Fibrohistiocytic skin tumors

The fibrohistiocytic tumors of the skin are a heterogeneous group of dermal/subcutaneous mesenchymal neoplasms which show fibroblastic, myofibroblastic and histiocytic (macrophage‐like) differentiation, often one beside the other in the same tumor. “Fibrohistiocytic” means in this context the morphologic similarity of the cells with fibroblasts and histiocytes. The WHO classification of 2005 includes the following entities as fibrohistiocytic tumors of the skin: Benign: 1. Fibrous histiocytoma (FH)/(synonymous: Dermatofibroma. Variants of FH: 1a. cellular fibrous histiocytoma, 1b. atypical (pseudosarcomatous) fibrous histiocytoma, 1c. aneurysmatic fibrous histiocytoma, 1d. epithelioid fibrous histiocytoma; 2. dermatomyofibroma; 3. (juvenile) xanthogranuloma. Intermediate: 4. plexiform fibrohistiocytic tumor; 5. dermatofibrosarcoma protuberans; 6. atypical Fibroxanthoma. Malignant: 7. malignant fibrous histiocytoma. All these entities are reviewed in this paper with particular attention devoted to differential diagnostic considerations.     

Cutaneous and subcutaneous fibrohistiocytic tumors of intermediate malignancy: an update

The fibrohistiocytic tumors of intermediate malignancy are uncommon mesenchymal tumors, which typically occur in the skin and subcutis and which may pose significant problems for the dermatopathologist. This article reviews the clinical, histopathologic, and genetic features of dermatofibrosarcoma protuberans, giant cell fibroblastoma, angiomatoid (malignant) fibrous histiocytoma, plexiform fibrous histiocytoma, and soft tissue giant cell tumor (of low malignant potential). The differential diagnosis of these tumors with a variety of benign and fully malignant cutaneous soft tissue neoplasms is discussed.     

Mitosis in dermatofibroma: a worrisome histopathologic sign that does not necessarily equal recurrence

Background:  High mitotic rate is a worrying histopathologic feature that pathologists occasionally face when diagnosing benign fibrous histiocytoma (BFH), that otherwise seem to be benign. The clinical significance of this histologic feature has not been completely studied, because no studies on large series of BFH have been carried out, concerning mitotic rate as the only worrisome morphologic sign, in relation with recurrence.
Methods:  In order to study how common a high mitotic rate is in BFH, which do not present any other worrisome morphological signs, we studied 200 cases from our archives and counted the number of mitosis per 10 high power fields (HPFs) in all of them. We selected those cases that had a mitotic number of 4 or more mitosis per 10 HPF. We also performed the immunohistochemical study with MIB-1 antibody (DakoCytomation, Denmark A/S). The clinical histories of the patients were also reviewed, in order to find out if there had been any recurrence.
Results:  Four BFH presented four or more mitosis in ten HPF. None of them had presented any recurrence or metastasis, and the follow-up time was at least for 71 months.
Conclusions:  We conclude that common BFH can occasionally present a high mitotic rate and still show a benign behavior.     

Benign fibrous histiocytoma with osteoclast-like giant cells in an infant

Abstract:  Benign fibrous histiocytoma is a common soft tissue tumor that usually occurs in adults and is relatively rare in childhood. This report describes a 7-month-old Caucasian boy with an enlarging firm congenital nodule on his occipital scalp. Histologic analysis revealed a benign fibrous histiocytoma with osteoclast-like giant cells. Benign fibrous histiocytoma with osteoclast-like giant cells is a rare histologic variant.     

Aneurysmal Benign Fibrous Histiocytoma with Atrophic Features

Aneurysmal benign fibrous histiocytoma is an uncommon pathologic variant of dermatofibroma. In addition to the features of a typical dermatofibroma, it has large cleft-like or cavernous blood-filled spaces with numerous hemosiderin pigments. It should be differentiated from angiomatoid malignant fibrous histiocytoma, malignant melanoma, and vascular tumors such as Kaposi''s sarcoma and angiosarcoma. Atrophic dermatofibroma is also a rare variant of dermatofibroma, and the combination of aneurysmal and atrophic features is rarer still. We report a case of aneurysmal benign fibrous histiocytoma with atrophic features in a 27-year-old male who had a grayish-brown atrophic patchy lesion on his back for 2 years.     

Dermatofibroma with osteoclast-like giant cells.

Dermatofibroma (DF), or cutaneous fibrous histiocytoma, is a common cutaneous tumor with many variants that may arise from alterations in the morphology and composition of its various components. One type that has not received much attention is DF with osteoclast-like giant cells. Two cases of this rare tumor are described. The importance of this tumor lies in the possible histologic confusion with a variety of benign and malignant neoplasms, including giant cell tumor of tendon sheath, giant cell tumor of bone, and giant cell reparative granuloma.     

