Gastrointestinal Polyposis Syndromes Joel K. Greenson, M.D. Professor of Pathology University of Michigan Medical School Ann Arbor, Michigan, USA 48109

Familial Adenomatous Polyposis (FAP)

FAP is an autosomal dominant condition due to a mutation in the APC gene on chromosome 5. 25-33% of FAP cases are due to spontaneous mutations so a family history may be negative in many cases. Virtually all FAP patients will develop invasive colorectal by age 40 if a colectomy is not preformed. Classic FAP patients have hundreds if not thousands of colonic adenomas. They also get gastric and duodenal adenomas as well as gastric fundic gland polyps. FAP patients also have congenital hypertrophy of the retinal pigment epithelium which can be seen on fundoscopic exam. There are some phenotypic variations within FAP such as patients with Gardner syndrome who also have desmoid tumors and osteomas of the mandible and patients with Turcot syndrome who also have brain tumors (medulloblastomas in children). Some cases of Turcot syndrome may also be due to Lynch syndrome (glioblastoma). Hepatocellular carcinomas, Hepatoblastomas and papillary thyroid carcinomas have also been associated with FAP as have epidermal , lipomas, fibromas and nasopharyngeal angiofibromas.

Some patients with APC mutations at either end of the gene have an attenuated phenotype with only 10 – 100 adenomas that may not show up until after age 45. Given the older age and lessor number of polyps, these patients may be more difficult to identify as having FAP. The polyps are often right-sided in attenuated FAP such that sigmoidoscopic screening could miss them completely.

Histologically the adenomas in FAP are identical to sporadic adenomas. The hallmark of the disease is the presence of unicryptal adenomas that can be identified by submitting sections of mucosa embedded en face (so-called Bussey section named after one of the pioneers of FAP research Dick Bussey). The presence of dysplasia on the top of a fundic gland polyp should also raise concern about FAP (especially if present in multiple polyps), although one can rarely get dysplasia in sporadic fundic gland polyps.

MUTYH-associated polyposis (MYH)

MYH is an autosomal recessive disorder that clinically mimics attenuated FAP. Patients typically have between 20 to 100 adenomas with the mean age of diagnosis being 45. Duodenal adenomas can also be seen, but the other extra intestinal tumors seen in FAP are not seen in MYH.

MUTY homologue is an enzyme that repairs damage done to DNA by oxidation of guanine. When guanine is oxidated it will bind to adenine rather than cytosine, leading to G:C to T:A tranversion mutations. MUTY excises the oxidated guanine to prevent these tranversions. When this is knocked out, one can find numerous G:C to T:A tranversions within the adenomas. Histologically there are no features that allow one to identify MYH polyps from sporadic adenomas.

Polymerase Epsilon and Polymerase Delta Polypsosis Syndromes

These are recently described polyposis syndromes that phenotypically resemble attenuated FAP. They are inherited in an autosomal dominant fashion with fairly complete penetrance. As these polymerases aid in DNA proofreading, on can find multiple transversions, both G:C to T:A and T:A to G:C. There appears to be an increased risk of endometrial carcinoma in women with the syndromes.

Peutz-Jeghers Syndrome (PJ)

PJ is one of several hamartomatous polyposis syndromes that affect the GI tract. Patients with PJ typically have characteristic pigmentation of the lips, oral and genital mucosa as well as numerous polyps scattered throughout the gut. It is inherited as an autosomal dominant condition. The diagnosis of PJ syndrome may be made when one of the following is present: Two or more histologically confirmed PJ polyps, any number of PJ polyps in someone with a family history of PJ, mucocutaneous pigmentation in someone with a family history of PJ, any number of PJ polyps in someone with mucocutaneous pigmentation. Despite the fact the polyps are “”, patients with PJ are at risk for a large number of epithelial including carcinomas of the colon, small bowel, stomach, , breast and Gyn tract. Ovarian sex cord tumors with annular tubules (SCTATs) are a characteristic tumor seen in some female PJ patients. Female PJ patients are also at risk for mucinous tumors of the ovaries and fallopian tubes as well as adenoma malignum of the cervix. A study by Montgomery and colleagues found that even patients with only a single PJ type polyp who did not fit the WHO criteria of having PJ syndrome had an increased cancer risk similar to patients with the syndrome, suggesting that one may only need a single PJ polyp to have the syndrome.

The gene for PJ is LKB1 (also known as STK11 – the only thing worse than having one string of letters and numbers to try and remember is to have two equally useless ones for the same thing). LKB1 is a serine-threonine kinase that is thought to behave like a tumor suppressor gene. It is important in controlling cell proliferation and regulates the mTOR pathway.

