ABSTRACT
BACKGROUND: Cutaneous metastases occur in 0.6-10.4% of all patients with underlying malignancy. Among them, the site of origin remains unknown in 4.4-14.5% of all cases. CASE: The authors describe a 68-year-old man with widespread skin and soft tissue metastases appearing as the first and dominant clinical manifestation of oncologic disease. Physical examination and CT scans revealed multiple cutaneous and subcutaneous tumor nodules arising in the neck, chest, abdomen, lumbar region and right forearm, as well as in the gluteal and iliacus muscles and in the proximal part of the left thigh. Light microscopy confirmed a metastasis of adenocarcinoma exhibiting a tubuloglandular pattern and a slight mucin production. It was immunoreactive for cytokeratin 7 and carcinoembryonic antigen and negative for cytokeratin 20, CDX-2, TTF-1 and prostatic specific antigen. Based upon the histomorphology and immunophenotype, the pathologist suggested a primary tumor in the stomach or biliopancreatic tract. However, further clinical workup did not clearly identify a primary lesion. CONCLUSION: Determining the origin of cutaneous metastases might be a challenging issue for both clinicians and pathologists. The case we describe is uncommon because widespread skin and subcutaneous metastases appeared as the first and dominant clinical sign of adenocarcinoma, the origin of which has not been established. This unusual tumor behavior may suggest that a spreading and colonization of metastatic cancer cells in the skin and soft tissue may be a specific biologic process.Key words: skin metastases - malignancy of unknown origin - adenocarcinoma.