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Excerpt
We would like to thank Dr. Rose for his interest in our article on epidermotropic xanthoma (1) and for raising important points of discussion.
We do not believe fibrous papule with clear fibrocytes can be diagnosed instead of xanthoma based on the difference between vacuolated cells and foam cells. The difference between these two cell types is a very subjective and poorly defined difference related to the size of cells, the size of vacuoles, and the effects of tissue processing. Furthermore, the paper by Soyer et al. (2) describes the constituent cells of clear cell fibrous papule as often binucleate or multinucleate. In our report of epidermotropic xanthoma, all cells were mononucleate (Fig. 2 and 3). More importantly, clear cell fibrous papules were characterized by cells scattered through a stroma with coarse collagen bundles, which is a defining feature of common fibrous papules. In contrast, epidermotropic xanthoma consisted of sheets of vacuolated cells without intervening collagenous stroma. The intense staining of our lesion for CD68 (Fig. 4) in all tumor cells confirms the histogenesis as histiocytic and distinguishes it from clear cell fibrous papules, which exhibited only weak positivity. To our knowledge, strong CD68 staining has not been described with fibrous papules. Although it would be useful to perform Factor XIIIa staining on our lesion, no tissue remains in the paraffin block for such studies. Fibrous papules are typically Factor XIIIa positive dermal dendritic cell proliferations (3,4,5). Because fibrous papule with clear fibrocytes exhibited only weak Factor XIIIa positivity (2), the histogenesis of this neoplasm appears controversial. Based on the available data, we would reaffirm our diagnosis of epidermotropic xanthoma.
From a clinical perspective, two issues appear most significant. First, proper interpretation of these lesions as benign clear cell proliferations is important. Distinguishing epidermotropic xanthoma from malignant melanoma is particularly important in proper interpretation. Second, it is prudent to evaluate for hyperlipidemia in patients with xanthomas, while the risk of abnormal lipoprotein metabolism in patients with clear cell fibrous papules has not been determined to our knowledge.
