Atypical fibroxanthoma of the auricle.

occasionally xanthomized, with marked nuclear pleomorphism, prominent nucleoli and atypical mitoses (Fig. 2), together with multinucleated giant cells. Immunohistochemistry revealed positivity for vimentin (Fig. 3A), actin, CD68, CD99 and CD10, while results for S100, HMB45, CD34, desmin, caldesmon and cytokeratins AE1/AE3 and 20 (Fig. 3B) were negative, confirming that it was an atypical fibroxanthoma. This entity constitutes a diagnosis by exclusion, given that the image of fusocellular proliferation described is shared by other, more aggressive tumours such as desmoplastic melanoma, sarcomatoid squamous cell carcinoma and other pleomorphic sarcomas. Rarely producing metastasis, it is classified as a sarcoma of intermediate level of malignancy within the