Aneurysmal Dermatofibroma: Uncommon Presentation of Common Disease

one of the uncommon histological variants of dermatofibroma, which closely mimics vascular lesions. It is usually larger than typical dermatofibroma and may show rapid growth. 4 Here we report a rare and interesting case of aneurysmal dermatofibroma which resembled verrucous hemangioma clinically but


Introduction
Dermatofibroma (DF), /benign fibrous histiocytoma, is a commonly occurring cutaneous entity usually centered within the dermis.It is a benign dermal and superficial subcutaneous myofibroblastic proliferation, microscopically mimicking fibromatosis.Dermatofibroma is generally reported on the trunk or extremities in adults between 20 and 49 years old, with women being more frequently affected than men. 1 Based on specific histopathological features, many variants of dermatofibroma have been identified in the literature which include cellular DF, aneurysmal DF, atypical DF, epithelioid DF, atrophic DF, ulcerated DF, erosive DF, and lichenoid DF. 2 Clinically, they present as dome shaped, firm papules or nodules that usually range from a few millimeters to occasionally up to 2 cm in size. 3It may show a dimple sign that indicates tethering of the overlying epidermis to the underlying lesion. 2 Aneurysmal dermatofibroma is one of the uncommon histological variants of dermatofibroma, which closely mimics vascular lesions.It is usually larger than typical dermatofibroma and may show rapid growth. 4Here we report a rare and interesting case of aneurysmal dermatofibroma which resembled verrucous hemangioma clinically but  Based on clinical evaluation, provisional diagnoses of verrucous hemangioma, nodular basal cell carcinoma, and aneurysmal dermatofibroma were kept, and the patient was evaluated further.Ultrasonography of the lesion showed an approximately 9 x 5mm sized, well defined hypoechoic lesion noted in the subcutaneous plane with evidence of internal vascularity (possibility of slow flow venous malformation or melanocytic nevus).The lesion was then completely excised and sent for histopathological examination.H&E stained section of a skin biopsy revealed hyperplastic squamous epithelium with an underlying dermal lesion composed of short spindle and ovoid cells with irregularly shaped nuclei arranged in a storiform pattern along with vascular proliferation (Figure 3,4).Based on the clinical presentation and characteristic histopathological findings, the lesion was finally diagnosed as an aneurysmal dermatofibroma.

Figure-3:
10x magnification of a haematoxylin and eosin stained section of skin biopsy revealed hyperplastic squamous epithelium with an underlying dermal lesion composed of short spindle and ovoid cells with irregularly shaped nuclei arranged in a storiform pattern along with vascular proliferation.

Discussion
Aneurysmal dermatofibroma is considered to be a rare variant of dermatofibroma.It was first described by Santa Cruz and Kyriakos in 1981.4Clinically, aneurysmal dermatofibromas are characterized by benign, slowgrowing, smooth nodular lesions that are cystic in consistency and may be associated with pain.They vary in color, ranging from black, blue, and dark red in the early stages to brown and yellow in the later stages.The color is because of extravasation of erythrocytes and the presence of hemosiderin, and variations in color are likely due to various expressions of red blood cell degradation.1AneurysmalDF is reportedly associated with a vascular tumor-like pattern or melanoma-like pattern on dermoscopy.5 Histopathologically, aneurysmal DF shows large blood filled spaces bound by densely aggregated siderophages, but without the typical endothelial lining of vascular structures.Extravasation of red blood cells is seen along with sheets of large histiocytes and siderophages which are interspersed with small capillaries without endothelial atypia. 3ased on histological findings, features of aneurysmal DF can be confused with vascular or malignant tumors; hence, expert evaluation is necessary in view of the rarity of the occurrence of this disease.Additional investigations that help in differentiation include special stains like Prussian blue and immunohistochemistry (IHC).Siderophages in aneurysmal DF are Prussian blue positive, and IHC is positive for vimentin and negative for factors CD31, CD34, desmin, CD8, and XIIIa. 4In our case, the lesion closely mimicked verrucous hemangioma and pigmented nodular basal cell carcinoma on clinical examination as well as dermatoscopy.but histopathology showed characteristic findings that suggested aneurysmal dermatofibroma.Due to resource constraints, we could not do IHC or special stains.

Conclusion
Aneurysmal dermatofibroma is difficult to diagnose when it presents with atypical morphological features.
So this case report re-emphasizes the need for complete excision followed by a histopathological examination in all nodular lesions where the list for differential diagnosis is long and clinical as well as dermoscopic features are overlapping.

Figure- 1 :
Figure-1: single ,1*1 cm size well defined, non tender, erythematous nodule, having a violaceous hue with central reddish brown crusting and irregular puckered margins present over the left side of the upper back.

Figure- 2 :
Figure-2:On dermatoscopy (10x) = central bluish homogenous area with overlying whitish structures and a peripheral delicate pigment network along with vascular structure Based on clinical evaluation, provisional diagnoses of verrucous hemangioma, nodular basal cell carcinoma, and aneurysmal dermatofibroma were kept, and the patient was evaluated further.Ultrasonography of the lesion showed an approximately 9 x 5mm sized, well defined hypoechoic lesion noted in the subcutaneous plane with evidence of internal vascularity (possibility of slow flow venous malformation or melanocytic nevus).The lesion was then completely excised and sent for histopathological examination.H&E stained section of a skin biopsy revealed hyperplastic squamous epithelium with an underlying dermal lesion composed of short spindle and ovoid cells with irregularly shaped nuclei arranged in a storiform pattern along with vascular proliferation (Figure3,4).Based on the clinical presentation and characteristic histopathological findings, the lesion was finally diagnosed as an aneurysmal dermatofibroma.