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A 50-year-old Japanese man had colonoscopy as a screening test for colorectal cancer. A pedunculated polyp, approximately 18 mm in diameter, was noted in the sigmoid colon. At chromoendoscopy, the polyp was lobulated with grooves as shown in Figure 1. The polyp was removed by loop diathermy and, histologically, was composed of branching bundles of smooth muscle fibers covered by elongated crypts without dysplasia (Figure 2). The diagnosis was that of a solitary Peutz-Jeghers-type hamartoma of the colon. Four years previously, he had been treated by distal gastrectomy for an early gastric cancer. Colonoscopy was performed at that time but no polyps or other lesions were found. Furthermore, there were no cutaneous manifestations of Peutz-Jeghers syndrome and no abnormalities were detected in the small bowel on a follow-through examination.

Non-neoplastic polyps of the colon can be categorized as hyperplasias, inflammatory polyps, hamartomas, heterotopias and miscellaneous lesions. The most frequent non-neoplastic polyp is a hyperplastic polyp, sometimes called a metaplastic polyp. Another significant group are various inflammatory and postinflammatory polyps including an entity of uncertain etiology called an inflammatory fibroid polyp. Hamartomatous polyps contain a disorganised but mature mixture of specialized cells that normally reside in the colon. Examples include the Peutz-Jegher polyp, juvenile polyp, Cowden's disease polyp, ganglioneuroma and Cronkhite-Canada polyp. Solitary Peutz-Jeghers-type polyps have been described previously but appear to be rare. Although the pathogenesis of these polyps remains unclear, there is no evidence that patients with solitary polyps form part of the Peutz-Jeghers syndrome. At endoscopy, Peutz-Jegher-type polyps can have a similar appearance to juvenile polyps and inflammatory fibroid polyps. Histologically, Peutz-Jeghers-type polyps consist of normal colonic glands and lamina propria that is arranged into lobules by branching bands of smooth muscle. In contrast, juvenile polyps have an expanded, edematous and inflamed lamina propria that contains distorted glands, many showing cystic dilatation. For inflammatory fibroid polyps, the major feature is vascularized fibrous tissue that is infiltrated by a variety of chronic inflammatory cells, sometimes with prominent eosinophils.