Pathology Flashcards
Describe this

- 2x2cm nodular lesion
- Raised
- Rolled edge
- Central ulcerated crater
- Visible telangiectasia
- Shiny surface
- Clinical features suggestive of basal cell carcinoma
What is basal cell carcinoma?
- Malignant proliferation of basal cells of epidermis
- Most common skin cancer (80%)
- M > W
- Sun exposed areas (head and neck)
- Locally invasive and rarely metastasise
- Subtypes: Nodular (most common), superficial, morphoeic (scar like with indistinct borders), basosquamous
Why is there erythema associated with BCC
- Telangictasia: dilated blood vessels in epidermis (directly due to BCC or as a result of sun damage)
- Local inflammatory response?
Histological classification BCC
- Localised: nodular, nodulocystic, pigmented
- Superficial: superficial spreading
- Infiltrative: morphoeic
DDX BCC
- NODULAR: SCC, skin appendage tumour, dermatofibroma
- PIGMENTED: Melanoma, compound naevus
- MORPHEAFORM: Scar, trichoepithlioma
- SUPERFICIAL: psoriasis, eczema, Bowen’s disease
How does BCC spread
- Rarely metastasises
- Locally invasive
How can you ensure complete intra-operative resection for BCC?
- Moh’s micrographic surgery
- Sequential horizontal excision with immediate intra-operative frozen section examination
- Resection until adequate margins
BCC risk factors
- Congenital: Fitzpatrick skin type I, Xeroderma pigmentosum (AR, XPA gene)
- Acquired: UV exposusure, age
BCC management
- Conservative: sun protection
- Medical: 5-FU cream, imiquimod cream (activation of TLRs = local immune response), photodynamic therapy, cryotherapy
- Surgical: Excision, Moh’s micrographic surgery
Excision margins BCC
- Primary <2cm: 5mm
- Primary >2cm or morphoeic: 10-15mm
- Recurrent: 5-10mm
Define metastasis
- Process by which a primary malignant neoplasm gives rise to secondary tumours at distant sites through lymphatic, haematogenous or transoleomic (penetrating visceral surface e.g. peritoneal) spread
Management of MRSA colonisation?
- Isolation side room
- Contact precautions
- Nasal mucopuricin 2%
- Chlorhexidine 4% daily body wash (hibiscrub)
- Rescreen after 5 days
What is PVL staph?
- Panton valentine leucocidin
- Exotoxin comprising two subunits
- Forms pores in membrane of leucocytes cell lysis and death by necrosis
What other staph aureus toxins are there?
- TSST-1 > Binds MHC-II with high affinity cytokine storm toxic shock syndrome
- Haemolysin
- Exfoliatin
- Enterotoxin
What is rheumatic fever?
- Systemic complications of pharyngitis due to group A beta-haemolytic strep
- T2HSR caused by molecular mimicry
- Bacterial M protein resembles protein found in normal tissues
How does acute rheumatic fever lead to chronic rheumatic heart disease?
- Repeat attacks of ARF lead to valve scarring
- Thickening of valve leaflets and cordae tindinae
- Fusion of valve commissures
- Increased risk of infective endocarditis: Strep Viridans (previously damaged valve)
How can you diagnose acute rhematic fever?
- JONES criteria
- Joint pain (migratory polyarthritis)
- Pancarditis (endocarditis most commonly affects MV, myocarditis (aschoff bodies and anitschkow cells), pericarditis)
- Nodules
- Erythema marginatum
- Sydneham’s chorea (TS2HR affecting basal ganglia)
- + positive ASOT titre
- Minor criteria: Fever, elevated ESR
What is a GIST?
Histopathology report below:
- Large, well circumscribed. Fleshy, tan pink lesion in the muscularis propria of the stomach.
- Ulceration
- CD 117
- Nodal involvement
- No metastasis
- MC mesenchymal cell of the GIT
- Arises from interstitial cells of Cajal in myenteric plexus of muscularis propria (pacemakers cells of GIT for peristalsis and segmentation)
- Stomach (80%) > jejunum/ileum > duodenum > colorectal
- Most form due to activating mutations in proto-oncogene KIT
- Positive stains: CD117 (tyrosine kinase growth factor receptor for KIT)
Difference between GIST and gastric adenocarcinoma
- GIST = Mesenchymal cell tumour from interstial cells of cajal
- Gastric adenocarcinoma due to malignant proliferation of surface epithelial cells
- Intestinal type: MC, associated with H. Pylori and nitrosamines. Large ulcer with heaped margins
- Diffuse type: signet ring cells with diffuse infiltration and thickening of stomach wall (linitis plastica).
How do GISTs behave?
- Peritoneal spread with liver metastasis
- Rarely metastasise via lymphatics
- Size and mitotic rate predictive of behaviour
Management GIST
- Surgical resection
- Chemotherapy: imatinib (tyrosine kinase inhibitor)
What is jaundice?
- Yellow discolouration of skin, sclera and mucous membranes
- Serum bilirubin binds to elastin
- Pre-, intra- and post-hepatic causes
Patient develops ascites, how would you investigate?
- Broadly: transudative (<30g protein /L) and exudative (>30g protein/L) causes of ascites
- Full Hx and examination
- Bloods: LFTs (hepatocellular damage), clotting/INR (impaired synthetic function), FB, UE, CRP
- USS: Confirm presence of ascites, examine for portal HTN (splenomegaly, collaterals)
- Paracentesis: Chemistry (SAAG, tryglycerides, amylase), microscopy and culture (PMN >250 = SBP, gram stain), cytology
- Cross-sectional imaging
Definition of a polyp
- Raised protrusions of colonic mucosa
Types of colonic polyp?
-
Adenomatous polyps arise due to neoplastic proliferation of glands. Benign but may progress through adenoma-carcinoma sequence
- Subclassified on growth pattern:
- Tubular
- Tubulovillous
- Villous (highest rate of malignant transformation)
- Subclassified on growth pattern:
- Hyperplastic arise due to hyperplasia of glands
- Inflammatory pseudopolyps (not protrusions of colonic mucosa, inflammatory debris)
- Hamartomatous: disordered growth of tissue native to site of origin. A/W PJS
Hyperplasia vs dysplasia?
- Hyperplasia = increase in cell number
- Dysplasia = disordered cellular growth. May arise due to longstanding hyperplasia
22M multiple polyps all throughout colon
DDX?
- FAP
- Gardner’s syndrome
- Turcot’s syndrome
- Peutz Jegher
- IBD with pseudo polyps
- C. diff
Treatment FAP
- Genetic counselling
- Surveillance colonoscopy
- Colectomy with IRA
- Colectomy with J-pouch formation
- Panproctocolectomy + ileostomy
What is FAP?
Familial adenomatous polyposis
- Autosomal dominant
- APC gene mutation chromosome 5
- APC = Tumour suppressor gene
What is HNPCC?
Hereditary non-polyposis colorectal carcinoma
Lynch syndrome
- Autosomal dominant
- Mutations in genes that are involved in mismatch repair
- MLH1 and MSH2
- Amsterdam criteria: 3 family members with CRC, 2 generations, 1 <50
Peutz Jegher Syndrome
- Autosomal dominant
- Hamartomatous polyps through GI tract
- Oromucosal hyperpigmentation
- STK11 gene
Extra-intestinal features of FAP
- Gardner’s syndrome: fibromatosis and osteomas
- Turcot’s syndrome: glial tumours and medulloblastoma
What is APC
- TSG
- Chromosome 5
- Mutated in FAP
What is KRAS
- Proto-oncogene
- Chr 12
- RAS/MAPK pathway
- Mutation = oncogene = uninhibited cell growth
- Secretes growth factors that permit anchorage independence > adenoma formation
What is P53
- Tumour suppressor gene
- Chr 17
- Regulates progression through G1/S
- Upregulates DNA repair enzymes, if not possible then induces apoptosis
- Knudson two hit hypothesis > both copies have to be mutated
Modified Duke’s
- A: Confined to mucosa (90%)
- B1: Extends to muscularis propria (80%)
- B2: Extends through muscularis propria, no nodes (70%)
- C1: Not through muscularis propria, nodes involved (30%)
- C2: Extends through muscularis propria, nodes involved
- D: Distant metastasis (<10%)

