Spindle Cell Tumours of the Gastro-Intestinal Tract

Geraint T Williams

Pathology Department

Wales College of Medicine

Cardiff University

GI Spindle Cell Tumours early 1990s

• Leiomyomas

• Epithelioid leiomyomas

• Leiomyosarcomas

• Neurofibromas

• Schwannomas

• Malignant Schwannomas

Immunostaining early 1990s

•Desmin

•Smooth muscle actin

•Smooth muscle myosin

•S-100 protein

•Neurofilament

•PGP9.5

GI Spindle Cell Tumours mid 1990s

Many tumours with equivocal immunostaining:• GISTs• GANTs• STUMPs• SITSFs• OSTs, GaSTs, DuSTs, JeSTs, ISTs, CoSTs,

ReSTs, ASTs

Gastrointestinal Stromal Tumours 2000s

Immunopositivity

for:

• c-kit (KIT, CD117)

• CD34

• bcl-2

• nestin

• protein kinase C-theta

Leiomyoma• Oesophagus, stomach, small bowel • Usually <0.5 cm, polypoid and asymptomatic• Most related to muscularis mucosae• Oesophageal leiomyomas in MEN1

– LOH at 11q13

• Microleiomyomas at oesophago-gastric junction in 8% population

• Diffuse oesophageal leiomyomatosis– associated with Alports-type nephropathy

• Peritoneal leiomyomatosis

Leiomyosarcoma

• Very rare

• Oesophagus, stomach, small bowel

• Expresses desmin and/or smooth muscle actin

• Usually high grade (>10 mitoses/10 HPFs)

Ganglioneuromatosis

Diffuse submucosal and myenteric:

May cause motility disorders/megacolon

NF-1

Multiple endocrine neoplasia IIb

Shekitka et al 1994 Am J Surg Pathol 18: 250-7

Smith et al 1999; Gut 45: 143-6

Ganglioneuromatosis

Diffuse submucosal and myenteric:

May cause motility disorders/megacolon

NF-1

Multiple endocrine neoplasia IIb

Polypoid mucosal:

Juvenile polyposis

Cowden’s syndrome

Gastrointestinal “Schwannoma”

• Benign

• Not associated with NF-1

• No NF2 lesions

• Majority gastric, occasionally oesophageal or colonic, virtually never in small bowel

• Intramural or polypoid

• No necrosis, haemorrhage or cystic change

Sarlomo-Rikala & Miettinen 1995 Histopathology 27: 355–60Hou et al 2005 Histopathology in press

Gastrointestinal “Schwannoma”

•Typically brisk lymphoid reaction, usually as a peritumoural lymphoid cuff, often with germinal centres

•Mainly spindle, rarely epithelioid

•Verocay bodies unusual

•Significant nuclear atypia but mitoses very sparse

Gastrointestinal “Schwannoma”

•S-100 positive

•GFAP and nestin usually positive

•Occasional CD34 positive cell

•KIT, SMA, CK, NF, desmin negative

Mucosal epithelioid nerve sheath tumours

• Small polyps

• Epithelioid cells in nests and whorls

• Intranuclear pseudoinclusions

• S-100 positive

• KIT negative

Lewin et al 2005 Am J Surg Pathol 29: 1310

Benign fibroblastic polyps of the colon

• Solitary

• Bland monotonous mucosal spindle cell proliferation

• Vimentin positive only

Eslami-Varzanehet al 2004 Am J Surg Pathol 28: 374

Gastrointestinal Stromal TumoursImmunopositivity for:• vimentin 95-100%• nestin 90-100%• CD34 70-85% (low in SI)• smooth muscle actin 20-40% (high in SI)• heavy caldesmon 60-80%• connexin 43 most SI, rare in stomach• desmin 5-20%• S-100 0-15% (mainly SI)• cytokeratin rare

KIT (CD117)

• Receptor for Stem cell factor • Trans-membrane tyrosine kinase growth factor

receptor• Expressed on

– Haemopoietic stem cells– Mast cells– Melanocytes– Breast epithelium– Interstitial cells of Cajal (pacemaker cells)

