BACKGROUND Metastatic skin cancers are relatively rare dermatological malignancies. They usually present as nodules, erythematous lesions, scar-like lesions or other lesion types. Signet-ring cell carcinoma (SRCC) is an uncommon histological type of gastric cancer that usually behaves aggressively and has a poor prognosis. Skin metastasis may be the first sign of clinically silent visceral cancer or recurrence of an internal malignancy. CASE SUMMARY Herein we report on the case of a 55-year-old man with edema of a lower extremity as the primary symptom which progressed from local to generalized pitting edema in the year following skin involvement. Pathological evidence from gastroscopic specimens and subcutaneous tissue biopsy showed typical signet-ring cells and gland-like structures. Consistently, immunohistochemical analysis revealed positive pan-cytokeratin expression in tumor cells. A diagnosis of gastric SRCC with skin metastasis was established. Moreover, lymphoscintigraphy showed an obvious accumulation of radiotracer on the anterior and posterior sides of the right leg which indicated lymphedema. We reviewed the relevant literature on subcutaneous metastases of gastric SRCC. CONCLUSION This rare case emphasizes the importance of physical examination as it may help elucidate the etiology of edema.