The cutaneous histopathology of chemotherapeutic reactions.

The histological diagnosis of chemotherapy-induced cutaneous reactions is a difficult problem for the dermatopathologist. The initial effort should be directed towards obtaining as much clinical history as possible since the provided information is often incomplete and clinical correlation is usually required. The biopsy should be examined in a systematic fashion to assess the presence of damage to specific cutaneous structures. A recommended approach is to initially examine the epidermis and then proceed to hair follicles, eccrine sweat glands, vessels and dermis. The degree and pattern of damage will usually indicate whether or not a cytotoxic reaction is present. The intensity, pattern, and components of the inflammatory response should be assessed since they provide clues to whether a hypersensitivity reaction or immunomodulating chemotherapeutic reaction is present. In addition to the possibility of a chemotherapeutic reaction, the dermatopathologist must also consider the possibility of an infection since the host is usually immunocompromised and must also exclude the presence of a residual malignancy. After examination of the biopsy specimen and determination of the pathologic process or precesses, the observed findings should be correlated with the clinical history before rendering an interpretation.