PAGETOID SQUAMOUS CELL CARCINOMA IN SITU/PAGETOID BOWEN DISEASE: A RARE CASE

Abstract

<h3>Background</h3> Pagetoid squamous cell carcinoma in situ/pagetoid Bowen disease (PSCCIS/PBD), a rare histologic variant of squamous cell carcinoma in situ/Bowen disease, is a tumor characterized by large pale morphology of atypical cells that is morphologically similar to the cells seen in Paget disease. <h3>Case</h3> A 66-year-old male patient underwent punch biopsy owing to a 1.1 × 0.3 cm ulcerovegetative lesion on his left auricle. The case was evaluated as compatible with PSCCIS/PBD. Total excision of the lesion was recommended. In microscopic examination of the total excision material, infiltration consisting of cells with large pleomorphic nuclei, prominent nucleoli, and clear cytoplasm that formed a nest pattern in some areas in the epidermis was remarkable. In the dermis, smooth limited epithelial invaginations with preserved basal membranes containing neoplastic cells and lesion involvement in the hair follicles were observed. There was no invasion. Mitosis was present in the lesion. Immunohistochemical analysis revealed diffuse nuclear staining with P40 and membranous staining with EMA and CK7 in tumor cells. CK5/6 showed positive staining in the basal layer in circumference of the lesion. HMB45 showed positive staining in dendritic melanocytes within the lesion. Based on histomorphologic and immunohistochemical findings, the case was evaluated as compatible with PSCCIS/PBD. <h3>Conclusions</h3> It is important to distinguish PSCCIS/PBD from extramammarian Paget disease and malignant melanoma in situ. Histopathologically and clinically, these lesions can be difficult to differentiate. Immunohistochemical study may be helpful in differential diagnosis.