Giant combined dermatofibroma

Sir, Giant dermatofibroma is a rare clinical variant. The correct diagnosis is usually not suspected because of its large size.1 We report a case of giant dermatofibroma, showing combined histological features of haemangiopericytoma‐like, epithelioid benign fibrous histiocytoma and probable myofibroblastic differentiation. A 47‐year‐old woman presented with a 12‐year history of a tumour on her back. It had been resected once, but recurred 2 years later, and had gradually increased in size. There was occasional bleeding, but no trauma was noticed. Neither past medical history nor family history was remarkable. Results of laboratory testing including serum cholesterol and triglycerides were normal. Examination of the back revealed a flesh‐coloured, elastic‐hard, pedunculated, round tumour with smooth and slightly keratotic surface, measuring 12 × 12 × 3 cm, on the lower back (Fig. 1a,b). The patient also demonstrated four pea‐sized brownish nodules on her trunk and right leg, which were clinically diagnosed as dermatofibromas. A biopsy specimen of the giant tumour revealed dermatofibroma. However, the possibility of malignancy was considered because of its huge size. Therefore, the tumour was excised with a 2‐cm wide and deep margin, including the fascia. During surgery, apparent feeding vessels were found in the pedicle of the tumour. There has been no evidence of recurrence after 25 months of follow‐up. The other four nodules were also excised, and histologically confirmed as simple dermatofibromas. The pedunculated tumour on her lower back. The surface is red or red‐black, smooth, and slightly keratotic. (a) Front view of the tumour; (b) side view. On microscopic examination, the giant tumour showed multinodular cellular proliferation with prominent ectatic vascularity involving the dermis to the subcutis. It was divided into an exophytic part and a pedicle. In the exophytic part, the tumour cells compactly occupied the papillary dermis down to the deep dermis without a storiform arrangement. Larger vessels with a muscle coat were found through the tumour. Haemorrhages and haemosiderin‐laden macrophages were found in the upper part of the tumour. The overlying epidermis showed hyperplasia or ulceration in some places. A clear zone was not obvious. In the pedicle, tumour cells were detected from the subcutis to the fascia without a honeycomb pattern. Characteristically, prominent ectatic vascularity presenting a crow's foot or chicken wire appearance was noticed through the tumour (Fig. 2). Most vessels were somewhat thick‐walled, ovoid capillaries with variably dilated lumina. The presence of epithelioid cells in close proximity to prominent capillaries imparted a haemangiopericytoma‐like appearance. However, unlike the arrangement in haemangiopericytoma, the vascular endothelium was separated from the epithelioid cells by a well‐defined rim of connective tissue. The pediculate parts of the tumour. The tumour cells are detected in the subcutis with prominent, ectatic vascularity. (Original magnification × 8). In most lesions, the tumour cells were tightly clustered. A large number of them were large epithelioid cells with abundant eosinophilic cytoplasm (Fig. 3a). Nuclei were eccentrically placed, with vesicular chromatin and small nucleoli. There was no nuclear atypia and no mitotic figures. Furthermore, intermingled with the epitheloid cells were a moderate number of xanthoma cells with a single or grouped arrangement. A greater number of foam cells were detected in the deeper lesion. At the peripheral leading edge of the lesion, the fascicular pattern of prominent spindle cells, probably myofibroblasts, was striking (Fig. 3b). The characteristics of epithelioid benign fibrous histiocytoma with xanthomatous expression in the centre of the tumour (a) and the fascicular pattern at the periphery of the tumour (b). (Original magnification a and b: × 66). Twenty to 30% of the tumour cells expressed weak‐to‐moderate reactivites for factor XIIIa in the peripheral lesion and for histiocytic markers such as CD68 and HLA‐DR especially in the deep lesion. However, they did not react with S‐100‐protein, CD34, CD31, α smooth muscle actin and desmin. Areas of prominent vascularity demonstrated positivity for CD34, CD31 and α smooth muscle actin. Xanthoma cells showed marked reactivity for CD68. Based on these findings, we made a diagnosis of a giant combined dermatofibroma showing combined features of haemangiopericytoma‐like, epithelioid benign fibrous histiocytoma with xanthomatous aggregates, and probable myofibroblastic differentiation. The features of giant dermatofibroma include: (1) diameter ≥ 5 cm; (2) a pedunculated appearance; (3) a benign behaviour despite the large size; and (4) the same histopathological characteristics as conventional dermatofibroma.1 Three new cases including ours have been reported2–3 and there have probably been about 15 cases. The peculiarities of our case included the deep penetration of the tumour cells and the combined histological features, differing from those of conventional dermatofibroma. Clinically, this case was the largest among the previous reported cases of giant dermatofibroma.1–3 Many histological variants of dermatofibroma have been described. Prominent ectatic vascularity has been reported in haemangiopericytoma‐like and epithelioid benign fibrous histiocytomas.4–6 It is well known that dermatofibroma has almost no propensity to recur. However, some variants show potential for local recurrence.6–7 The shared finding of recurrent variants is prominent vascularity, which was also found in our case. The increased vascularity and haemorrhage in the lesion, to a certain extent, could be related to possible trauma. However, this vascularity may play an important role in progression of this tumour to such a large size, similar to the vascular ectatic mechanism which has been shown in the pathogenesis of verruciform xanthoma.8