Cutaneous Metastasis From Rectal Adenocarcinoma Mimicking Vegetative Genital Herpes: A Case Report.

Colorectal cancer is the third most common cancer worldwide. Cutaneous metastases are rare and usually represent advanced disease. and their diverse clinical manifestations may mimic inflammatory or infectious dermatoses, leading to delayed diagnosis and poor outcomes. We present a case of a 70-year-old woman with a history of moderately differentiated rectal adenocarcinoma treated with neoadjuvant radiotherapy and surgery who developed metastatic disease with a KRAS G12V mutation. During follow-up, she presented with vulvar, perineal, inguinal, and gluteal erythematous papules, nodules, and simulating vesicles, initially misdiagnosed as an atypical herpetic infection. Histopathological examination of punch biopsies revealed gland-forming malignant epithelial cells consistent with cutaneous metastasis from colorectal adenocarcinoma. Cutaneous metastases from colorectal cancer show heterogeneous and sometimes rare presentations, including herpetiform and pseudotumoral patterns. Vulvar involvement is exceptionally uncommon therefore prompt recognition and histopathological confirmation are essential in patients with persistent or atypical lesions to avoid misdiagnosis and allow timely management.