Cutaneous Metastatic Lesions as a Rare Manifestation of Colorectal Adenocarcinoma: A Case Report.

Cutaneous metastasis is an uncommon manifestation of colorectal cancer, usually occurring in an advanced disease state. We present a case of a 93-year-old man with a history of multiple non-melanoma skin cancers who was previously diagnosed with primary adenocarcinoma of the colon. The patient presented with three nodules on his upper back that developed over a few weeks. Physical examination revealed two erythematous, firm, dome-shaped nodules without discharge, and a third, smaller, flesh-colored, and non-ulcerated lesion. No palpable regional lymphadenopathy was noted. Two punch biopsies were performed on representative lesions. Histopathologic analysis demonstrated irregular glandular structures infiltrating the dermis, composed of atypical mucin-producing columnar cells with abundant eosinophilic cytoplasm and extracellular mucin deposits interspersed among collagen fibers. Immunohistochemical staining was positive for CDX2, CK20, and SATB2, and negative for CK7, findings consistent with metastatic colorectal adenocarcinoma. The patient's clinical course was consistent with advanced disease, and he passed away approximately three months after the onset of cutaneous lesions. This case highlights the importance of recognizing cutaneous metastases as a potential indicator of systemic spread in patients with a history of colorectal cancer. Prompt dermatologic evaluation, histopathologic confirmation, and multidisciplinary coordination are crucial for accurate staging and effective care. Greater awareness and standardized guidelines are necessary to enhance the diagnostic approach and management of this rare yet clinically significant manifestation.