Cutaneous Metastasis as the First Sign of Gastric Signet Ring Carcinoma: A Case Report of an Uncommon Clinical Presentation and a Brief Review of the Literature

Cutaneous metastasis as the initial presenting sign of an underlying gastric signet ring cell carcinoma (SRCC) is very rare and easily confused with benign dermatologic disease. We present a 46-year-old female who developed multiple firm, erythematous nodules over the breast, shoulder, and buttocks over 3 months. The skin lesions were initially treated as soft-tissue infections, but there was no response to therapy. A core biopsy of the skin ultimately disclosed metastatic adenocarcinoma with prominent intracytoplasmic mucin and signet-ring morphology; similar malignant cells were subsequently identified in pleural and ascitic fluids.Immunohistochemical (IHC) studies demonstrated a CK7-positive, CK20-negative pattern with strong mucin expression and weak CDX2 labeling, consistent with an upper gastrointestinal primary. Cross-sectional imaging identified diffuse gastric wall thickening consistent with lienitis plastica, peritoneal and pleural involvement, and distant osseous metastases. Poorly differentiated signet ring cell gastric adenocarcinoma was confirmed through endoscopic biopsies, defining stage IV disease. Fluoropyrimidine-platinum chemotherapy and then second-line irinotecan failed to halt disease progression in this patient; her cancer reflected the classic chemo resistant behavior for this histologic subtype. She survived approximately two years after diagnosis.This case thus underlines the need to include metastatic cancer in the differential diagnosis of any persisting or atypical skin nodule: an approach which calls for early biopsy and well-thought-out interpretation of immunophenotyping findings, followed by timely integration of imaging to disclose the silent gastric malignancy and guide management appropriately in a multidisciplinary manner.