkeratotic indurated plaque on the thigh.

Cellular dermatofibroma of post auricular region: An unusual presentation

Cellular dermatofibroma of post auricular region: An unusual presentation

Immunohistochemical Markers in Fibrohistiocytic Lesions

The distinction between dermatofibroma (DF), dermatofibrosarcoma protuberans (DFSP), and other benign and malignant cutaneous spindle cell lesions frequently requires immunohistochemical staining. CD34 and factor XIIIa are the most commonly used immunostains; however, they may exhibit aberrant expression and introduce the potential for misdiagnosis. There is some data supporting that p75 and S100A6 may be additional helpful immunohistochemical markers. We undertook a large case series examining the use of CD34 and factor XIIIa as well as p75 and S100A6 in DF, cellular DF, DFSP, indeterminate fibrohistiocytic lesion, and scar. As expected, CD34 stained DFSP, although it was usually negative in DF. Factor XIIIa was generally positive in DF and negative in DFSP. There were exceptions in both cases of DF and DFSP. S100A6 was routinely negative in all entities studied. P75 was negative in all cases except DFSP, approximately half of which showed weak and/or patchy positivity. We conclude that to date, CD34 and factor XIIIa remain the most reliable immunohistochemical markers for DF and DFSP.

Malignant dermatofibroma: clinicopathological, immunohistochemical, and molecular analysis of seven cases

Dermatofibroma (cutaneous fibrous histiocytoma) represents a common benign mesenchymal tumor, and numerous morphological variants have been described. Some variants of dermatofibroma are characterized by an increased risk of local recurrences, and there are a few reported metastasizing cases. Unfortunately, an aggressive behavior cannot be predicted reliably by morphology at the moment, and we evaluated the value of array-comparative genomic hybridization (CGH) in this setting. Seven cases of clinically aggressive dermatofibromas were identified, and pathological and molecular features were evaluated. The neoplasms occurred in four female and in three male patients (mean age was 33 years, range 2–65 years), and arose on the shoulder, buttock, temple, lateral neck, thigh, ankle, and cheek. The size of the neoplasms ranged from 1 to 9 cm (mean: 3 cm). An infiltration of the subcutis was seen in five cases. Two neoplasms were completely excised, whereas an incomplete or marginal excision was reported in the remaining cases. Local recurrences were seen in six cases (time to the first recurrence ranged from 8 months to 9 years). Metastases were noted between 3 months and 8 years after diagnosis in six patients. Two patients died of disease, and two patients are alive with disease. Histologically, the primary tumors showed features of cellular dermatofibroma (four cases), cellular/aneurysmal dermatofibroma (one case), atypical/cellular dermatofibroma (one case), and classical dermatofibroma (one case). Mitotic figures ranged from 3 to 25 per 10 high-power fields, and focal necrosis was present in five cases. Interestingly, malignant transformation from cellular dermatofibroma to an obvious spindle cell/pleomorphic sarcoma was seen in one primary and in one recurrent neoplasm. Five neoplasms showed chromosomal aberrations by array-CGH, suggesting that these changes may represent an additional diagnostic tool in the recognition of cases of dermatofibroma with a metastatic potential.

Cellular Neurothekeoma With Fascicular Growth Features Mimicking Cellular Dermatofibroma

Cellular neurothekeoma (CNT) is a benign cutaneous mesenchymal neoplasm. Most demonstrate a lobulated to micronodular architecture. Rarely, CNT demonstrates a predominantly fascicular growth pattern, without prominent sclerosis and thus can mimic cellular dermatofibroma (DF). Three CNT with a predominantly fascicular pattern were obtained. The clinicopathologic features and accompanying immunohistochemical stains were evaluated. All cases demonstrated a moderately cellular proliferation of epithelioid to spindle cells with pale to eosinophilic slightly granular cytoplasm, vesicular nuclei, and a single nucleolus arranged in a fascicular pattern with thick collagen bundles at the periphery (collagen trapping). One case had prominent epidermal hyperplasia. The neoplastic cells expressed NKI-C3, CD10, and micropthalmia transcription factor and lacked expression of factor XIIIa, S-100, epithelial membrane antigen, and CD34. Our cases showed an unusual pattern of CNT with a predominantly fascicular growth pattern, thickened collagen bundles at the periphery, and occasionally epidermal hyperplasia. The overlap with cellular DF is striking. The presence of plump to epithelioid cytomorphology with abundant cytoplasm, with focally prominent nucleoli; the presence of focal lobulated to micronodular growth pattern along with micropthalmia transcription factor positivity; and lack of factor XIIIa expression are helpful in distinguishing fascicular CNT from cellular DFs.

