Variant type of teratoma appearing as a primary solid dermoid tumor in the rectum: report of a case.

We report herein the rare case of a 39-year-old woman found to have a primary solid dermoid tumor in the rectum. The patient presented after noticing a small amount of anal bleeding, and physical examination revealed a walnut-sized hard tumor, palpable in the anterior rectum, located about 9 cm from the anal verge. Morphologic examinations revealed a polypoid lesion with some hair surrounded by rectal mucosa, and four biopsy specimens from the lesion showed normal squamous epithelium. The tumor, which measured 2.5 x 2.1 x 1.3 cm, was removed by endoscopic polypectomy. Microscopically, the tumor was diagnosed as a solid dermoid tumor without a cyst, a variant type of mature teratoma or dermoid cyst. Since 1914, only 12 such cases, including ours, have been reported in Japan. The clinical features and diagnostic and therapeutic methods applied thereto are discussed.