A Case of Subcutaneous Malignant Fibrous Histiocytoma Circumscribed by Fibrous Tissue

We report a case of malignant fibrous histiocytoma (MFH) located in the subcutaneous tissue on the right axilla. We excised the tumor sufficiently beyond the clinical margin. It was pathologically diagnosed as a storiform-pleomorphic type of malignant fibrous histiocytoma almost completely circumscribed by fibrous tissue, including fascicles of fibroblasts; this is a rare histological picture. The tumor has not recurred for three years. Although MFH frequently undergoes metastasis, the circumscribed-type subcutaneous MFH characteristic of superficiality and of histologically well-defined structure seems to have a relatively more favorable prognosis after adequate radical excision.     

Metastasizing soft tissue tumor of light damaged skin: atypical fibroxanthoma or malignant fibrous histiocytoma?

A 86-year-old female patient presented with a ca. walnut-sized, centrally ulcerated preauricular tumor on the right side as well as a firm submandibular lymph node. Histology disclosed a soft-tissue tumor breaking into the lymph node consisting partly of fibroblast-like and partly of histiocyte-like cells. Clinical and histological criteria speak for both an atypical fibroxanthoma (AFX) as well as a malignant fibrous histiocytoma (MFH). A differentiation into two entities does not appear appropriate in our opinion. As the term "AFX" is classified as a benign tumor, "metastasizing AFX" (mAFX) should be considered a special form of MFH or be diagnosed as such, respectively.     

Pedunculated hemangiopericytoma-like tumor: peculiar fibroepithelial polyp or fibrous histiocytoma variant

Abstract:  Pathologists are continually challenged with the difficult task of discriminating between innocuous disease processes and potentially malignant entities. Apropos of this concern, we present a series of three cutaneous polypoid lesions that simulated fibroepithelial polyp, yet upon close scrutiny yielded histologic features of solitary fibrous tumor (SFT) or hemangiopericytoma. These pedunculated lesions showed a storiform pattern of spindled cells with interspersed gaping vascular channels reminiscent of SFT or hemangiopericytoma. Interestingly, the immunohistochemical staining profile of these lesions was negative for CD34 and positive for bcl-2 and factor XIIIa. These findings were discordant with SFT and suggest a relationship with fibrous histiocytoma. We propose that this entity represents a hitherto described variant of fibrous histiocytoma known as pedunculated hemangiopericytoma-like fibrous histiocytoma.     

Myxofibrosarcoma associated with anetoderma

BACKGROUND: Association of malignant cutaneous tumor and secondary anetoderma is rare. Secondary anetoderma in myxofibrosarcoma has not been described to date. We report a case below. CASE REPORT: A 80-year-old woman presented with a 40 x 40 mm, round, flesh-colored lesion on her left buttock. Physical examination showed a soft, protuberant lesion, without firm underlying subcutaneous mass. Pathologic examination of the surgical specimen revealed a myxofibrosarcoma, with focal loss of elastic fibers in the overlying dermis. There was no evidence of systemic involvement. One year later, she developed a recurrent tumor at the same site, with similar clinical presentation, which was treated by broad excision. DISCUSSION: Secondary anetoderma is usually seen in association with cutaneous infections and benign skin tumors. An anetodermic presentation of myxofibrosarcoma has not been reported to our knowledge. Myxofibrosarcoma (formerly referred to as myxoid malignant fibrous histiocytoma) is characterized by an abundant myxoid background in at least one half of the tumor. The tumor recurs in almost two-thirds of cases and metastasizes in one-fourth. Our case confirms that a unique, acquired anetodermic lesion can reveal a malignant tumor. A large deep biopsy should be performed systematically when this variety of anetoderma is observed.     

Tissue cultures of benign and malignant fibrous histiocytomas: SEM observations

Four dermatofibromas (DF), 2 dermatofibrosarcomata protuberans (DFSP), 2 atypical fibroxanthmas of the skin (AFX), and one malignant fibrous histiocytoma (MFH) were studied by explant culture technique and scanning electron microscopy. Differences in the cellular atypism, phagocytic activity and motility were observed between histiocyte-like cells extending from a DF and DFSP group and an AFX and MFH group. Such cytological characteristics was maintained during in vitro transformation of the cells into fibroblastic cells. It was concluded that culture behaviors of the cells from each tumor group correlated well with in vivo growth and histologic features. We feel that examination of m vitro morphology of fibrous histiocytomas may prove useful in arriving at a correct diagnosis.     

Case for diagnosis

We report the case of an 11-year-old male patient with a histopathological and immunohistochemical diagnosis of dermatofibroma with an atypical clinical presentation on the right forearm. Although dermatofibroma is considered a benign skin tumor, some of its differential diagnoses, such as dermatofibrosarcoma protuberans and malignant fibrous histiocytoma, are truly aggressive. Lesions with atypical clinical aspects and topology associated with specific histopathological variants are some of the criteria for complete tumor excision.     

Benign fibrous histiocytoma of the eyelid with an unusual clinical presentation

Benign fibrous histiocytoma is a common soft tissue tumor that can be deep or superficially located. Although the deep type of fibrous histiocytoma has a predilection for the orbit, the eyelids are an unusual location for the cutaneous type. A 42-year-old woman had bilateral yellowish nodular masses of the eyelids for two years. Pathological examination after excision revealed benign fibrous histiocytoma. Our case is an unusual clinical presentation of cutaneous fibrous histiocytoma as well as a rare location such as the eyelids.     

