A clinicopathologic study of the collagen types of connective tissue nevus

Background: The collagen type of connective tissue nevus is a hamartoma in which the amount of collagen is increased. It is divided into two groups: the inherited form that contains familial cutaneous collagenoma and shagreen patches in tuberous sclerosis, and the acquired form that contains eruptive collagenoma and isolated collagenoma. Objective: The purpose of this study is to investigate the clinical and histopathological features of the collagen type of connective tissue nevus, along with considering the associated systemic or genetic disorders. Methods: We retrospectively reviewed the medical records and biopsy specimens of 17 patients. Results: We compiled the clinical data and histopathologic feature of 17 patients with the collagen type of connective tissue nevus. The ratio of males to females was 1:1.125 and the mean age of onset was 12.2 years for the patients with eruptive collagenoma and 43.7 years for the patients with isolated collagenoma. Eruptive collagenoma was disseminated on the trunk and arms, but 1 case of eruptive collagenoma was localized on the left thigh. Isolated collagenoma developed as a solitarily lesion on the various sites. The lesions of eruptive collagenoma were less than 1 cm, but the size of the isolated collgenoma varied from 0.5 to 4 cm. Three cases of eruptive collagenoma presented with white-color lesions, but the rest of the eruptive collagenoma and isolated collagenoma showed flesh-colored lesions. No case was combined with congenital or systemic disease. Histopathologically, there were increased thickened collagen bundles that were randomly arranged in the dermis. The elastic fibers were decreased and fragmented. Conclusion: The collagen type of connective tissue nevus is benign and rare, and its clinical and histopathologic characteristics are similar with those of other dermal tumors or reactive disorders. Exact knowledge about the collagen type of connective tissue nevus is needed to differentiate connective tissue nevus from several other disorders that have similar characters and to disclose the association with other diseases.