Amyloid Light Chain Deposition Associated with Dermatofibroma: Serendipity or Association?

Primary cutaneous amyloidosis, also known as nodular amyloidosis, is defined as deposition of amyloid light chain in the skin in the absence of a systemic cause of amyloidosis. Such amyloid is produced by a localized aggregate of clonal plasma cells. In contrast, secondary cutaneous amyloidosis is related to lesions such as squamous cell carcinoma, Bowen disease, basal cell carcinoma, and discoid lupus erythematosus, and has been shown in most cases to be derived from keratin epithelial elements. Herein, we present a unique case of nodular amyloidosis occurring in association with a cellular dermatofibroma.

Dermatofibrosarcoma Protuberans of the Vulva: A Clinicopathologic and Immunohistochemical Study of 13 Cases

Dermatofibrosarcoma protuberans (DFSP) is a low-grade sarcoma seldom seen in the vulva with only 29 cases reported. We present the clinicopathologic and immunohistochemical features of 13 such cases seen in our institution over a period of 29 years (1978 to 2007). Patient age ranged from 23 to 76 years (mean, 46 y). Twelve patients had a vulvar mass. One patient presented with a pigmented skin lesion. Tumor size ranged from 1.2 to 15 cm (median, 4 cm). Microscopically, all the cases showed typical features of DFSP. In 1 case, myxoid changes were also noted; 3 cases showed fibrosarcomatous transformation. Of interest, in 7 of our 13 cases, a variety of diagnoses, such as cellular dermatofibroma, cellular leiomyoma, neurofibroma, low-grade leiomyosarcoma, fibrosarcoma, low-grade malignant schwannoma, desmoplastic melanoma, cellular neurofibroma, and low-grade malignant peripheral nerve sheet tumor were initially considered. All 11 cases tested for CD34 were positive, whereas 7/9 cases, 8/9 cases, and 9/9 cases were positive for PDGFR-alpha, PDGFR-beta, and c-abl, respectively. All patients were initially treated with excisional biopsy, wide local excision, or radical vulvectomy. Local recurrences occurred in 7 cases. One patient also developed distant metastases. All recurrences were treated surgically; 1 patient also received chemotherapy and radiotherapy and another received imatinib (Gleevec). Follow-up data ranging from 2 to 444 months was available for all patients. Nine patients had no evidence of disease, 2 patients were alive with disease, 1 patient had died of disease, and 1 patient had died of other causes. DFSP affects women of a wide age range and has a propensity to recur locally. The frequent expression of PDGFR-alpha, PDGFR-beta, and c-abl in these cases agrees with the findings of other investigators and supports the use of imatinib (Gleevec) in cases that are recurrent or not amenable to surgery.

Morphometric analyses of elastic tissue fibers in dermatofibroma: clues to etiopathogenesis?

The etiopathogenesis of dermatofibroma (DF), a common benign fibrohistiocytic tumor, is debatable. The goal of this study was to ascertain the density of elastic tissue fibers in DF in an effort to investigate whether this provides an insight into its etiopathogenesis. Three groups comprising eight cellular DFs, eight paucicellular DFs and eight scars (control group) were stained with a modified Verhoeffs-van Gieson (without counterstain), and elastic fibers in three randomly selected fields within the lesional area/case semiquantitatively analyzed and examined in a blinded fashion. The mean density of elastic tissue fibers in cellular DF was 6.81 (1.38-15.89); in paucicellular DF, 2.46 (0.14-5.79) and in scar, 2.95 (0.97-10.69). Overall, significant differences in density of elastic tissue fibers were observed only between cellular DF and the other two groups (vs. paucicellular variant, p = 0.03 and vs. scar, p = 0.05). Morphological changes observed included thickness, clumping, elongation and waviness (cellular DF) and margination of elastic tissue fibers (paucicellular variant). While the jury still appears to be out regarding the etiopathogenesis of DF, the reduction in density of elastic tissue fibers in the paucicellular variant compared with its cellular counterpart lends credence to the concept of evolutionary stages of DF.

