Recent advances on Colo-rectal carcinoma

Dr. Samriddhi Karki1st year Resident

Department of Pathology

• Introduction • Epidemiology • Etiology• MOLECULAR PATHOGENESIS• Clinical features• Morphology• Diagnostic modalities• Staging and grading• Spread and Metastasis• Treatment• Prognosis

INTRODUCTION•Third most common type of cancer and second most

frequent cause of cancer-related death.

•Most curable form of carcinoma of the gastrointestinal tract.

•Usually begins as a noncancerous polyp that can, over time, become a cancerous tumor.

•Males and females are equally affected.

•Mean age : 62 year

EPIDEMIOLOGY•Worldwide distribution

•Highest incidence rates in ▫United States▫Canada▫Australia▫New Zeaand▫Denmark ▫Sweden, and ▫Other developed countries

•Colorectal Carcinoma (CRC) among Nepalese young adults accounts for a high incidence (28%) of all CRC cases.

•Although right sided colonic cancer has been increasing, rectum is

the commonest site.

Asian Pacific Journal of Cancer Prevention, Vol 13, 2012

ETIOLOGY1. Dietary factors2. Obesity 3. Smoking4. Inflammatory bowel disease

5. Polyps

6. Pelvic Irradiation

7. Genetic factors▫Hereditary non-polyposis colorectal cancer (HNPCC) -

Lynch syndrome▫Familial adenomatous polyposis (FAP)

Hereditary Non-polyposis colorectal cancer ( HNPCC)

•Autosomal dominant disorder.

•Cancers at several sites ▫Colorectum▫Endometrium ▫Stomach ▫Ovary ▫Uterus ▫Brain ▫Small bowel ▫Hepatobiliary▫Skin

Features of CRC in HNPCC•Young age•Right –sided location•Mucinous features•Poor differentiation •Lymphocytic infiltration •Lack of necrosis

Familial adenomatous polyposis (FAP)

•Autosomal dominant disorder.

•Numerous ( 100- 1000) colorectal adenomas.

•Mutation of the adenomatous polyposis coli (APC) gene.

• In left untreated colorectal carcinoma ( 100%) , before age 30.

MOLECULAR PATHOGENESIS•TWO distinct genetic pathways .

1. APC / β- catenin pathway▫ Associated with WNT signaling pathway

and the chromosomal instability pathway.

2. Microsatellite instability pathway

▫ Associated with defects in DNA mismatch repair

APC / β- catenin pathway•APC tumor suppressor gene (5q21)•Downregulate growth promoting

signals (β-catenin)•Component of WNT signaling pathway.

•Catenins proteins found in complexes with cadherin cell adhesion molecules.

•β-catenin participates in the WNT signaling pathway as a growth promoting signals.

WNT signaling pathway•Network of proteins that passes signals from

cell surface receptors to the nucleus through cytoplasm leading to expression of target genes (transcription regulator genes- c MYC)

•Major role in controlling cell fate, adhesion, and cell polarity during embryonic development.

•WNT signaling is also required for self –renewal of the hematopoetic stem cells.

Chromosomal instability pathway(CIN)

• Increased rate of chromosome missegregation in mitosis .

• Due to – Gain / loss of chromosome ( aneuploidy)– Gross chromosomal rearrangements (GSM)

•Earliest event involved in CIN is APC gene mutation ( 80%)▫K-RAS mutation▫P53 gene mutation

•Late event : DCC (deleted in colonic carcinoma) gene mutation

•Advanced event : DPC4/ SMAD4 mutation (18q21)

CIN forms the basis of Adenoma -Carcinoma

Sequence

Adenoma-carcinoma sequence

MICROSATELLITE INSTABILITY pathway (MSI )

1. Satellite DNA?2. Microsatellite DNA?3. Why is it more liable to be unstable ?4. How this instability leads to colorectal

carcinoma ?

Satellite DNA• Satellite DNA  is composed of tandemly repeating DNA ( non - coding regions)

• Tandem repeats occur in DNA  when a pattern of two or more nucleotides is repeated.

A-T-T-C-G-A-T-T-C-G-A-T-T-C-G

Type of DNA repeat No. of nucleotide repeat

1. Satellite 5-200

2. Minisatellite

a. Hypervariable 10-60

b. Telomeric 6

3. Microsatellite 1-4

a. Monomorpic

b. Polymorphic

•Microsatellite DNA : If the number of nucleotide repeat is 1-4▫Dinucleotide repeat:

When exactly two nucleotides are repeated. Eg: ACACACAC Such regions in DNA are commonly affected in HNPCC.