PJ polyps have a characteristic pattern of arborizing smooth muscle best appreciated at low-power. The epithelium is benign although reactive atypia may be present. One must be aware that epithelial misplacement is common in these polyps (do not over-diagnose cancer in these lesions). While small bowel polyps typically have abundant branching smooth muscle, this may be much less apparent in gastric or colonic polyps, especially if the polyps are small. One must also be wary of overcalling mucosal prolapse polyps as PJ polyps. While it is natural to assume that PJ polyps go through a -dysplasia-carcinoma sequence, there is strikingly little data to support this (only very rare case reports). More recent insight into the molecular pathogenesis of PJ syndrome suggests that there is an expanded stem cell compartment present in many epithelial systems which predisposes to benign polyps as well as cancers, but not necessarily as a step-wise process. This new data suggests that the smooth muscle changes in these polyps are simply related to mucosal prolapse due to epithelial and are not really part of the polyp and hence these polyps really are not hamartomas (a conclusion I find hard to believe considering that other small bowel polyps don’t get prolapse changes, while nearly any type of polyp other than PJ polyps found in the left colon does). The majority of PJ polyps are found in the small bowel but colonic, gastric, , bronchial and even ureteral/urinary bladder polyps have been described. A recent study by Montgomery and colleagues found that the reproducibility of distinguishing gastric PJ polyps from juvenile and hyperplastic polyps was quite poor without clinical history.

Juvenile Polyposis Syndrome (JPS)

Juvenile polyposis is another autosomal dominant hamartomatous polyp syndrome that harbors an increased risk of cancer. Juvenile polyposis is diagnosed clinically when any one of the following criteria is met: >3-5 juvenile polyps in the colorectum; juvenile polyps throughout the intestinal tract; or any number of juvenile polyps in the setting of a family history of JPS. Unlike PJ, sporadic juvenile polyps are not uncommon, occurring in up to 2% of children. The absolute number of juvenile polyps required to have the syndrome is a moving target, as 3, 5 and 10 have all been used as cut-off values. There appear to be several different genes involved in JPS as 50 – 60 % of patients have a germline mutation in either SMAD4 or BMPR1A. Both of these genes are involved in the transforming growth factor beta (TGF)/bone morphogenic protein signaling pathway. Some patients with juvenile -type polyps have germline PTEN mutations, however, more recent evidence suggests this is not JPS but rather a manifestation of PTEN-hamartoma tumor syndrome (Cowdens syndrome, Bannayan-Riley-Ruvalcaba syndrome). Recently a third gene (ENG) has also been discovered to lead to JPS, it is also involved in the TGF-beta pathway.

Endoscopically juvenile polyps are spherical and often pedunculated. They are typically more common in the colon and , although patients with SMAD4 mutations are more likely to have gastric and small intestinal polyps as well. Histologically these polyps have cystically dilated glands associated with an inflamed lamina propria. Erosions and surface ulcerations are common, which often leads to reactive atypia. Care must be taken not to overcall these reactive changes as dysplasia. Unlike PJS, true dysplasia and even carcinoma is not uncommonly seen developing in juvenile polyps. The overall risk of developing in JPS may be as high as 40-70%. There is probably an increased risk of gastric and small intestinal cancer and perhaps pancreas cancer as well. It appears the rate of dysplasia in juvenile polyps is similar in patients with SMAD4 or BMPR1A mutations. Juvenile polyps with SMAD4 mutations were found to have a higher crypt to stroma ratio than juvenile patients with BMPR1A mutations.

Small juvenile polyps can be impossible to distinguish from run of the mill inflammatory pseudopolyps. The GI polyps seen in Cowden/PTEN-hamartoma can also be identical to juvenile polyps, hence the confusion and overlap between the two syndromes. The polyps seen in Crohnkhite –Canada syndrome can also be identical to juvenile polyps although they tend not to be pedunculated in CC. Juvenile polyps lack the arborizing smooth muscle seen in PJ polyps. There are also case reports of JPS patients that had mucosal ganglioneuromas. It is unclear whether these cases were truly JPS or another syndrome such as Cowdens.

Cowden / PTEN-hamartoma Syndrome

Cowden’s syndrome is a rare autosomal dominant condition due to a mutation in the PTEN gene. Clinical features include mucocutaneous lesions, macrocephaly and an increased risk of benign and malignant disorders of the breast, thyroid and endometrium. Whether there is an increased risk of colon cancer is debatable. Bannayan-Ruvalcaba-Riley Syndrome (BRRS) patients have hamartomatous GI poylps,lipomas, hemangiomas, developmental delay and pigmented macules on the glans penis. Additional lesions seen in the PTEN- hamartoma syndrome include facial trichilemmomas, acral keratosis, breast and endometrial carcinomas and follicular carcinomas of the thyroid.

