A 48 year old woman presented with a long standing skin lesion on the calf, which had been progressively increasing in size and was painful. After excision, histology showed a spindle cell and histiocytic lesion with a storiform pattern containing foamy histiocytes admixed with large numbers of dilated blood vessels. The lesion was reported as a cellular dermatofibroma with prominent vasculature.
Take home messages
- We describe a case of aneurysmal fibrous histiocytoma (AFH), which was aggressive and recurrent
- It is important to distinguish this benign lesion from similar appearing malignant skin lesions
- Squamous lined cysts were present within this tumour, a finding that has not been described previously
However, the lesion recurred twice at the same site and the final excision was performed down to the fascia. The lesion measured 2.5 cm and contained a well defined cystic tumour. Microscopic examination showed a resemblance to the original lesion, although it now contained cystic, blood filled spaces, the larger of which were lined by squamous epithelium. The smaller cysts had no lining, but were bordered by intervening spindle shaped cells extending to the subcutaneous tissue (figs 1 and 2).
Fibrohistiocytic cellular proliferation containing numerous blood filled cysts, the largest measuring 8 mm. Stromal haemosiderin deposition was confirmed by Perls staining. Haematoxylin and eosin stain; original magnification, ×100.
Figure 2 The cysts lacked an endothelial lining and were bordered by epithelioid and spindle shaped cells with eosinophilic cytoplasm showing a storiform pattern. Pleomorphism was mild and occasional mitoses were present. Haematoxylin and eosin stain; (more ...)
Immunohistochemistry for CD34 confirmed the absence of an endothelial lining around the small blood filled spaces and cytokeratin staining confirmed the presence of squamous epithelium around the larger cysts (figs 3 and 4).
The larger cysts were bordered by a squamous lining beneath which were fibrohistiocytic cells. Haematoxylin and eosin stain; original magnification, ×200.
The squamous lining lacked a granular layer and its epithelial nature was confirmed by cytokeratin (AE1/AE3) immunoreactivity. Haematoxylin and eosin stain; original magnification, ×400.
The features were consistent with the rare aneurysmal variant of fibrous histiocytoma. The patient required skin grafting one month after the third excision.