• Microsatellites are more prone to get unstable compared to other neutral regions of DNA

• This instability is due to any errors , most likely error is ▫Slippage during DNA replication .

• Such error is normally repaired by Mismatch repair enzymes which are encoded by MisMatch repair genes.

Defect in MMR gene

Reduced capacity of cells to repair specific types of DNA damage

Increased rate of mutation accumulation in microsatellite DNA

Mismatch repair genes•MSH2 (2p21) , MSH3, MSH4, MSH5, MSH6•MLH1(3p21.3), MLH2, MLH3•PMS1, PMS2

•As majority of microsatellites are located in the non-coding region, these mutations are generally silent.

•Some microsatellites which are present in the coding region of the gene are involved in the regulation of cell growth , like those encoding ▫Type II TGF-ß receptor▫Proapoptotic protein BAX

Defect in MMR genes •Mutation HNPCC•CpG island Hypermethylation in MMR genes Sporadic CCR

CpG Island Hypermethylation •What is CpG?•Terms like : CpG site and CpG Island?•What is methylation?•What is hypermethylation ?•How hypermethylation leads to

carcinoma?

•CpG sites:▫Regions of DNA  where a cytosine occurs

next to a guanine. ▫DNA methylation occurs at these sites by an

enzyme called DNA methyltransferases.

• In humans, 80 to 90% of all CpGs are methylated.

•This methylation results in the conversion of the cytosine to 5-methylcytosine.

• The remaining 10% non-methylated CpGs  are grouped in a cluster forming CpG island , and is usually located in the promoter regions towards 5’ end.

• The unique property of CpG island is that it is unmethylated in the germ line.

•Methylation of CpG island within the promoters of genes silencing of tumor suppressor genes Cancer

Microsatellite instability

MSI testing •MSI can be detected by PCR amplification of

microsatellite loci in DNA extracted from CRC specimens .

• Newer tests: Nucleic acid flourescence labelling, laser scanning , flourescence PCR amplification .

• To identify the risk for hereditary cancer and predict the outcome of CRC.

•To detect MLH1 and MSH2 germline mutations .

The Bethesda GuidelinesMSI testing is recommended in people with any of the following features :

1. Cancer in families that meet Amsterdam criteria.

2. Two HNPCC- related cancers

3. A first degree relative with CRC and/or HNPCC- related extracolonic cancer and/or colorectal adenoma diagnosed under 40yr.

4. Right-sided CRC with an undifferentiated pattern on HPE.

5. Signet-ring cell type CRC diagnosed under 45yr.

6. Adenomas diagnosed under 40 yr.

CLINICAL FEATURES•Asymptomatic for years.

• Left sided colonic carcinomas▫occult bleeding▫changes in bowel habit▫crampy left lower quadrant discomfort

•Right sided colonic carcinomas▫ fatigue▫weakness▫ iron deficiency anemia

(Anemia in females may arise from gynecologic causes, but it is a clinical maxim that iron deficiency anemia in an older man means gastrointestinal cancer until proved otherwise)

MORPHOLOGY•50% rectosigmoid area (involvement of the proximal colon is increasing)

•Right-sided tumors more common in the▫elderly▫blacks▫patients with diverticular disease

GROSSA. PROXIMAL COLON •Polypoid:▫Bulky mass, well-defined/ rolled margins and a

sharp dividing line with the normal bowel.

•Ulcerative:▫Less elevated surface and is centrally ulcerated

•These tumors rarely cause obstruction

B. DISTAL COLON

•Annular lesions producing “napkin – ring” constrictions and luminal narrowing .

•These tumors can cause obstruction.

MICROSCOPIC

•All colorectal carcinomas looks similar.

•Almost all – ADENOCARCINOMAS secreting variable amounts of mucin.

•Ranges from well-differentiated to undifferentiated, frankly anaplastic masses.

• Tall columnar cells resembling dysplastic epithelium as in adenomas.

• Inflammatory infiltrations (lymphocytes, plasma cells, eosinophils, histiocytes ) are prominent at the edge of the tumor. 

• Poorly differentiated tumors might form few GLANDS.

