A Clinicopathologic Study of Clear Cell Actinic Keratosis / 대한피부과학회지

ABSTRACT

BACKGROUND: Clear cells are defined as cells that contain abundant, clear, lightly eosinophilic cytoplasm. On rare occasions, clear cell changes have been observed in actinic keratosis (AK). OBJECTIVE: We aimed to evaluate the cytoplasmic contents of clear cells and the clinicohistopathological features of clear cell AK. METHODS: From 456 cases of histopathologically confirmed AK, we selected 30 cases (6.6%) with greater than 10% of clear cells in the epidermis. We collected the demographic data and clinical features for all specimens. In addition, the specimens were divided into five histopathologic types: hypertrophic, atrophic, Bowenoid, acantholytic, and pigmented. Clear cell distribution was classified into 3 categories: upper, middle, and lower areas of the epidermis. Periodic acid-Schiff (PAS), PAS diastase (d-PAS), and alcian blue staining were carried out, and immunoperoxidase stainings were performed for S-100, HMB45, and cardio embryonic antigen (CEA) to evaluate the origin of the clear cytoplasm. RESULTS: The cheek was the most common site of involvement. The most frequent lesion color was erythematous (66.7%). Scale and telangiectasia were found in the majority of patients (90% and 66.7%, respectively). The most common histopathological type was Bowenoid, found in 21 cases. This was followed by hypertrophic in 7 cases and pigmented in 2 cases. Seventeen specimens (56.7%) stained positive for PAS and negative for d-PAS. All of the PAS-positive specimens were Bowenoid AK. All specimens stained negative for alcian blue and immunoperoxidase staining results were negative for S-100, HMB 45 and CEA. CONCLUSION: We conclude that clear cells in AK most likely originate due to an accumulation of glycogen or due to hydropic degeneration. The presence of glycogen in clear cells may induce adnexal differentiation to an atypical keratinocyte in AK.