Cyclooxygenase‐2 expression in dermatofibroma and dermatofibrosarcoma protuberans

Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) occasionally resemble each other histologically but differ in histogenesis and biological behavior. This study sought to determine if these lesions can be differentiated by the quantity or quality of expression of cyclooxygenase-2 (COX-2), an enzyme associated with both reactive and neoplastic processes. Formalin-fixed and paraffin-embedded samples from 20 DFs and 20 DFSPs were stained immunohistochemically with antibodies directed against COX-2. Staining was evaluated semiquantitatively for percentage and intensity using a three-tiered system. DFs were graded and analyzed by cellularity. Findings within the tumors were compared with fibrocyte staining in adjacent tissue. The results were analyzed. Nineteen DFs (95%) and 15 DFSPs (75%) were immunopositive for COX-2; this difference was not statistically significant. Highly cellular DFs showed more widespread (p = 0.0039; r = 0.614) and more intense (p = 0.0586; r = 0.429) staining than less cellular DFs and more prominent staining in adjacent fibroblasts (p = 0.044; r = 0.608). COX-2 immunostaining does not distinguish DFs from DFSPs. However, the enzyme is expressed more widely and more intensely in more cellular, possibly younger, DFs. The prominent expression of COX-2 in DFSP may have clinical implications for treatment with COX-2 inhibitors in tumors that are not amenable to surgery.

Dermatofibrome rétro-auriculaire chez un enfant simulant une tumeur maligne

Dermatofibroma represents one of the commonest benign soft tissue tumours, and its diagnosis is usually straightforward if classical clinicopathologic features are evident. It occurs frequently on the extremities and trunk, often in young adults during the 3(rd) and 4(th) decades. We report a peculiar case of an aggressive cellular dermatofibroma in a child that simulated a malignant tumour. Our aim is to discuss the differential diagnosis.An 8-year-old boy presented with a retroauricular tumour. Clinically, the lesion, 2 cm in diameter, was located in the left retroauricular region. It was nodular, erythematous, infiltrating the underlying tissue with an anterior spread leading to an amputation of the auricular lobule and a retraction of the tragus. Computerized axial tomography revealed a local tissular thickening extending in soft tissues without any bone involvement. A malignant lesion was initially suspected. A biopsy was performed. It was followed by a surgical resection. The lesion had the full microscopic characteristics of a cellular dermatofibroma.Dermatofibroma is one of the major differential diagnosis of nodular cutaneous tumours in children that simulate malignancy. Histologic examination with immunohistochemical study is essential for diagnosis.

Apolipoprotein D in CD34-positive and CD34-negative cutaneous neoplasms: a useful marker in differentiating superficial acral fibromyxoma from dermatofibrosarcoma protuberans

More recent techniques to characterize the genetic profile of soft-tissue tumors include the use of gene arrays. Using this technique, Apolipoprotein D (Apo D), a 33-kDa glycoprotein component of high-density lipoprotein, has been found to be highly expressed in dermatofibrosarcoma protuberans. To corroborate these results, we sought to ascertain the utility of Apo D by investigating its sensitivity and specificity in a variety of CD34-positive and CD34-negative cutaneous neoplasms including superficial acral fibromyxoma, sclerotic fibromas, and cellular dermatofibromas. Of interest, we found absence of Apo D expression in all four cases of superficial acral fibromyxoma. Of the remaining CD34-positive lesions, Apo D expression was noted in 35/36 (97%) cases of dermatofibrosarcoma protuberans, 3/5 (60%) giant-cell fibroblastomas, 4/4 (100%) sclerotic fibromas, 8/8 (100%) neurofibromas, and 1/1 (100%) solitary fibrous tumor. Of the CD34-negative lesions, Apo D expression was noted in 2/22 (9%) regular dermatofibroma, 23/45 (51%) cellular dermatofibroma, 10/10 (100%) malignant fibrous histiocytoma, 9/10 (90%) atypical fibroxanthoma, 7/8 (86%) cellular neurothekeoma, 9/9 (100%) malignant melanoma, 8/8 (100%) melanocytic nevi (100%), 0/2 superficial angiomyxoma, 0/15 fibromatosis, 0/1 nodular fasciitis, and 1/2 (50%) desmoplastic fibroblastomas. In summary, our findings indicate that Apo D expression is not specific to dermatofibrosarcoma protuberans. Its principal use as an immunohistochemical adjunct lies in its utility in differentiating superficial acral fibromyxoma from dermatofibrosarcoma protuberans. Although strong positive staining of Apo D in a markedly atypical fibrohistiocytic lesion is suggestive of atypical fibroxanthoma and/or malignant fibrous histiocytoma, further studies with the inclusion of other atypical spindled cell neoplasms are required to conclusively prove the same.