The polyps in the GI tract are poorly characterized and easily missed. In my own experience many of the colonic polyps just look like focal crypt distortion or small inflammatory pseudopolpys. Larger lesions have been described that mimic both juvenile and PJ polyps. Adenomas, hyperplastic polyps and ganglioneuromas have also been described in Cowden’s patients. Esophageal glycogenic acanthosis has also been reported in Cowdens’ patients.

Hyperplastic polyposis syndrome (HPS):

Hyperplastic polyposis syndrome is a bit of a confusing term as many of the original cases of this were clearly describing serrated polyps that today would be called sessile serrated adenomas. Factor in the presence of another syndrome with considerable overlap called hereditary mixed polyposis and the waters get very muddy. There are also reports of “serrated polyposis”. If all of this isn’t confusing enough, a number of different genes have been implicated for these syndromes (PTEN, EBPH2, MUTYH, BMPR1A) but none of these has been substantiated. Both autosomal dominant and recessive inheritance patterns have been reported.

The current definition of HPS is at least five histologically diagnosed serrated polyps proximal to the sigmoid colon, of which two are >10 mm in diameter, or (ii) >20 serrated polyps in a pancolonic distribution, or (iii) any number of serrated polyps occurring proximal to the sigmoid colon in an individual who has a first- degree relative with HPS. Colectomy specimens in patients with this syndrome typically have shown multiple adenomas as well as serrated poylps.

Hereditary Mixed Polyposis Syndrome

In hereditary mixed polyposis patients have a mixture of serrated polyps, adenomas and juvenile polyps. Given the presence of juvenile polyps in mixed polyposis, it should not seem surprising that BMPR1A has been implicated as one of the genes responsible for this syndrome. Another gene called CRAC1 has also been implicated in at least one kindred of patients with hereditary mixed polyposis (finally a gene who’s name you might be able to remember). Most recently a small duplication in an area upstream of the GREM1 gene on chromosome 15 has been implicated in a large Ashkenazi kindred with mixed polyposis syndrome.

Lynch Syndrome (LS) also known as HNPCC

Lynch syndrome (or what used to be called hereditary non-polyposis colorectal cancer syndrome – HNPCC) is an autosomal dominant disorder that is the most common heritable cause of cancer. It accounts for 3-5% of all colon cancers and is also associated with of the endometrium, ovary, stomach, small bowel, pancreas, hepatobiliary tract, upper urothelial tract, brain (Turcot) and skin (sebaceous tumors in Muir-Torre). There are rare cases of children with biallelic MMR mutations. They present in early childhood with leukemia or lymphoma, café-au-lait spots and GI tract malignancies

Lynch syndrome was first described by Warthin (the first chairman of pathology at the University of Michigan) in 1913. We now know that the syndrome is caused by mutations in one of four major mismatch repair (MMR) genes, namely MLH1, MSH2, MSH6 and PMS2 (although MSH3 may be involved in a small number of cases). Failure of DNA mismatch repair leads to tumors that have a high level of microsatellite instability (MSI-H). 90-95% of colorectal tumors that arise in LS have microsatellite instability which can be easily detected by comparing normal and tumor formalin-fixed paraffin-embedded tissue samples. In addition, immunohistochemistry for the 4 main mismatch repair (MMR) proteins is readily available. Immunostaining also has about a 5% false negative rate in detecting LS, so neither test is perfect. The question now facing pathologists is which tests should be used to screen for lynch syndrome and which tumors should be tested. Approximately 15% of all colorectal cancers are MSI-H, but the majority of these tumors are sporadic secondary to methylation of MLH1. These sporadic tumors are often seen in the right colon of older female patients. Determining whether an MSI-H tumor is due to LS or methylation often requires additional testing for either Braf V600E mutations and/or methylation. It turns out that LS tumors do not have BRAF V600E mutations while the majority of sporadic MSI-H tumors due. The precursor lesion for LS tumors is an adenoma, while sporadic MSI-H tumors typically arise via the serrated pathway.

The revised Amsterdam criteria (listed below) is a useful screen to look for LS patients At least three relatives with an hereditary nonpolyposis colorectal cancer (HNPCC)- associated cancer [colorectal cancer, endometrial, stomach, ovary, ureter/renal pelvis, brain, small bowel, hepatobiliary tract, and skin (sebaceous tumors)]: 1 One is a first-degree relative of the other two; 2 At least two successive generations affected; 3 At least one of the syndrome-associated cancers should be diagnosed at <50 years of age; 4 FAP should be excluded in any colorectal cancer cases; Tumors should be verified whenever possible.

