Clinicopathologic Features and Ki-67 Expression in LargeCell Acanthoma / 대한피부과학회지

ABSTRACT

BACKGROUND: 1970, Pinkus described large cell acanthoma(LCA) as a benign epidermal neoplasm which clinically resembles a actinic keratosis or seborrheic keratosis. However, the entity of this disease is still unclear.OBJECTIVE: The purpose of this study was to find out if LCA is a distinctive entity by investigating its clinical features, histopathologic features and Ki-67 expression. METHODS: 20 LCA samples including normal tissue were analyzed after investigating their clinicopathologic features and immunohistochemical analysis of Ki-67 expression which was performed on the formalin-fixed, praffin-embedded tissue section. The assessment of immunohistochemical staining was based on the growth fraction(GF), defined as the number of Ki-67 positive cells divided by the total number of tumor cells counted, and was expressed in a percentage. RESULTS: 1. LCA was usually presented as a well demarcated, brown or light brown, 5 to 30 mm, round, flat to hyperkeratotic scaly patch and plaque. It predominantly affected female (5.6 females1 males) aging from 37 to 76 years of age(mean 51 year-old). The duration of LCA ranged from 6 months to 30 years. In eleven cases, the lesion was located on the face and in nine cases, on the extremities. Eight cases showed a solitary lesion and twelve cases showed multiple lesions. Transformation to malignancy was not found.2. Histopathologic study showed sharply circumscribed epidermal neoplasms characterized by large (approximately twice the normal size) uniform keratinocytes with proportionally large nuclei and an increase of melanin in the basal layer. In many cases, hypergranulosis(18 cases) and hyperkeratosis(17 cases) were observed. Occasionally, acanthosis(10 cases), papillomatosis(9 cases) and epidermal atrophy(7 cases) were also observed. However, keratinocyte necrosis was not observed. Moderate solar elastosis and moderate lymphocytic infiltration was observed in the upper part of the dermis in all cases. Mild and moderate melanin incontinence was observed in 14 cases and 1 case respectively. Appendage involvement(follicular infundibulum and acrosyringium) was observed in all cases.3. The Ki-67 expression of LCA tissue(4.87 +/- 3.10%) was significantly higher than the adjacent normal skin(2.50 +/- 1.89%, p=0.01). CONCLUSION: Our study of the clinical and histopathologic features and the expression of Ki-67 strongly suggests that LCA is a distinctive entity.