Cutaneous metastases are rare. Their incidence report ranges from 0,7 to 10,5% in autoptic and retrospective studies [4
]. In order of decreasing frequency, the sources are breast and lung cancer, melanoma, and squamous carcinoma of the upper tract. Among gastrointestinal malignancies, gastric cancer is the most common neoplasm to present with skin involvement [2
]. Cutaneous metastases from large bowel carcinoma account for approximately 5% of all skin secondaries [1
]. Liver, peritoneal, and lung involvement is generally associated [3
]. The gross appearance of lesions is not distinctive, and biopsy is often needed for the diagnosis. Usually they appear as painless nodules within the dermis and subcutaneous tissue, with intact and uninvolved epidermis, within the first two years after resection of the primary tumor [1
]. Cutaneous metastases may be the first clinical sign of relapse or, more rarely, may reveal an asymptomatic malignancy [4
]. Anyway, they generally represent a poor prognostic sign. Several explanations for their development have been proposed. Direct extension through lymphatic or surgical tracts seems to be an important mechanism since most of lesions are located in the skin overlying the abdominal wall, in a colostomy site or in the surgical incision [1
]. Metastases at the trocar site or at the minilaparotomy incision have been reported after laparoscopic-assisted colectomy [10
]. Implantation during surgery may contribute to this type of recurrence. Other possible routes of dissemination are extensions along ligaments of common embryonic origin, such as the round ligament of the liver. Metastasis to the umbilicus from an internal malignancy is well known as the “Sister Mary Joseph's nodule” [11
]. Distant metastases, in order of decreasing frequency, have been seen in pelvis, upper extremities, chest, and back skin. There are rare reports of metastases of the head, neck, tongue, lip, and hands [4
]. Remote lesions are usually associated with organ involvement and are believed to be due to diffuse hematogenous dissemination of tumor cells and to their trapping in the capillary bed of the skin, just for mechanical factors.
The case we report is unusual because remote cutaneous metastases are not associated with visceral secondaries. It seems unlikely that the tumor cells locate throughout the skin just for mechanical factors without hepatic or pulmonary involvement, since lung and liver receive all of the venous drainage from the colon, prior to distribution to the rest of the body. It seems reasonable to suppose that circulating tumor cells bind specifically to the skin by site-specific adhesion molecules and/or respond preferentially to growth factors found at that site.