Interstitial cells of Cajal

• Gut pacemaker cells

• Form intramural network

• Develop from intrinsic gut mesenchyme

• Common precursor with smooth muscle cells

• Express KIT and nestin

Interstitial cells of Cajal

• Similar cells now described in– Pancreas

– Portal vein

– Fallopian tube

– Myometrium

– Breast

KIT Mutations in GISTs

• Activating mutations exon 11, occasionally in exon 9

• ~ 85% of GISTs

• More frequent in malignant GISTs

• Different mutations (exon 17) in mast cell tumours

Hirota et al 1998 Science 279:577

KIT mutations in GISTs

• “Early” event in tumorigenesis

• Transfection into cell lines leads to transformation by– autophosphorylation of KIT– ligand-independent tyrosine kinase activity– cell proliferation

Hirota et al 1998 Science 279:577

Rubin et al 2001 Cancer Res 61:8118

KIT Mutations in GISTs

• Present in 72%

– 80% exon 11

– 17% exon 9

• Exon 9 more frequent in aggressive small bowel GISTs

• Exon 11 nearly all spindle cell

Penzel et al 2005 J Clin Pathol 58:634

Familial GISTs

• Germline mutations of KIT • Multiple tumours• Cutaneous hyperpigmentation• Hyperplasia of Cajal cells• GI Motility disorders• Some overlap with NF-1

Hirota et al 1998 Nat Genet 19: 323Chompret et al 2004 Gastroenterology 126: 318

Chromosomal abnormalities in GISTs

• Most tumours:– 14q, 22q deletion

• Malignant tumours:– 1p, 9p deletion– 8q and 17q amplification

Gastrointestinal Stromal Tumours (GISTs)

• Incidence 14.5/million/year (prevalence 129/million)

• 5th-7th decade• Decreasing frequency down GI tract• Pedunculated, dumb-bell or ulcerated• May arise in mesentery, omentum, retroperitoneum• Prediction of behaviour unreliable • Predisposition:

– Familial – Neurofibromatosis– Carney’s triad

Nilsson et al 2005 Cancer 103:821

GISTs in NF-1• Multiple tumours• Mainly in small intestine• Spindle cell, low grade• Often skeinoid fibres• Often S-100 positive• KIT and PDGFRA mutations uncommon• Background Cajal cell hyperplasia

Andersson J et al 2005 Am J Surg Pathol 29: 1170-6 Takazawa et al 2005 Am J Surg Pathol 29: 755-63

Carney Syndromes

Carney J AThe triad of gastric epithelioid leiomyosarcoma, pulmonary chondroma and functioning extra-adrenal paraganglioma: a 5-year review. Medicine 1983; 62: 159–169

Carney J A, Stratakis C A Familial paraganglioma and gastric stromal sarcoma: a new syndrome distinct from the Carney triad. Am J Med Genet 2002; 108: 132-139

Gastrointestinal Stromal Tumours (GISTs)

• Small tumours found incidentally

• Symptomatic– Obstruction

– Bleeding

Malignant GISTs

• Approximately 30-45%

• Notoriously difficult to predict

• Intra-abdominal spread, especially multinodular peritoneal seeding

• Distant metastases:– Liver

– Lung

– Bone

GISTs - Outcome

• Resectable– 10 year survival 30-50%

• Unresectable, metastatic– median survival 12 months

– no response to conventional chemotherapy

Predictors of Malignant Behaviour in GISTs

• Uncertain malignant potential

• Low malignant potential

• High malignant potential

Major Predictors of Malignant Behaviour in GISTs

• Size (>5 cm)

• Mitotic counts (>5/50 HPF)

Risk of Aggressive Behaviour (NIH)

Size Mitotic Count

Very low risk <2 cm <5/50 HPF

Low risk 2-5 cm <5/50 HPF

Intermediate risk <5 cm5-10 cm

6-10/50 HPF<5/50 HPF

High risk >5 cm>10 cmAny size

>5/50 HPFAny rate

>10/50 HPF

Fletcher et al 2002 Hum Pathol 33: 459-465

Behaviour of GISTs

Frequency Tumour- Median related deaths survival

(months)

Low malignant potential 56% 1%

High malignant potential 29% 63% 40

Overtly malignant 15% 83% 16

Nilsson et al 2005 Cancer 103:821

Other Predictors of Malignant Behaviour in GISTs

• Site (stomach vs intestine)

Gastric GISTsSize Mitotic Count

Benign <2 cm <5/50 HPF

Probably benign 2-10 cm <5/50 HPF

Uncertain or lowmalignant potential

<2cm >5/50 HPF

Low to moderatemalignant potential

2-5 cm>10 cm

>5/50 HPF<5/50 HPF

High malignantpotential

>5 cm >5/50 HPF

Miettinen et al 2005 Am J Surg Pathol 29: 52-68

Other Predictors of Malignant Behaviour in GISTs

• Site (stomach vs intestine)

