Expression of Proton-Sensitive GPR31, GPR151, TASK1 and TASK3 in Common Skin Tumors

TWIK-related acid-sensitive potassium channels TASK1 and TASK3, as well as the G-protein-coupled receptors GPR31 and GPR151, are proton-sensitive membrane proteins. They can be activated or inhibited by low extracellular pH (pHe), which is a hallmark of the tumor microenvironment in solid tumors. However, the role of these channels in the development of skin tumors is still unclear. In this study, we investigated the expression profiles of TASK1, TASK3, GPR31 and GPR151 in squamous cell carcinomas (SCCs), basal cell carcinomas (BCCs), nevus cell nevi (NCN), and malignant melanomas (MMs). We performed immunohistochemistry using paraffin-embedded tissue samples from patients and found that most skin tumors express TASK1/3 and GPR31/151. The results show that BCCs are often negative for GPR31/151 as well as for TASK1/3, while nearly all SCCs express these markers. MMs and NCN show similar expression patterns. However, some tumors show a decreasing TASK1/3 expression in deeper dermal tumor tissue, while GPCRs were expressed more evenly. The lower frequency of GPR31/151 and TSAK1/3 expression in BCCs when compared to SCCs is a novel histological feature distinguishing these two entities. Moreover, BCCs also show lower expression of GPR31/151 and TASK1/3 as compared to NCN and MMs.

Case of a Giant Conjunctival Melanocytic Nevus

A 78-year-old female experienced extraocular extension of a giant conjunctival melanocytic mass. The clinical diagnosis was conjunctival malignant melanoma. We performed local excision and histopathological examination. The result of hematoxylin-eosin staining disclosed multiple intralesional mucosal cysts and nevus cell nests with abundant melanin. Immunohistochemical examination revealed expression of S-100, melan-A, and HMB-45 and no expression of Ki-67. Histopathological examination showed no evidence of malignancy. Giant conjunctival melanocytic nevi can be diagnostically confused with conjunctival malignant melanoma.

Benign Cutaneous Tumors

Tumors of the cutaneous surface may arise from the epidermis, dermis, or subcutaneous tissue or from any of the specialized cell types in the skin or its appendages. Broad categories include tumors derived from epithelial, melanocytic, or connective tissue structures. Within each location or cell type, lesions are classified as benign, malignant, or, in certain cases, premalignant. Benign epithelial tumors include tumors of the surface epidermis that form keratin, tumors of the epidermal appendages, and cysts of the skin. Melanocytic (pigment-forming) lesions are very common. One of the most frequently encountered forms is the nevus cell nevus. Tumors that are derived from connective tissue include fibromas, histiocytomas, lipomas, leiomyomas, and hemangiomas. This chapter provides an overview of each type of tumor, including sections on epithelial tumors, tumors of the epidermal appendages, familial tumor syndromes, melanocytic tumors, neural tumors, connective tissue tumors, vascular birthmarks, acquired vascular disorders, Kimura disease, lipoma, leiomyoma, and lymphangioma circumscriptum. The sections discuss various forms and their diagnosis, differential diagnosis, and treatment. Figures accompany the descriptions. This chapter contains 83 references, 26 highly rendered figures, and 5 MCQs.

Benign Cutaneous Tumors

Tumors of the cutaneous surface may arise from the epidermis, dermis, or subcutaneous tissue or from any of the specialized cell types in the skin or its appendages. Broad categories include tumors derived from epithelial, melanocytic, or connective tissue structures. Within each location or cell type, lesions are classified as benign, malignant, or, in certain cases, premalignant. Benign epithelial tumors include tumors of the surface epidermis that form keratin, tumors of the epidermal appendages, and cysts of the skin. Melanocytic (pigment-forming) lesions are very common. One of the most frequently encountered forms is the nevus cell nevus. Tumors that are derived from connective tissue include fibromas, histiocytomas, lipomas, leiomyomas, and hemangiomas. This chapter provides an overview of each type of tumor, including sections on epithelial tumors, tumors of the epidermal appendages, familial tumor syndromes, melanocytic tumors, neural tumors, connective tissue tumors, vascular birthmarks, acquired vascular disorders, Kimura disease, lipoma, leiomyoma, and lymphangioma circumscriptum. The sections discuss various forms and their diagnosis, differential diagnosis, and treatment. Figures accompany the descriptions. This chapter contains 83 references, 26 highly rendered figures, and 5 MCQs.