Supplementary Material for: When STI Treatment Fails: A Rare Dermatological Presentation of Lung Cancer –A Case Report

Introduction:
Cutaneous metastases are uncommon but may represent the first clinical manifestation of internal malignancies. In men, lung cancer is the most frequent source of such lesions. Due to their variable presentation, these metastases can mimic sexually transmitted infections (STIs) and delay the correct diagnosis.

Case Presentation:
A 46-year-old male presented with a painless ulcerative lesion in the right inguinal region that had persisted for one month. Despite broad-spectrum antibiotic therapy, there was no clinical improvement. Histopathological and immunohistochemical evaluation of a skin biopsy revealed positivity for CK7 and TTF-1, consistent with metastatic lung adenocarcinoma. Subsequent imaging and bronchoscopic biopsy confirmed non-mucinous adenocarcinoma of the lung.

Conclusion:
This case highlights the importance of considering internal malignancies in the differential diagnosis of genital and inguinal ulcerative lesions, particularly when conventional treatments fail. Early biopsy and immunohistochemical analysis are essential for accurate diagnosis and timely management.