Skin metastasis: from conceptual to practical guidelines.

Of the outward manifestations of visceral malignancy, cutaneous metastases are of particular interest for their impact on identification, prognosis, and management of the primary tumor. Their diagnosis is often challenging and requires high clinical suspicion. The infrequency and clinicopathologic variability of cutaneous metastases can impede their recognition by physical exam and even histopathology. This review offers a practical approach to judicious utilization of the full repertoire of clinical and pathologic data in precise characterization of metastases to the skin. Highlighted are commonly encountered entities, with emphasis on clinical and pathologic differential diagnoses, and clues to identification. Special mention is made of metastases of unknown primary and the special position occupied by hematolymphoid malignancies directly manifesting in skin.