RESUMEN
BACKGROUND: Dermatofibroma is a common benign fibrohistiocytic lesion that occurs most commonly on the legs of middle-aged women. OBJECTIVE: The study was performed to evaluate the clinical, histopathological and immunohistochemical features of dermatofibromas according to the duration. METHODS: Sixty seven cases of dermatofibromas were selected from 12 years of laboratory files for the period January 1986 to June 1998 from two medical hospitals. RESULTS: 1. The age range was from 10 to 69 and the average age at diagnosis was 36.0 (male;38.3, female;34.5). The ratio of male to female was 1.0:1.5 (27:40). 2. Fifty eight cases(86.5%) had solitary lesions, and nine cases(13.5%) had multiple lesions. 3. The lower extremities(40 cases, 50.6%) were the most common sites followed by the upper extremities(16 cases, 20.9%), abdomen(5 cases, 6.3%), shoulders(4 cases, 5.0%), back(3 cases, 3.7%), hands(3 cases, 3.7%), neck(2 cases, 2.5%), buttock(2 cases, 2.5%), breast(1 cases, 1.2%), face(1 cases, 1.2%), axilla(1 cases, 1.2%) and foot(1 cases, 1.2%). 4. The most common color was brown (50 cases, 74.7%), and other common colors were red(10 cases, 14.9%), black (4 cases, 5.9%), violaceous (3 cases, 4.5%). 5. Histopathologically, fibrous types were seen in 51 cases(76.1%), cellular types in 6 cases (8.9%), mixed types in 7 cases(10.4%), and sclerosing hemangiomas in 3 cases(4.6%). 6. All lesions were positive for factor XIIIa. However, the degree of staining was different according to the duration; less than 1 year(10 cases-strong positive), between 1 to 5 years (3 cases-strong positive, 7 cases-moderate positive), more than 5 years(2 cases-moderate positive, 3 cases-weak positive). 7. Results of Masson's trichrome and Verhoeff-van Gieson stain showed that normal appearanced collagen and elastic fibers were increased in the lesion according to the duration and mucin depositions were also more increased in the old lesion than the younger lesion by alcian blue stain. CONCLUSION: On the basis of our result, we believe that factor XIIIa-positive cells seen in dermatofibroma represent reactive stromal cells rather than true tumor cells. Further studies are needed to determine whether the other factors are related to the pathogenesis of dermatofibroma.