• Rarely, the tumor stroma may exhibit metaplastic bone formation

Well - differentiated Poorly differentiated

Other microscopic

variants

Mucinous

Signet Ring

Medullary

Serrated

Squamous differentiati

onTrophoblastic

differentiation Hepatoid

Basaloid

Neuro-endocrine

Glassy cell

Oncocytic

Micro-papillary

Anaplastic

Mucinous adenocarcinoma•15 % of all CRCs•Common in

rectum.•Microscopically :

more than 50% extracellular mucin

•High association with MSI

•Worse prognosis.

Signet ring adenocarcinoma•Rare•Microscopically :

more than 50% intracellular mucin

•About one third cases are associated with MSI

•Worst prognosis.

Medullary carcinoma

•Rare.•Common in proximal colon .•Occurs in elderly.•Microscopic : Sheets of malignant cells

with vesicular nuclei , prominent nucleoli, abundant pink cytoplasm.

• Invariably associated with MSI .•Favourable prognosis .

Serrated adenocarcinoma•7.5% of all CRCs. •Common in proximal colon.•Derived from serrated adenoma.•Microscopic: ▫serrated, mucinous or trabecular pattern of

growth▫abundant eosinophilic cytoplasm▫chromatin condensation▫preserved polarity, and ▫no necrosis.

Squamous differentiation•Common in proximal colon.

•Usually associated with glandular elements (adenosquamous carcinoma)

•Occasionally , seen in a pure form (squamous cell carcinoma).

•  Evidence for human papilloma virus 16 involvement in the pathogenesis of some rectal cases .

Trophoblastic differentiation•Can occur focally in CRCs.

•hCG can be demonstrated immunohistochemically in such tumor cells.

•Occasionally the entire tumor has the appearance of a choriocarcinoma.

•This phenomenon should be distinguished from conventional adenocarcinomas( where hCG positivity is more common )

Immunohistochemical features• Conventional adenocarcinoma of large bowel express are MUC1

and MUC3.

• Mucinous carcinoma express MUC2.

• CRCs invariably positive for cytokeratin (CK) positivity for CK20 and negativity for CK7

• Positive for CEA.

• Positive for CDX2, in majority of CRCs.

• Tumor-associated glycoprotein (TAG-72) is present in 100 % of invasive colorectal carcinoma.

• CRCs , especially poorly differentiated show loss of blood group isoantigens and of HLA A, B, and C expression.

Other markers•Villin•Cathepsin B •Neurolipin-1•SRCA2 •Cadherin-17•Calretinin•Human chorionic gonadotropin (hCG)•Placental alkaline phosphatase (PLAP)

~10%•Estrogen and progesterone receptors•Racemase

Electron microscopic features

Prominent microfilamen

ts

Diagnostic modalities

CYTOLOGY BIOPSY

Biopsy

•There is a need of POSITIVE BIOPSY before radical surgery for CRC.

• In large lesions, several biopsies should be taken form diverse areas.

•Biopsy from center only granulation tissue•Biopsy from the very periphery only

hyperplastic colonic epithelium

Cytology• Its an accurate way of diagnosing CRC.

•Little practical value.

•Low-lying rectal lesions can be easily sampled.

•Brush cytology can also be performed via the fiberoptic scope.

• It is a sensitive technique, perhaps even more so than endoscopic biopsy, but it has not yet found widespread acceptance.

Various screening modalities

•Colonoscopy

•Virtual colonography

•Sigmoidoscopy

•Fecal occult blood test

•Double contrast barium enema

•Digital rectal examination

Staging and Grading

• In 1937, Dukes proposed staging for rectal carcinoma .

• In 1954, Astler and Coller proposed different staging system.

•American Joint committee on Cancer(AJCC)•The Union Internationale Countre Le Cancer

(UJCC)

Dukes’ Stage A

• The tumor involve the wall of the bowel only.

• Treatment is surgery to remove the tumor and some surrounding lymph nodes

Dukes’ Stage B• The cancer extend through

the wall has not spread to the lymph nodes.

• Colon cancer is treated with surgery and, in some cases, chemotherapy after surgery.

• Rectal cancer is treated with surgery, radiation therapy, and chemotherapy

Dukes’ Stage C• The cancer has spread to

the regional lymph nodes (lymph nodes near the colon and rectum)▫ C1: regional L.N▫ C2: mesenteric B.V.

ligature

• Colon cancersurgery and chemotherapy

• Rectalcancersurgery, radiation therapy, and chemotherapy

Dukes’ Stage D• Spread outside of the

colon or rectum to other areas of the body

• Treatment : chemotherapy.

