Metastatic cancer to the skin is characterized by solitary or multiple dermal or subcutaneous nodules, occurring as metastatic cells from a distant noncontiguous primary malignant neoplasm, that are transported to and deposited in the skin or subcutaneous tissue by hematogenous or lymphatic routes or across the peritoneal cavity.
Includes detachment of cancer cells from primary tumor, invasion, intravasation into blood or lymphatic vessel, circulation, stasis within vessel, extravasation, invasion into tissue, proliferation at metastatic site. The growth of metastases depends on proliferation of metastatic cells, cytokine and growth factor release from cancer and stromal cells, angiogenesis, and immune reactions. Three patterns of metastases are observed: mechanical tumor stasis (anatomic proximity and lymphatic draining), site-specific (selective attachment of tumor cells to specific organ), nonselective (independent of mechanical or organ-specific factors).
Most cutaneous metastases occur in a body region near the primary tumor. The most common presentation of cutaneous metastases is nodules. The nodules are often nonpainful, round or oval, firm, mobile, and rubbery in texture. The nodules are usually flesh colored, although they may also be other colors (eg, from flesh colored to brown or blue-black).
Metastases of melanoma may simulate blue nevi and may be epidermotropic or simulate primary cutaneous melanoma.
Cutaneous metastases from squamous cell carcinoma in the oral cavity usually remain in the local area, most often affecting the neck and the face.
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