Vascular pseudoinvasion in a solitary Peutz-Jeghers polyp in the ileum.

A Peutz-Jeghers polyp (PJP) is a hamartomatous lesion characterized by arborescent smooth muscle bundles covered with mucosa native to the site of involvement. PJPs in the small intestine may represent misplacement of non-neoplastic epithelium into the submucosa, muscularis propria and subserosa. Although epithelial misplacement in PJPs is a well-documented phenomenon, pseudoinvasion even into the vascular space in PJPs has not previously been reported. We report a case of a 22-year-old Japanese woman with a solitary PJP in the ileum. The ileal PJP in this patient showed epithelial herniation even into the vascular space. All the herniated epithelium, including the epithelial components invaginated into the vascular space, demonstrated features of pseudoinvasion, that is, presence of normal small intestinal type mucosa accompanied by the lamina propria, absence of any stromal desmoplastic reaction, and retention of the basal-luminal gradient. Pathologists must be aware of the possibility of vascular pseudoinvasion in small intestinal PJPs to avoid overdiagnosis of carcinoma and resulting unnecessary major surgery.