Small intestine & ampulla

• Peutz-Jeghers polyposis syndrome is an autosomal dominant syndrome with variable penetrance and an incidence of 1 case in 50,000 - 200,000 births (Clin Gastroenterol Hepatol 2006;4:408)
• ~67% of patients present in the second to third decades of life and 33% present in first decade of life

• Diagnosis of a Peutz-Jeghers polyp requires endoscopy with polypectomy and histologic evaluation
• WHO diagnostic criteria for Peutz-Jeghers syndrome includes:
  • ≥ 3 histologically confirmed Peutz-Jeghers polyps
  • Any number of Peutz-Jeghers polyps with a family history of Peutz-Jeghers syndrome
  • Characteristic, prominent mucocutaneous pigmentation with a family history of Peutz-Jeghers syndrome
  • Any number of Peutz-Jeghers polyps and characteristic, prominent mucocutaneous pigmentation
• Reference: Gut 2010;59:975

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Contributed by Krutika S. Patel, M.B.B.S., M.D. and @SueEPig on Twitter

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• Mucosal prolapse polyp:
  • More common in rectosigmoid colon
  • Smooth muscle shows more disarray and is less compact than Peutz-Jeghers polyp
  • Smooth muscle wrapping around individual crypts favors mucosal prolapse
• Juvenile polyp:
  • Loose, edematous lamina propria with inflammation is a characteristic feature
  • Smooth muscle arborization is not a prominent feature
  • Marked cystic dilation of epithelial component is more common
  • Genetic testing shows germline mutations in SMAD4 or BMPR1A
• Inflammatory polyp:
  • Usually associated with branching and cystic dilatation of epithelial component with regenerative mucosa with reactive atypia
  • Edematous lamina propria with acute and chronic inflammatory infiltrate
• Sporadic hyperplastic polyp:
  • Uncommon, typically occurs in the second portion of the duodenum
  • Histologically resembles colonic microvesicular hyperplastic polyps with epithelial serrations, crypts with narrow bases, mucin droplets and bland cytology
  • Small case series showing association with mutations in BRAF V600E and KRAS (Hum Pathol 2011;42:1953)
• In addition to histology, clinical and family history often aid in the diagnosis; for Peutz-Jeghers polyps, as for other hamartomatous polyps with syndromic considerations, consultation with genetic counseling is recommended to gather family history and consider germline mutation analysis

Which of the following is true about the syndrome associated with the jejunal polyp shown above?

1. Associated with autosomal recessive inheritance pattern
2. Associated with germline mutations in SMAD4
3. Dysplasia is seen in a majority of these polyps
4. Histology is characterized by papillary architecture with arborizing compact bundles of smooth muscle
5. More commonly seen in the sigmoid colon

D. Histology is characterized by papillary architecture with arborizing compact bundles of smooth muscle. The image is of a Peutz-Jeghers polyp, which is morphologically characterized by tree-like arborizing smooth muscle cores dividing lobules of relatively normal glandular villous epithelium. Peutz-Jeghers polyposis syndrome patients have autosomal dominant germline mutation in STK11 (formerly LKB1). It most commonly affects the small bowel. Dysplasia is rare in Peutz-Jeghers polyps.

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Reference: Peutz-Jeghers polyp

The above small intestinal polyp is removed from a patient after an episode of intussusception. They are also noted to have perioral hyperpigmented spots. In which gene does this patient likely have a germline mutation?

1. APC
2. PTEN
3. SMAD4
4. STK11 (formerly LKB1)

D. STK11 (formerly LKB1). The above polyp is consistent with a Peutz-Jeghers type polyp. Germline mutations in tumor suppressor gene serine / threonine kinase 11 (STK11 - formerly called LKB1) are found in up to 90% of cases and is inherited in an autosomal dominant fashion. Patients with this syndrome often have perioral hyperpigmented macules. SMAD4 mutations are associated with juvenile polyps. APC mutations are seen in familial adenomatous polyposis. And PTEN mutations are associated with Cowden syndrome.

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Reference: Peutz-Jeghers polyp