A study of CD117 expression in dermatofibrosarcoma protuberans and cellular dermatofibroma

Dermatofibrosarcoma protuberans (DFSP) is a relatively uncommon spindle cell tumor of the skin. It is locally aggressive and can be a therapeutic challenge. There are case reports of partial response of DFSP to the tyrosine kinase inhibitor STI571 (Imatinib), despite the reported negativity of the tumor cells for CD117. At least one publication reported focal CD117 positivity of DFSP cells, and we would like to clarify the issue. Cellular dermatofibroma (CDF) can mimic DFSP, but typical cases are easily differentiated from DFSP by their staining pattern for CD34 and factor 13a. We also report our experience with CD117 staining of typical CDFs. Thirty-seven cases of clear-cut DFSP and 13 cases of clear-cut CDF were retrieved from the archives of Sunnybrook Health Sciences Center between 2000 and 2005. All DFSPs were CD34 (+), factor 13a (-) and CD117 (-). All CDFs were factor 13a (+), CD34 (-) and CD117 (-). Our study on a relatively large number of cases confirms the negativity of DFSP and CDF for CD117. Therefore, if adjuvant therapy is attempted with drugs such as STI571 (Imatinib), the eligibility of patients should not be based on immunohistochemical assessment of CD117 expression.

Metastasizing dermatofibroma in lung

Benign dermatofibroma is very common skin tumor and can very rarely metastasize. We report a case of metastasizing dermatofibroma on a 36-year-old woman who presented multiple bilateral lung nodules. She underwent incisional biopsy for cellular dermatofibroma of the right shoulder 7 years ago. Chest computed tomographic scanning shows multiple nodules in both lung fields. Segmental and wedge resections were done. Grossly, the masses were hemorrhagic cysts. Microscopically, there were dilated cystic airspaces. The airspaces were lined by respiratory and metaplastic squamous epithelium with underlying layers of fibrohistiocytic spindle cells with storiform and fascicular pattern. The tumor cells stained for CD68 and CD10. The lung mass shows same histologic features with skin lesion.

Myofibrosarcoma Treated with Mohs Micrographic Surgery

BACKGROUND Myofibrosarcoma is a rare malignant mesenchymal tumor composed predominantly of differentiated myofibroblasts. These tumors occur in both children and adults alike and are most commonly located on the head and neck. Recurrences rates range from 44% to 75%, and metastatic disease has been reported in up to 44% of cases. OBJECTIVE The objective was to present a case of a myofibrosarcoma treated with Mohs micrographic surgery and discuss the use of ultrastructural evaluation in the diagnosis of this rare tumor. METHODS A 31-year-old African American woman who presented to the Emory University Dermatologic Surgery Clinic with a 4-month history of a 2.5 × 2.5-cm indurated firm painful right upper lateral thigh nodule. A prior biopsy revealed a proliferation of somewhat bland spindled cells with large zones of necrosis with prominent mitotic figures, changes compatible with a cellular dermatofibroma. Because the lesion exhibited clinically suspicious characteristics such as rapid growth and deep infiltration, the patient was subsequently referred to Emory for further evaluation. There was no evidence of lymphadenopathy and a chest X-ray was unremarkable. RESULTS A two-staged (five and four sections, respectively) uneventful Mohs micrographic surgery procedure was performed resulting in a defect measuring 3.5 × 3.5 × 1.0 cm. Primary closure was achieved with no complication, and the final scar measured 10 cm. Because of the suspicious clinical behavior of this tumor debulking specimen was sent for permanent section. Histopathologic interpretation of these sections was consistent with a fibrosarcoma with myofibroblastic differentiation. No clinical recurrence noted after 14-month follow-up. CONCLUSION Mohs micrographic surgery is a technique that has been shown to provide superior cure rates in the treatment of many mesenchymal tumors. Here, we report the first case of myofibrosarcoma treated with Mohs micrographic surgery. Myofibrosarcoma is a rare but aggressive tumor that can be difficult to distinguish from other somewhat less aggressive malignancies such as dermatofibrosarcoma protuberans or malignant fibrous histiocytoma. Specific histopathologic criteria are reviewed. We recommend including Mohs micrographic surgery in the armamentarium for the treatment of this rare tumor.

