A Case of Invasive Extramammary Paget's Disease with Signet Ring Cells

Abstract

A 72-year-old Japanese man had a seven month history of ill-defined erythema at the left inguinal region. This erythema had gradually enlarged and formed indurated mass. A skin biopsy from the indurated mass revealed tumor cells with signet ring cells, mainly in dermis. We suspected metastatic adenocarcinoma at first, but no masses were detected elsewhere. A total resection was performed. Histological evaluation of the epidermis revealed typical Paget's cells. Prominent signet ring cells formed nests in the superficial dermis, and marked proliferation of small cells appeared as linear strands and solid masses. Immunohistochemical staining was positive for cytokeratin 7 (CK7), cytokeratin 20 (CK20), and gross cystic disease fluid protein-15 (GCDFP-15). He was finally diagnosed with primary invasive extramammary Paget's disease. Because signet ring cells emerge in secondary Paget's disease, metastatic skin tumors, and primary skin tumors, it is necessary to distinguish primary Paget's disease from the other possibilities. In this diagnostically difficult case, an accurate conclusion was achieved by comprehensive inspection results.