• Histological type (epithelioid>spindle)

• Cellularity and pleomorphism

• Invasive pattern

Other Predictors of Malignant Behaviour in GISTs

• Chromosome 9q deletion

• 1530ins6 mutation of KIT (intestine)

• P16 loss

• P53 positivity (gastric GISTs)

Lasota et al 2003 Hum Pathol 34: 1306Gunawan et al 2004 J Pathol 202:421Feakins 2005 Histopathology 46: 270

Schneider-Stock et al 2005 Clin Cancer Res 11: 638

Gastrointestinal Stromal Tumours (GISTs)

• Spindle cell

• Epithelioid

• Round cell

• Clear cell

• Plasmacytoid

• Pleomorphic

Differential Diagnosis

Inflammatory fibroid polyp

Inflammatory myofibroblastic tumour

Solitary fibrous tumour

Mesenteric fibromatosis

Dedifferentiated liposarcoma

Inflammatory Fibroid Polyp

Stomach, ileum, proximal colon

Usually presents with intussusception

Centred on submucosa

Distinctive histology:Thin-walled blood vessels

Onion-skin arrangement of palisaded spindle cells around larger blood vessels

Oedema

Eosinophils

Inflammatory Fibroid Polyp

CD34 positive

fascin positive

bcl-2 negative

KIT negative

CD99 negative

Pantanowitz et al 2004 Am J Surg Pathol 28: 107

Inflammatory Myofibroblastic Tumour

•Loose mixture of fibroblasts, myofibroblasts and inflammatory cells

•May be ganglion-like cells

•CD34 negative

•ALK-1 positive

•May be KIT positive

•? tumour of fibroblastic reticulum cells

Nonaka et al 2005 Histopathology 46: 604

Solitary Fibrous Tumour

Wide spectrum histologicallyFascicular or storiform patternEctatic vesselsCD34 positiveBcl-2 positiveKIT negativeCD99 positive

Mesenteric Fibromatosis

May be KIT positive (depending on antibody)

beta-catenin positive (nuclear)

CD34 negative

Montgomery al 2002 Am J Surg Pathol 26: 1296

Dedifferentiated Liposarcoma

mdm2 positive

cdk4 positive

S-100 positive

may be KIT positive

Differential Diagnosis

Kaposi’s sarcoma

KIT negative

Angiosarcoma

CD31 positive

Occasionally KIT positive

Mesothelioma

Rare weak positivity for KIT

Differential DiagnosisSarcomatoid carcinoma / carcinosarcoma

Rarely KIT positive(GISTs may show perinuclear dot staining for CAM5.2)

Small cell carcinomaMetastases:

melanomaseminomamyeloproliferative lesions, mast cell tumoursbreast, ovarian, nasopharyngeal, colorectal carcinoma

Problems with KIT immunostaining

• Different antibodies with different sensitivity and specificity (e.g. mesenteric fibromatosis)

• Pre-treatment affects staining• Expensive• Level of expression variable• Granular cytoplasmic staining alone unreliable

– Membranous and/or paranuclear dot reliable

• Use normal stomach as control– watch for aberrant expression in smooth muscle

KIT-negative GISTs

• Epithelioid morphology commoner

• Usually CD34 and Protein kinase C-theta positive

• Usually have 14q and 22q deletions– (and 1p deletions in malignant tumours)

Debiec-Rychter et al 2004 J Pathol 202:430

KIT-negative GISTs

• ~30% have activating mutations of Platelet derived growth factor receptor-alpha (PDGFRA, tyrosine kinase)

• Exon 18, occasionally in exon 12

• KIT and PDGFRA mutations mutually exclusive

Heinrich et al 2003 Science 299:708

Debiec-Rychter et al 2004 J Pathol 202:430

Medeiros et al 2004 Am J Surg Pathol 28: 889

PDGFRA mutation in GISTs

• Autophosphorylation and ligand-independent activation of tyrosine kinase receptor

Heinrich et al 2003 Science 299:708

PDGFRA mutant, KIT-negative GISTs

• Mainly gastric

• Mainly epithelioid

• Tumour giant cells

• Usually low mitotic rate

• 83% benign behaving

Lasota et al 2004 Lab Invest 84:874

Pauls et al 2005 Histopathology 46:166

Penzel et al 2005 J Clin Pathol 58:634

PDGFRA immunostaining

• 8/125 GISTs (all 8 KIT-negative)

