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Several histologic variants of dermatofibroma are described below. Note that not all variants are mutually exclusive and that more than one type may be present within the same lesion. Therefore, these variants probably only describe unusual features of the dermatofibroma rather than distinctive pathologies. That said, understanding these variants is helpful to the clinician, as certain features suggest a more aggressive clinical course and therefore require special attention, for example ensuring adequate excision<\/span> margins and consideration of ongoing monitoring.<\/p>\nThe term fibrous histiocytoma can be used interchangeably with dermatofibroma or to describe a dermatofibroma with a prominent storiform pattern.<\/p>\n
<\/span>\nCellular<\/span> dermatofibroma<\/span><\/h3>\nCompared to the usual dermatofibroma, the cellular dermatofibroma has a higher probability of reappearance<\/span> next split and metastasis<\/span> is reported. Histologically<\/span>, there is increased cellularity with a vortex swirl pattern (Figures 3,4). Peripheral<\/span> Collagen entrapment is less prominent in this variant. There may be an increase mitosis<\/span> and extension to subcutaneous<\/span> fat, which are associated with more aggressive behavior. Approximately 10% of cases show central necrosis<\/span>.<\/p>\nCellular dermatofibroma can resemble dermatofibrosarcoma protruding, which can be differentiated<\/span> due to its larger size, increased mitosis and marked involvement of subcutis<\/span>. CD34 is positive in dermatofibrosarcoma protuberans and is generally negative in dermatofibroma, although the cell variant may have focal<\/span> positivity, especially in the periphery of the lesion. A study of clone<\/span> karyotype<\/span> Dermatofibroma abnormalities found that cellular dermatofibromas were more likely to have karyotype abnormalities than common dermatofibromas.<\/p>\n\n<\/span>Cellular dermatofibroma pathology<\/span><\/h5>\n<\/section>\n\n\n
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figure 3<\/p>\n
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Figure 4<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>\nEpithelioid<\/span> dermatofibroma<\/span><\/h3>\nEpithelioid dermatofibroma is a well-recognized variant of dermatofibroma that can be confused with other benign and evil one<\/span> Mesenchymal lesions. The recent discovery of common ALK-1 translocation<\/span> some authorities have believed that this is better considered a distinct entity rather than a form of dermatofibroma. Clinically it is distinctive, it appears as a polypoid red nodule. Like common dermatofibromas, epithelioid dermatofibromas are most commonly found on the leg. However, they can be found in unusual places, including on the tongue.<\/p>\nSections through the epithelioid dermatofibroma show a central location, circumscribed<\/span> tumor underlying a epidermal<\/span> collarette The tumor is composed of cells arranged in sheets and sometimes a stormy pattern. Individual cells show epithelioids morphology<\/span> with abundant eosinophilic<\/span> cytoplasm<\/span> with round vesicular<\/span> nuclei<\/span> and prominent nucleoli (Figures 5, 6). Cells may be noticeably enlarged and show some nuclear<\/span> atypia<\/span> and mitosis. There is often an associate inflammatory<\/span> cell infiltrate<\/span> which can be useful for diagnosis.<\/p>\nDifferential diagnosis<\/span> includes other epithelioid tumors:<\/p>\n\n- \nAmelanotic<\/span> melanoma<\/span> - similar large epithelioid cells but generally show more pleomorphism<\/span> and epidermal involvement, and it is S100 positive.<\/li>\n
- Epithelioid sarcoma<\/span> – granuloma<\/span>cluster type with necrosis, more atypia, curb<\/span>+.<\/li>\n
- Other dermal epithelioid tumors: Immunohistochemical studies can help to exclude epithelioid vascular<\/span>, smooth muscle and histiocytic<\/span> tumors<\/li>\n<\/ul>\n\n
<\/span>Epithelioid dermatofibroma pathology<\/span><\/h5>\n<\/section>\n\n\n
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Figure 5<\/p>\n
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Figure 6<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Aneurysmal dermatofibroma<\/span><\/h3>\nThe clinical presentation of aneurysmal dermatofibroma is a rapidly growing blue-brown nodule. Periods of rapid growth are secondary to hemorrhage<\/span> within the injury. These tumors have a high recurrence rate and there is a report of aneurysmal dermatofibroma with regional lymph node<\/span> intervention.<\/p>\nHistologically, there are cleft<\/span>-I like it hemorrhagic<\/span> spaces within the center of the aneurysmal dermatofibroma that mimic vessels but lack endothelial<\/span> covering. The tumor itself tends to be quite cellular (Figure 7, 8). Hemosmosin<\/span> statement<\/span> It can be an additional feature. Aneurysmal dermatofibroma can be mistaken for a vascular tumor, however, keys to diagnosis include the surrounding features of the dermatofibroma, and endothelial cell markers are positive only in normal vessels and not in aneurysmal spaces.<\/p>\n\n<\/span>Aneurysmal pathology of dermatofibroma<\/span><\/h5>\n<\/section>\n\n\n
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Figure 7<\/p>\n
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Figure 8<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>\nAtypical<\/span> dermatofibroma<\/span><\/h3>\nAtypical dermatofibroma is also known as monster cell dermatofibroma or pseudosarcomatous dermatofibroma. There are focal areas within a common dermatofibroma consisting of large polymorphous<\/span> cells with large nucleoli ("monster cells") (Figures 9, 10).<\/p>\nAtypical dermatofibroma can be aggressive with rare reports of metastasis and death. However, many of these cases were described before modern immunohistochemical studies were available and can now be reclassified as sarcomas<\/span>.<\/p>\n\n<\/span>Atypical dermatofibroma pathology<\/span><\/h5>\n<\/section>\n\n\n
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Figure 9<\/p>\n
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Figure 10<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>Hemosiderotic dermatofibroma