Dermatofibroma pathology

Introduction

Dermatofibroma is common benign tumor Also known as fibrous histiocytoma. There is debate as to whether the dermatofibroma has a reagent or neoplastic origin. The clinic injury it's a firm tan brown nodule most commonly found on the legs. A number of histological there are variants

Histology dermatofibroma

Dermatofibromas are dermal tumors characterized by poorly defined proliferation fibrohistiocytic cells within the dermis with an overlay grenz zone savings (figure 1). At the periphery of the injury, there is entrapment of collagen (Figure 2). The overlying epidermis may be acanthotic with magnification basal cap pigmentation. Sometimes there basaloid induction of the epidermis (figure 1, arrow) which may resemble a small basal cell carcinoma or benign follicular tumors

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 margins and consideration of ongoing monitoring.

The term fibrous histiocytoma can be used interchangeably with dermatofibroma or to describe a dermatofibroma with a prominent storiform pattern.

Cellular dermatofibroma

Compared to the usual dermatofibroma, the cellular dermatofibroma has a higher probability of reappearance next split and metastasis is reported. Histologically, there is increased cellularity with a vortex swirl pattern (Figures 3,4). Peripheral Collagen entrapment is less prominent in this variant. There may be an increase mitosis and extension to subcutaneous fat, which are associated with more aggressive behavior. Approximately 10% of cases show central necrosis.

Cellular dermatofibroma can resemble dermatofibrosarcoma protruding, which can be differentiated due to its larger size, increased mitosis and marked involvement of subcutis. CD34 is positive in dermatofibrosarcoma protuberans and is generally negative in dermatofibroma, although the cell variant may have focal positivity, especially in the periphery of the lesion. A study of clone karyotype Dermatofibroma abnormalities found that cellular dermatofibromas were more likely to have karyotype abnormalities than common dermatofibromas.

Epithelioid dermatofibroma

Epithelioid dermatofibroma is a well-recognized variant of dermatofibroma that can be confused with other benign and evil one Mesenchymal lesions. The recent discovery of common ALK-1 translocation 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.

Sections through the epithelioid dermatofibroma show a central location, circumscribed tumor underlying a epidermal collarette The tumor is composed of cells arranged in sheets and sometimes a stormy pattern. Individual cells show epithelioids morphology with abundant eosinophilic cytoplasm with round vesicular nuclei and prominent nucleoli (Figures 5, 6). Cells may be noticeably enlarged and show some nuclear atypia and mitosis. There is often an associate inflammatory cell infiltrate which can be useful for diagnosis.

Differential diagnosis includes other epithelioid tumors:

• Amelanotic melanoma - similar large epithelioid cells but generally show more pleomorphism and epidermal involvement, and it is S100 positive.
• Epithelioid sarcoma – granulomacluster type with necrosis, more atypia, curb+.
• Other dermal epithelioid tumors: Immunohistochemical studies can help to exclude epithelioid vascular, smooth muscle and histiocytic tumors

Aneurysmal dermatofibroma

The clinical presentation of aneurysmal dermatofibroma is a rapidly growing blue-brown nodule. Periods of rapid growth are secondary to hemorrhage within the injury. These tumors have a high recurrence rate and there is a report of aneurysmal dermatofibroma with regional lymph node intervention.

Histologically, there are cleft-I like it hemorrhagic spaces within the center of the aneurysmal dermatofibroma that mimic vessels but lack endothelial covering. The tumor itself tends to be quite cellular (Figure 7, 8). Hemosmosin statement 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.

Atypical dermatofibroma

Atypical dermatofibroma is also known as monster cell dermatofibroma or pseudosarcomatous dermatofibroma. There are focal areas within a common dermatofibroma consisting of large polymorphous cells with large nucleoli ("monster cells") (Figures 9, 10).

Atypical 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.

Hemosiderotic dermatofibroma

The hemosiderotic dermatofibroma may show extensive hemosiderin deposition (Figure 11). Clinically, these can be pigmented and can mimic melanoma.

Lipidized dermatofibroma

Lipidized dermatofibroma is also known as "ankle-like" dermatofibroma due to a predilection for the lower leg Histologically, sparkling histiocytes predominate with marked hyalinization of collagen-like amyloid (figure 12).

Fibrocollagen dermatofibroma

Fibrocollagen dermatofibroma has a prominent storiform or swirl pattern, with a predominance of collagen and fibroblasts-like cells (Figures 13, 14). This subtype appears to be more common in rare cases of disseminated dermatofibroma seen in immunosuppressed patients

Clear cell dermatofibroma

Clear cell dermatofibroma has a benign behavior. Some experts consider it to be a separate entity from dermatofibroma, as it has an atypical morphology. The tumor consists of sheets of cells within the dermis and occasionally extends to the subcutis. Tumor cells have vesicular nuclei without significant atypia (Figure 15). Clear cell dermatofibroma histology overlaps with recently described clear cell mesenchymal neoplasm, characterized by a dermal proliferation of cells with vesicular nuclei and clear to lattice cytoplasm with or without cytological atypia and mitosis.

Deep fibrous histiocytoma

Deep fibrous histiocytoma resembles dermatofibroma histologically but affects the deep subcutis or soft tissues (figure 16). The extremities are the most frequent site followed by the head and neck and then the trunk. Up to one in five deep fibrous histiocytomas recur after excision, and there are 2 reported cases of metastasis and death.

Distinctive histologic features of deep fibrous histiocytoma include a diffuse stormy pattern and hemangiopericytoma-like changes with branching, thin-walled deer horn-shaped vessels at 40% of lesions. different to cutaneous dermatofibroma, these lesions are often positive for CD34.

Special dermatofibroma studies.

Immunohistochemical positive for Factor XIIIa.

CD34 is usually negative in dermatofibroma, but highlights intermingled vessels and can be focally positive at the periphery of the lesion in the cell variant (Figure 17). Factor 13A generally stains the lesion cells (Figure 18). There is variable positivity for CD68 and smooth muscle actin. An epithelioid fibrous histiocytoma is often ALK-1 positive.

Pale dermatofibroma

Pale dermatofibroma is characterized by a prominent palisade of nuclei, mimicking the bodies of Verocay seen in schwannoma. Differential features of schwannoma include the lack of a capsule, and staining for S100 is negative (S100 is positive in schwannoma) (Figures 19, 20, 21).

Atrophic dermatofibroma

Atrophic dermatofibroma likely represents the final stage of a dermatofibroma and often presents clinically as a depressed lesion. Histologically, tumor cells are sparsely distributed among abundant hyalinized collagen