• Surgery to remove the colon or rectal tumor may or may not be done

• Additional surgery to remove metastases may also be done in carefully selected patients

Astler and Coller Staging System

•Stage A ▫Limited to mucosa

•Stage B1▫ Involving the muscularis externa but not penetrating it

•Stage B2▫Penetrating through the muscularis externa

•Stage C1▫Confined to the bowel wall but with nodal metastasis

•Stage C2▫Penetrating through the wall and with nodal metastsis

• TNM Staging of Colon Cancer

• Tumor (T)• T0 = none evident• Tis = in situ (limited to mucosa)• T1 = invasion of lamina propria or submucosa• T2 = invasion of muscularis propria• T3 = invasion through muscularis propria into subserosa or nonperitonealized perimuscular tissue• T4 = invasion of other organs or structures

• Lymph Nodes (N)• 0 = none evident• 1 = 1 to 3 positive pericolic nodes• 2 = 4 or more positive pericolic nodes• 3 = any positive node along a named blood vessel

• Distant Metastases (M)• 0 = none evident• 1 = any distant metastasis

• 5-Year Survival Rates• T1 = 97%• T2 = 90%• T3 = 78%• T4 = 63%• Any T; N1; M0 = 66%• Any T; N2; M0 = 37%• Any T; N3; M0 = data not available• Any M1 = 4%

Microscopically, colorectal carcinoma can be graded into

▫I – well differentiated▫II- moderately differentiated ▫III- poorly differentiated

Spread and Metastasis•Common sites ▫Regional lymph nodes ▫Liver

Lymph node metastasis•More common in the tumors showing ▫poorly differentiated areas ▫highly infiltrative pattern of growth.

•Minimum number of nodes recovered from a surgical specimen of colorectal carcinoma should be 14 or 15.

Liver metastases •More common in the tumors showing

evidence of blood vessel invasion.

•Other relatively common metastatic sites include ▫peritoneum▫lung▫ovaries.

TREATMENT

•Chemotherapy•Radiotherapy•Photodynamic therapy•Radical surgery•Gene therapy

PROGNOSIS• The 5-year survival rate after curative resection

for CRC ranges between 40% and 60% .

• Local recurrence and/or regional lymph node metastases occur in over 90% of the failure cases.

•Over two-thirds of the recurrences are evident within the first 2 years and 91% by 5 years.

• The prognosis of colorectal carcinoma is related to a number of clinical and pathologic parameters.

•Category I▫Well supported by the literature, generally used in

patient management and of sufficient importance to modify TNM stage groups.

•Category IIA▫Extensively studied biologically and/or clinically.

Prognostic value for therapy, sufficient to be noted in pathology report

•Category IIB▫Well studied but not sufficiently established for

Category I or IIA•Category III▫Not yet established to meet criteria for Category I or II

•Category IV▫Studied and shows no consistent prognostic

significance

Prognosis

AgeP

SexM-P

CEA seum levels P

Tumor location +/-

Tumor multiplicity

(S) Local extent

P

Tumor size +/-

Tumor edge NP-P

Obstruction P

Perforation P Category

I

Category III

PROGNOSIS

Tumor margins/

inflm rxn G

Tumor budding

P

Vascular invasion P

Pericolonic tumor

deposits P

Perineurial invasion

P

Surgical Margins (R -

P)

Tumor thickness +/-

Microscopic tumor type (Mu/S/A -P,

Me -G)

Acinar morphology P

Presence of neuroendocrine cells +/-

Category IIA

Category IIA

Category IIB

III

PROGNOSIS

Tumor angiogenesis

P

Mucin related antigens P

Fascin P

HLA-DR expression

G

pRB and P16P

hCG expression

+/-

BCL2 protein expression G

DNA ploidy +/-

Cell proliferation

+/-

Claudin-1Loss- P

III

IIB

PROGNOSIS

Loss of chr 18q

P

TGF-B1 mutations

G

Oncogene & TSG

expression P53 –PMSI-G

LN involveme

ntP

Pattern of LN rxnCMI- G

Staging

Microscopic grade

Category I

Category IIACategory IIB

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