INTRODUCTION

Squamous cell carcinoma of the skin is the second most common human cancer, occurring 300,000 times each year in the United States. SCC may behave aggressively and may metastasize to local lymph nodes or distant organs. The concept of in transit metastasis has been well described in melanoma but only recently described for primary cutaneous SCC. In-transit metastases from primary cutaneous SCC are more common in transplant recipients and signify poor prognosis in this group. In-transit metastases from cutaneous SCC in transplant recipients were described by Berg and Otley in 2002. Martinez, et al, expanded on this definition in an effort to describe the course of metastatic skin cancer in organ transplant recipients. In-transit metastases from primary cutaneous SCC are best described as subcutaneous or dermal relapse discontiguous from the site of the primary or locally recurrent tumor that occurs between the original site and the local nodal basin. Key defining features of in-transit metastases include the following: (1) in-transit metastases are distinct from local recurrence; (2) in-transit metastases are associated with factors indicative of high-risk SCC including large size, recurrence, and location on the forehead and scalp; (3) in-transit metastases are associated with long-term immunosuppression following organ transplant; and (4) in-transit metastases are associated with increased morbidity and mortality in organ transplant recipients.

PATHOGENESIS

Cancer can spread via direct extension, hematogenously, or through lymphatics. Local marginal recurrence is most often secondary to inadequate resection of tumor.