Case report: a rare case of cutaneous lymphangitic carcinomatosis from colonic signet ring cell carcinoma.

Introduction and importance: Cutaneous metastasis from internal malignancies is rare, and cutaneous lymphangitic carcinomatosis (CLC) represents an even rarer subset characterized by tumor cell infiltration into the dermal and subcutaneous lymphatics. In this case report, we describe an unusual presentation of CLC originating from colonic signet ring cell carcinoma and highlight the importance of maintaining a high index of suspicion for timely diagnosis. Case presentation: A 24-year-old male patient with no prior history of malignancy presented to us with a 10-month history of progressive, painless bilateral lower limb and scrotal swelling accompanied by significant weight loss. Skin biopsy with immunohistochemical analysis confirmed cutaneous lymphangitic carcinomatosis secondary to metastatic colonic signet ring cell carcinoma. Clinical discussion: The incidence of cutaneous metastases is around 5.3-10.4% and only 4% of all cutaneous metastatic disease originates from colorectal cancers. Cutaneous lymphangitis carcinomatosis is an exceedingly rare presentation occurring in less than 5% of cases. The prognosis for patients with cutaneous lymphangitis carcinomatosis and cutaneous metastases in general is poor, with demise typically occurring within months after diagnosis of skin involvement. A high index of suspicion is required to correctly diagnose cutaneous lymphangitis carcinomatosis. Skin biopsy and immunohistochemical staining are essential for the diagnosis of cutaneous metastasis and determining the primary cancer. Conclusion: Given its infrequency and diagnostic challenges, this case underscores the importance of recognizing suspicious skin lesions as possible harbingers of undiagnosed visceral malignancy in patients with or without a history of cancer.