Myofibrosarcoma Treated with Mohs Micrographic Surgery

Myofibrosarcoma is a rare malignant mesenchymal tumor composed predominantly of differentiated myofibroblasts. These tumors occur in both children and adults alike and are most commonly located on the head and neck. Recurrences rates range from 44% to 75%, and metastatic disease has been reported in up to 44% of cases. The objective was to present a case of a myofibrosarcoma treated with Mohs micrographic surgery and discuss the use of ultrastructural evaluation in the diagnosis of this rare tumor. A 31-year-old African American woman who presented to the Emory University Dermatologic Surgery Clinic with a 4-month history of a 2.5 x 2.5-cm indurated firm painful right upper lateral thigh nodule. A prior biopsy revealed a proliferation of somewhat bland spindled cells with large zones of necrosis with prominent mitotic figures, changes compatible with a cellular dermatofibroma. Because the lesion exhibited clinically suspicious characteristics such as rapid growth and deep infiltration, the patient was subsequently referred to Emory for further evaluation. There was no evidence of lymphadenopathy and a chest X-ray was unremarkable. A two-staged (five and four sections, respectively) uneventful Mohs micrographic surgery procedure was performed resulting in a defect measuring 3.5 x 3.5 x 1.0 cm. Primary closure was achieved with no complication, and the final scar measured 10 cm. Because of the suspicious clinical behavior of this tumor debulking specimen was sent for permanent section. Histopathologic interpretation of these sections was consistent with a fibrosarcoma with myofibroblastic differentiation. No clinical recurrence noted after 14-month follow-up. Mohs micrographic surgery is a technique that has been shown to provide superior cure rates in the treatment of many mesenchymal tumors. Here, we report the first case of myofibrosarcoma treated with Mohs micrographic surgery. Myofibrosarcoma is a rare but aggressive tumor that can be difficult to distinguish from other somewhat less aggressive malignancies such as dermatofibrosarcoma protuberans or malignant fibrous histiocytoma. Specific histopathologic criteria are reviewed. We recommend including Mohs micrographic surgery in the armamentarium for the treatment of this rare tumor.

Smooth-muscle proliferation in dermatofibromas.

Although a variety of epithelial changes have been associated with dermatofibromas, mesenchymal proliferations induced by dermatofibromas appear to be rare. We report three dermatofibromas that were associated with proliferation of smooth muscle within the adjacent dermis. The lesions ranged from a large, densely cellular dermatofibroma with "monster cells" to a sparsely cellular, fibrous lesion. In all three cases, the smooth muscle could be discerned in hematoxylin- and -eosin-stained sections, because its presence caused an interruption in the pattern of reticular dermal collagen bundles with blunt-ended vesicular nuclei. Well-formed fascicles were apparent in immunoperoxidase-stained sections using antisera to muscle-specific actin (HHF-35) and desmin. The smooth muscle failed to stain with either antisera to S-100 protein or Leu-7, precluding determination of whether it immunophenotypically resembled vascular or pilar smooth muscle. We believe that the smooth-muscle proliferation in our cases was induced by the spindled cells of dermatofibroma, just as epithelial changes in association with dermatofibroma are. We further believe that it is most likely of vascular derivation, based on a previous report of angioleiomyoma arising in a dermatofibroma as well as the continuity of fascicles of smooth muscle with a thick-walled vessel in one of our cases. Less likely explanations include collisions between dermatofibromas and leiomyomas or divergent differentiation in a proliferation arising from primitive mesenchymal cells.

Atrophic dermatofibroma and dermatofibrosarcoma protuberans

Dermatofibroma and dermatofibrosarcoma protuberans usually are seen as firm nodules in the skin. We have observed several patients, all female, with an atrophic or depressed lesion on the chest or back. When biopsy was done, the biopsy punch was often noted to sink into the lesion. In each case the biopsy specimen showed a cellular dermatofibroma or dermatofibrosarcoma protuberans. The correct diagnosis was rarely suspected clinically. This uncommon clinical presentation may be related to the marked cellularity of the fibrous tumors in this series.