Abstract
BACKGROUND: Serum carcinoembryonic antigen levels are often elevated in patients with malignant diseases. However, the etiology of elevated serum carcinoembryonic antigen levels may be extremely difficult to determine considering that this finding may occasionally occur in patients with benign diseases. Apocrine hidrocystomas, which are typically small and found on the face, are benign cystic lesions of apocrine sweat glands. CASE PRESENTATION: A 58-year-old Japanese man was referred to us because of high serum carcinoembryonic antigen levels (15.9 ng/mL) found incidentally during a routine medical checkup. A physical examination revealed a hemispherical mass approximately 5 cm in diameter on his left thigh. Magnetic resonance imaging of the region showed a multilocular cystic mass with clear margins and a smooth surface, suggesting a cystic tumor. He underwent local mass resection. Pathological examination of the resected mass revealed an apocrine hidrocystoma with luminal cells, which tested immunohistochemically positive for carcinoembryonic antigen. Postoperatively, serum carcinoembryonic antigen levels returned to normal. This report is the first to describe an apocrine hidrocystoma associated with high serum carcinoembryonic antigen levels. CONCLUSIONS: An apocrine hidrocystoma can cause elevation of serum carcinoembryonic antigen levels. Despite its rarity, apocrine hidrocystoma should be considered in the differential diagnosis of conditions causing high serum carcinoembryonic antigen levels. In addition, skin diseases deserve more careful attention for patients with high serum carcinoembryonic antigen levels.