There are a number of phenotypic differences between colorectal cancers that are MSI-H versus those that are stable. MSI-H tumors are often right-sided, are well or poorly-differentiated, have mucinous or signet-ring differentiation, have a bushing border, and have a brisk host response (both a Crohn’s like reaction and tumor infiltrating lymphocytes (TILs)). MSI-H tumors have also been shown to have a plasma cell rich stroma and to have histologic heterogeneity while lacking dirty necrosis. The single best histologic predictor of MSI-H is the presence of 2 or more TILs per high-powered field. One can use these histologic features to try and decide which tumors should be sent for MSI and MMR IHC. Two different studies have shown that about 50% of colon cancers will have no phenotypic findings to suggest they are MSI-H, and that there is less than 5% likelihood that such tumors will be MSI-H upon testing. The following website was developed by reviewing the histology and doing MSI testing on1649 consecutive colorectal cancers in Northern Israel. By entering the age of the age of the patient, site of the cancer and a few pathologic variables, one can predict the likelihood of a tumor being MSI-H.

http://sitemaker.umich.edu/gruber.lab/files/msi_pre.htm

While histology can certainly be a guide, there is no substitute for clinical history (A young patient with a strong family history should be tested regardless of what the tumor looks like).

Adenomas in LS also have some distinguishing histological features. Compared to sporadic adenomas, Lynch adenomas have more adenoma infiltrating lymphocytes (>5/high-power field) and fewer apoptotic bodies. These changes are not entirely specific, as 12% of sporadic adenomas have also been found to have >5 lymphs/hpf).

The revised Bethesda guidelines have been developed to determine which tumors should be tested (listed below): 1. Colorectal cancer diagnosed in a patient who is <50 years of age. 2. Presence of synchronous or metachronous colorectal, or other syndrome- associated tumors regardless of age. 3. Colorectal cancer with microsatellite instability-high (MSI-H) histologyc diagnosed in a patient who is <60 years of age. 4. Colorectal cancer or syndrome-associated tumor diagnosed under age 50 years in at least one first-degree relative. 5. Colorectal cancer or syndrome-associated tumor diagnosed at any age in two first- or second-degree relatives.

Several studies have looked at the cost effectiveness of screening for Lynch syndrome and all of them have advocated testing every colon cancer regardless of histology or clinical scenario. Given our march towards personalized medicine, I suspect such global testing will rapidly become the norm.

Table 1: Immunohistochemical Results for MMR stains IHC IHC IHC IHC MLH1 PMS2 MSH2 MSH6

MLH1 Loss Loss Positive Positive Mutation PMS2 Positive Loss Positive Positive Mutation

MSH2 Positive Positive Loss Loss Mutation

MSH6 Positive Positive Positive Loss Mutation

A.R. Sepulveda, Medscape Pathology; http://cme.medscape.com/viewarticle/571610

References:

Familial Adenomatous Polyposis (FAP)

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MUTYH-associated polyposis (MYH) Al-Tassan N, Chmiel NH, Maynard J, et al. Inherited variants of MYH associated with somatic G:C→T:A mutations in colorectal tumors. Nat Genet. 2002;30:227– 232.

Polymerase Epsilon and Polymerase Delta Polypsosis Syndromes

Briggs S, Tomlinson I. Germline and somatic polymerase ε and δ mutations define a new class of hypermutated colorectal and endometrial cancers. J Pathol. 2013 Jun;230(2):148-53. Peutz-Jeghers Syndrome (PJ) McGarrity TJ, Amos C. Peutz-Jeghers syndrome: clinicopathology and molecular alterations. Cell Mol Life Sci. 2006 Sep;63(18):2135-44.

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Burkart AL, Sheridan T, Lewin M, Fenton H, Ali NJ, Montgomery E. Do sporadic Peutz-Jeghers polyps exist? Experience of a large teaching hospital. Am J Surg Pathol. 2007 Aug;31(8):1209-14.

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Juvenile Polyposis Syndrome (JPS) van Hattem WA, Langeveld D, de Leng WW, Morsink FH, van Diest PJ, Iacobuzio-Donahue CA, Giardiello FM, Offerhaus GJ, Brosens LA. Histologic variations in juvenile polyp phenotype correlate with genetic defect underlying juvenile polyposis. Am J Surg Pathol. 2011 Apr;35(4):530-6. van Hattem WA, Brosens LA, de Leng WW, Morsink FH, Lens S, Carvalho R, Giardiello FM, Offerhaus GJ. Large genomic deletions of SMAD4, BMPR1A and PTEN in juvenile polyposis. Gut. 2008 May;57(5):623-7. Epub 2008 Jan 4.

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Cowden Syndrome

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Hyperplastic polyposis syndrome:

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Boparai KS, Dekker E, Polak MM, Musler AR, van Eeden S, van Noesel CJ A serrated colorectal cancer pathway predominates over the classic WNT pathway in patients with hyperplastic polyposis syndrome. Am J Pathol. 2011 Jun;178(6):2700-7.

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Hereditary Mixed Polyposis Syndrome

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Lynch Syndrome

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