• 4/15 intra-abdominal desmoids

• 0/12 leiomyomas

• 0/8 leiomyosarcomas

• 0/3 schwannomas

• 0/2 solitary fibrous tumours

• 0/1 inflammatory fibroid polyp

• 0/1 inflammatory myofibroblastic tumour

Rossi et al 2005 Histopathology 46:522

DOG-1

• “Discovered on GIST-1”

• Identified through gene expression profiling

• Expressed in 136/139 GISTs irrespective of KIT or PDGFRA mutation status

• 0/17 fibromatosis

• 0/3 schwannomas

• 4/438 non-GISTs – synovial sarcoma, leiomyosaroma, fibrosarcoma, Ewings sarcoma/PNET

West et al 2004 Am J Pathol 165:107

Imatinib (ST1571; Glivec)

• Tyrosine kinase inhibitor developed as inhibitor of PDGF receptor

• Powerful inhibitor of ABL tyrosine kinases– Effective treatment for chronic myeloid leukaemia (ABL

and BCR-ABL)

• Dramatic response of malignant GIST with relatively mild toxicity

Joenssu et al 2001 NEJM 344:1052

Imatinib (ST1571; Glivec)

• EORTC Phase I study in advanced cases showed – inhibition of tumour growth in 32/36 cases – >50% volume reduction in 19 patients– side effects (nausea, vomiting, oedema, rash) limited

treatment in 5 patients– response seen within 2 months

• Similar findings in US Study of 36 patients

van Oosterom et al 2001 Lancet 358:1421

Imatinib (ST1571; Glivec)

• Phase III study:– 946 patients– 5% complete response– 47% partial response– 32% stable– median time to best response 107 days– 73% free from progression at 12 months– serious side effects 37%

Verweij J et al 2004 Lancet 364: 1127

Imatinib (ST1571; Glivec)

• Complete response very unusual• Partial response rates

– 85 Exon 11 KIT mutations 83.5%– 23 Exon 9 KIT mutations 47.8%

• “Escape” with time in some cases– associated with novel KIT mutations (exon 17)

Heinrich et al 2003 J Clin Oncol 21: 4342Chen et al 2004 Cancer Res 64: 5913

Antonescu et al 2005 Clin Cancer Res 11: 4182

NICE proposals - Imatinib

• 400mg/day for KIT-positive unresectable or metastatic disease

• Continue only if response is achieved within 12 weeks

Response to Imatinib

• South West Oncology Group

• Assessed by CT, MRI or PET– Complete response– Partial response– Stable disease– Progressive disease– Unknown

NICE proposals - Imatinib

• 400mg/day for KIT-positive unresectable of metastatic disease

• Continue only if response is achieved within 12 weeks

• For responders continue until development of progressive disease

• Increased dose not recommended in non-responders• £19,000 per year

CSTI571-B2222

• Phase II, 147 patients, 91% KIT +ve• Unresectable or metastatic GIST• 400mg or 600mg/day for median 21 months• Survival 88% at 1 year 78% at 2 years• No CR, 66% PR, 17% stable, 12% progressive• Improved performance status• 15% major adverse events, 10% withdrew• Resistance in 16 pts, 3 primary, 13 secondary

(SU11248)

• Multi-targeted tyrosine kinase inhibitor • Objective response or stable disease in 26/48

progressing tumours on imatinib• Particular benefit in exon 9 mutants

Demetri et al 2004 ASCO Abstract 3001

Imatinib-treated GISTs

• Myxoid, gelatinous consistency; cystic change• Decreased cellularity• Stromal hyalinisation• More epithelioid• Loss of KIT and/or CD34 immunoreactivity• Acquired desmin immunoreactivity• Novel KIT mutations especially exon 17

Antonescu et al 2005 Clin Cancer Res 11: 4182Loughrey et al 2005 J Clin Pathol 58: 779

Pauwels et al 2005 Histopathology 47: 41

Conclusions

• Diagnosis of GI spindle cell tumours, and GIST in particular, is important

• Should be made by experienced pathologists with access to quality-assured KIT immunostaining

• Molecular diagnosis likely to become important• Managed by MDT• Surgery is first line therapy• Imatinib should be considered for patients with advanced or

unresectable tumours• Participate in trials