Immunohistochemical study of membrane type-matrix metalloproteinases (MT-MMPs) and matrix metalloproteinase-2 (MMP-2) in dermatofibroma and malignant fibrous histiocytoma

Matrix metalloproteinases (MMPs) play an important role in tumor invasion and metastasis. Enhanced expression of matrix metalloproteinase-2 (MMP-2) has been demonstrated in dermatofibroma (DF) and malignant fibrous histiocytoma (MFH). MMP-2 has been shown to be activated by membrane-type MMPs (MT-MMPs). To study the role of MT-MMP in the activation of MMP-2, skin specimens of DF (five cases) and MFH (three cases) were immunohistochemically studied using in situ zymography and the antibodies against matrix metalloproteinase-2 (MMP-2) and membrane type 1-3-MMPs (MT1-3-MMPs). Both MMP-2 activity and its expression were significantly activated in the tumor cells in DF and MFH. Anti-MT2-MMP strongly reacted with tumor cells of all cases of DF and MFH, whereas anti-MT1 or 3-MMP antibody showed a weak reaction in some cases of DF and MFH. Double immunofluorescence labeling demonstrated that the immunoreactive cells with anti-MMP-2 antibody in DF and MFH consistently reacted with anti-MT2-MMP antibody. The results suggest that the activation of MMP-2 in the benign and malignant fibrous tumors is related to the activation of MT-MMPs.     

Immunohistochemistry of dermatofibromas and benign fibrous histiocytomas

Dermatofibromas (DF) are common, benign skin tumors composed predominantly of cells having elongated nuclei and very scant cytoplasm (i.e., fibroblasts) and capillaries in a collagenous stroma. Some authors distinguish DF from benign fibrous histiocytomas (BFH), which are composed of cells with round to oval nuclei and abundant cytoplasm (i.e., histiocytes). In general, this group of tumors expresses factor XIIIa but not the antigen recognized by MAC 387. However, immunohistochemical differences specifically between DF and BFH have not been reported.
We have studied the immunophenotype of 23 lesions having morphologic features predominantly either of DF (17 cases) or BFH (6 cases) using antibodies against desmin (muscle marker), α-smooth-muscle actin (muscle and myofibroblast marker), CD68 and HAM56 antigen (markers commonly expressed by macrophages, so called "histiocytic" markers), CD34 (a marker present in hematopoietic, vascular, and occasional dermal dendritic cells), and factor XIIIa (a transglutaminase present in many cells including dermal dendrocytes). Many spindle-shaped cells expressed a-smooth-muscle actin while many large, round cells expressed the histiocytic markers. However, most lesions expressed at least focally both α-smooth-muscle actin and "histiocytic" markers. Thus a clear-cut distinction between DF and BFH could not be made based on immunophenotype alone. Additionally, the prominent α-smooth-muscle actin immunoreactivity and desmin non-reactivity suggests myofibroblastic differentiation in the spindle-cell regions of these tumors, and indicates that expression of a-smooth-muscle actin cannot be used as definitive proof of muscle differentiation in spindle-cell tumors. We conclude that DF and BFH are not discrete entities, but represent polar expressions of one nosologic entity exhibiting both myofibroblastic and "histiocytic" differentiation.     

A rare low-grade malignant scalp tumor. Atypical fibroxanthoma

A 79-year-old patient presented with an asymptomatic scalp tumor which had grown over the past 9 months. Based on clinical, histological and immunohistochemical staining, we made the diagnosis of an atypical fibroxanthoma (AFX). AFX is a rare tumor, but important in the differential diagnosis of other scalp tumors. The routine histological staining allows one to identify a malignant fibrous histiocytoma, while a spindle-cell malignant melanoma can be excluded with immunohistochemical staining. An anaplastic squamous cell carcinoma cannot always be separated with completed certainty from atypical fibroxanthoma. AFX is a low-grade malignant tumor and most cases behave in a benign fashion. After complete excision, we recommend follow-up for a number of years because of the possibility of local recurrence.     

硬皮病样皮肤转移性恶性纤维组织细胞瘤1例

报告1例硬皮病样皮肤转移性恶性纤维组织细胞瘤。患者男,60岁。面颊及颈部皮肤硬韧1个半月。病理检查示:真皮浅中层胶原纤维间见散在或密集的类似成纤维细胞样细胞、组织细胞样细胞浸润,细胞核大而深染,呈长梭形及圆形,小血管腔内也见核大深染的细胞及多核巨细胞。免疫组化示:CD68(+),CD34,CK,SMA均阴性。诊断:皮肤转移性恶性纤维组织细胞瘤。     

Benign fibrous histiocytoma of the foot: a literature review and case report

A rare case of benign fibrous histiocytoma involving the foot of a sixty-three-year-old white man is presented, with a review of the literature. The histopathologic appearance of benign fibrous histiocytoma, differential diagnosis, and surgical management are discussed. Fibrous histiocytomas are characteristically nonencapsulated tumors composed of a mixture of fibroblastic and histiocytic cells arranged in a storiform or cartwheel pattern.