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Histologic analysis of keloids and hypertrophic scars.

To the Editor: We would like to comment on the article entitled “Should Excised Keloid Scars Be Sent for Routine Histologic Analysis?” by Gulamhuseinwala et al. and the letter that was sent by Wong et al. in response to this article. Gulamhuseinwala et al. reported their pathologic analyses of 568 scars, of which 458 (81%) were classified as “keloids,” 60 (11%) as “acne keloidalis,” 35 (6%) as “hypertrophic scars (HSs),” and 14 (2%) as “normal scars.” There were no reported malignancies or dysplasias. It was concluded that it may be unnecessary to send a specimen at excision for routine histology if there is reasonably good clinical suspicion that it is a keloid. In response, Wong et al. suggested that since malignant or local destructive tumors such as giant cell fibroblastoma and dermatofibrosarcoma protuberans (DFSP) could be misdiagnosed as keloids clinically. Routine histologic analysis should be performed if a pathologic examination can offer less uncertainty and a higher probability of correct diagnosis at a relatively small cost. In relation to this, we would like to report our own experiences. We have an outpatient clinic in our facility that is solely devoted to scar management and have found that many of the patients with keloids or HSs had diagnosed themselves and visited us of their own accord. This suggests that physicians and other medical professionals may overlook similar diseases of keloid/HS in some cases. When we examined 378 patients who had diagnosed themselves with keloids/ HSs and were treated by us from April 2003 to March 2007, we found that the scars in 1.06% were actually tumors, namely, apocrine cystadenoma, adult-onset juvenile xanthogranuloma, mixed tumor, and chronic folliculitis (fortunately, all tumors were benign). In our experience, even knowledgeable physicians can misdiagnose scars as keloids/HSs clinically. This possibility is increased by the fact that both malignant tumors and keloids rapidly grow not only vertically but also horizontally. Thus, we recommend routine histologic analysis after surgical excision of keloids/HSs. We would also like to raise a number of matters that relate to this issue, as follows. First, the clinician should clearly understand why they are requesting histologic analysis of an excised scar, namely, is it to exclude the possibility of malignancy or is it to provide a differential diagnosis between keloids and HSs (or both)? Second, the clinician should adequately convey to the pathologist why a pathologic examination is being requested. Third, we recommend that scar biopsies should be taken in some cases for histologic analysis, and fourth, since some scars can be difficult to diagnose on the basis of existing clinical and histologic criteria that distinguish between keloids and HSs, histologic analyses of other features may be useful for resolving these cases. With reference to the third point, clinicians should also consider whether taking biopsies of the scar for histologic examination may be useful. In general, taking a biopsy of a keloid/HS is contraindicated because even a small wound inflicted by a surgical procedure may promote keloid/HS growth. However, we recommend that biopsies should be performed in anomalous cases or when the keloids/HSs become more severe. With regard to the differential diagnosis between keloids and HSs, clinicians should know that pathologists distinguish between keloids and HSs pathologically on the basis of the presence of the thick eosinophilic (hyalinizing) collagen bundles that characterize keloids but are lacking in HSs. In turn, pathologists should know that clinicians distinguish between keloids and HSs clinically on the basis of the presence of horizontal growth, which characterizes keloids and not HSs. However, while many traditional textbooks treat keloids and HSs as completely different types of scars, we have encountered cases in our clinic where the scar bore features of both keloids and HSs (Fig. 1). Thus, it may be difficult for a clinician to distinguish between keloids and HSs by just considering their horizontal growth pattern. Similarly, for histologists, the degree to which a scar bears hyalinizing fibers is graded and the presence of an intermediate grade can make it difficult for them to distinguish keloids from HSs (Fig. 2). We speculate that the diagnosis of these cases may be aided by identifying other clinical and histopathologic features that distinguish keloids from HSs. For example, both scar types bear chronic inflammation, the abnormal deposition of extracellular matrix components, and the presence of an excess of microvessels. In particular, both scar types contain significantly higher numbers of macrophages, lymphocytes, and mast cells and their subpopulation proportions than normal skin. These features are gradable and thus many intermediate stages may be available. Careful observation may show that these features differ in degree between keloids and HSs. This would not only be useful for diagnosing between keloids and HSs, it might also illuminate the different mechanisms by which keloids and HSs are generated. In relation to this point, I would like to recommend that Gulamhuseinwala et al. reconsider the histologic difference between keloids and HSs when designating their 568 specimens as keloids or HSs. While they recorded 458 specimens as being keloids, we speculate that these included various grades of keloids. In summary, we recommend that routine histologic analysis should be performed on surgically excised keloids/HSs but that clinicians should convey to the pathologists