Annular skin tumors and lymphoproliferative diseases

Determining the shape of the skin lesion may provide a diagnostic clue in dermatology practice, more commonly for inflammatory diseases but also for skin tumors. The annular formation may develop by diverse mechanisms in skin tumors. Annular lesions may occur from the onset of the tumor as sparing the central area or depression and/or ulceration in the center of the tumor or outward expansion of the primary lesion. Clustering of multiple papulonodular lesions sparing the central area or relatively independent processes acting on the central and peripheral components of the tumor may also result in an annular appearance. We have explored a wide variety of benign and malignant skin tumors and lymphoproliferative diseases forming an annular shape.