Squamous cell carcinoma (SCC) antigen is a reliable tumor marker for various cancers, including cervical cancer and lung cancer, and was recently reported to correlate with the severity of inflammatory skin diseases such as atopic dermatitis. Herein, we present a case of a 47-year-old female patient who presented with acute abdomen rupture due to a mature cystic teratoma of the ovary, approximately 11 cm in diameter on imaging examination, prompting emergency laparoscopic surgery. The patient had no symptoms of atopic dermatitis. The operative findings showed no evidence of torsion, but the membrane was partially ruptured, leading to the leakage of the cyst contents. The operation was completed after excising the adnexa and intraperitoneal lavage. The postoperative results revealed a markedly high serum SCC antigen level of 55.3 ng/dL, which was normalized at 2 months postoperatively. Postoperative histopathological examination revealed no squamous cell carcinoma component but a marked lymphocytic infiltrate under the squamous epithelium, suggesting a high degree of inflammation. Additionally, immunostaining demonstrated a cluster of differentiation (CD) 8+ lymphocyte predominance over CD4+ lymphocytes, similar to the histology of atopic dermatitis. Altogether, our findings suggest that the abnormally high SCC antigen levels might be attributed to the presence of severe inflammation in the mature cystic teratoma rather than an underlying malignancy and support the notion that SCC antigen may be a useful marker beyond its established role in cervical and lung cancers.