Chapter 48 Cutaneous metastases
1. How often do internal malignancies metastasize to the skin?
Cutaneous metastases of internal malignancies are relatively uncommon. An autopsy study including 7500 patients with internal malignancies demonstrated cutaneous metastases in 9% of patients. Most cases occur late in the course of the disease, but cutaneous metastasis may also be the initial presentation of an internal malignancy.
2. By what three routes do internal malignancies metastasize to the skin?
They extend by local infiltration, lymphatic spread, or hematogenous spread. Breast carcinoma and oral cancer are the most likely to demonstrate direct extension into the skin. It is assumed that the fundamental mechanisms are similar to those of metastasis to parenchymal organs, but this has not been investigated. Rare cases have been inoculated by local procedures such as needle biopsies.
3. How do malignant cells invade and metastasize?
The genetic and molecular events that allow cells to invade and metastasize are a complex issue that is being studied in numerous laboratories. Malignant cells must be able to detach from adjacent cells (i.e., downregulate adhesion molecules), adhere to the adjacent matrix by the development of receptors to matrix molecules, such as fibronectin; lyse the extracellular matrix by the production of various enzymes; and migrate by the production of motility factors, such as hepatocyte growth factor. Once the tumor cells gain access to lymphatic spaces or blood vessels, they must be able to express adhesion molecules on their surface, which then allows them to attach to endothelial cells (e.g., CD44). There is also evidence that certain normal tissues produce chemoattractants that may attract tumor to a specific site.
Nguyen TH: Mechanisms of metastasis, Clin Dermatol 22:209–216, 2004.
4. What are the most common cancers that metastasize to the skin in women?
Different gender and age groups are affected by somewhat different metastatic malignancies. In a large study done at the Armed Forces Institute of Pathology in the early 1970s, the most common etiologies of cutaneous metastases in women were:
