SINGLE METASTATIC LESION
Occasionally, a single metastatic lesion containing adenocarcinoma or poorly differentiated carcinoma is identified, and a complete evaluation reveals no other evidence of disease. Such presentations can include a single lymph node or subcutaneous site or single lesions in various visceral sites, including bone, liver, lung, brain, and adrenal gland. The possibility of an unusual primary site mimicking a metastatic lesion should be considered (e.g., a subcutaneous nodule from a primary apocrine or sebaceous carcinoma rather than a metastasis), but this possibility can usually be excluded on the basis of clinical or pathologic features. PET is useful in excluding other metastatic lesions.
For patients with only a single identifiable lesion, definitive local therapy is recommended, guided by the site of tumour involvement. Such therapy may include surgical resection, radiation therapy, or a combination of these modalities. Although most of these patients eventually develop other metastatic sites, a significant disease-free interval is often experienced, and local treatment provides substantial palliation. The role of systemic chemotherapy in addition to definitive local therapy is not well defined; younger patients with poorly differentiated carcinoma or poorly differentiated adenocarcinoma are often treated with a short course of a taxane/platinum–based regimen.