Benign Cutaneous Lymphoid Infiltrates

The skin represents one of the organs in which the vast majority of diseases are associated with some manner of cutaneous lymphoid infiltration, or infiltration by other inflammatory cells. Just as benign processes can result in inflammatory disorders, so also atypical and malignant infiltrates of the skin can present a variety of different clinical manifestations. In addition to the classic inflammatory diseases of the skin such as psoriasis, seborrheic dermatitis, lichen planus, among others there is a definite group of diseases in which the presence of lymphocytic infiltrates occur with minimal epidermal involvement. These have been listed as the benign cutaneous lymphocytic infiltrates. They can be perivascular, nodular or diffuse in their presentation and some of them are so uniformly characteristic as they present that they are designated by specific names that allow not only for their diagnosis but often even for their causation. We will refer to a group of disorders, first which have classic names and very distinctive patterns of infiltration and then will discuss some of the more diffuse infiltrative lesions such as the so-called pseudolymphoma cutis or lymphocytoma cutis. For the sake of understanding and convenience of both clinical and pathologic manifestations, we will begin with a discussion of the superficial and then the superficial and deep cutaneous disorders and then the diffuse infiltrative lesions.