The clinical and histopathological study of Ota's nevus

Abstract

Background: Ota's nevus, characterized by the presence of melanocytes in the dermis, has been familiar among dermatologists, but the etiology, the pathophysiology, the clinical and histological classification are not entirely clear. To understand and elucidate them, more clinical studies and researches are necessary. Object: The aim of this study was to document the clinical and histopathological features of Ota's nevus. Methods: We examined 299 patients with Ota's nevus who visited the dermatology clinic in Korea from February 1993 to August 2003. Among them, 188 patients were biopsied. All the specimens were stained with hematoxylin and eosin. We examined the age & sex distribution, age of onset, seasonal variation, associated skin diseases, aggravating factors and color. We clinically classified Ota's nevus into 4 types according to Tanino's classification and histologically into 5 types based on the pattern of pigmentation. Results: 1. The ratio of male and female was 1:3. 2. The peak age of onset was at birth (28.4%) and puberty (24.8%). 3. Seasonal variation was observed with distinct aggravation in the summer (60%). 4. The associated diseases were 9 cases of persistent mongolian spot, 6 cases of nevus flameus, 4 cases of blue nevus, 3 cases of vitiligo, 3 cases of nevus of Ito, 2 cases of atopic dermatitis, 2 cases of psoriasis, 2 cases of cafe au late macules and 2 cases of contact dermatitis. 5. The aggravating factors were sunlight (35.8%), emotional stress (21.0%), menstruation (12.6%), cold exposure (9.5%), pregnancy (9.5%), fatigue (9.5%) and chemical agents (2.1%). 6. The color of lesions were blue black (36.8%), brown (34.8%), dark brown (16.1%) and slate (11.0%). 7. All cases were classified according to Tanino's methods: type Ia (23.1%), type Ib (20.1%), type II (26.7%), type III (9.4%), type IV (20.7%). 8. The histological subtypes of Ota's nevus were classified as: the superficial type (35.6%); the middermis type (5.9%), the superficial-middermis type (18.6%); the mid-lower dermis type (2.7%); the diffuse type was composed of the superficial dominant type (19.7%), the middermis dominant type (4.8%), the dispersed (true diffuse) type (12.2%) and the deep dominant type (0.5%). 9. In the relation between histological types and the color of the lesion: the superficial type had 31 cases of brown color, 15 cases of blue black color, 11 cases of dark brown color and 9 cases of slate color; the middermis type had 6 cases of blue black color and 2 cases of dark brown color, query number of cases of slate color; the superficial-middermis type had 12 cases of blue black color, 10 cases of dark brown color, 7 cases of brown color and 6 cases of slate color: the mid-lower dermis type had 3 cases of blue black color; for the diffuse type, the superficial dominant type had 13 cases of brown color, query number of cases of blue black color and 7 cases of dark brown color; the mid-dermis dominant type had 4 cases of brown color, query number of cases of dark brown color, the dispersed type had 14 cases of blue black color and 5 cases of brown color; the deep dominant type had 1 case of blue black color. Conclusion: The histological reclassification of Ota's nevus may be very useful in making a therapeutic prognosis of the disease.