TNM colorectal
- T1: Mucosa
- T2: Muscularis propria
- T3: Through muscularis to serosa
- T4A: Full thickness
- T4B: Grown into nearby organs
- N0: No nodes
- N1: <3
- N2: >3
- M0
- M1
Adenoma-carcinoma sequence FAP
Mutated FAP > Hyperplasia > KRAS mutation > Dysplasia > loss of P53 > Adenocarcinoma
What is a carcinoid tumour?
- Neuroendocrine tumour that arises from AUPD cells (cells which share common function in producing low molecular weight polypeptide hormones)
- MC tumour of appendix
- 20% of GI carcinoids found in appendix (appendix > ileum > rectum)
- Also found in lung, ovaries, testes
Management of carcinoid tumour?
- Medical: octreotide (somatostatin analogue to reduce serotonin) and antihistamines
- <2cm: Appendicectomy is curative
- >2cm or involving base: Right hemicolectomy
What is carcinoid syndrome?
- Collection of clinical features seen following metastasis of carcinoid tumours to the liver
- Occur due to overproduction of serotonin, histamine and secretin
- Flushing and diarrhoea
- Bronchospasm
- Pulmonary stenosis and TR
- 10% of patients with carcinoid tumours
Investigations of carcinoid syndrome
- 24h urinary 5-HIAA (serotonin metabolite)
- Octreoscan: PET with radiolabelled octreotide (somatostatin analogue) binds NETs.
- CT/MRI
Describe this

- Endoscopic image
- Hyperaemic mucosa
- Numerous yellow-white mucosal plaques throughout
- Pseudomembranous colitis
What is c. diff?
Clostridium dificille
- Gram positive spore forming rod
- Facultative anaerobe
Pathophysiology of pseudomembranous colitis?
- Broad spectrum antibiotics (clindamycin) eradicate microbial flora favouring growth of c. diff
- C. diff toxin A = enterotoxin, c. diff toxin B = cytotoxin
- Pseudomembrane = mucopurulent exudate from crypts
- necrosis
- Adherent layers of inflammatory cells and cellular debris at site of colonic mucousal injury
- Excess fibrin deposition
How does C. diff spread?
- Spore forming bacteria
- Metabolically dormant form of bacteria, resistant to environmental stressors (extremes of temperature, ethanol, pH)
- C. diff cannot cause disease unless spores germinate into metabolically active toxin producing cells (germination)
- Spores spread through nosocomial infection
Management of c. diff?
- Isolation room
- Contact precautions (apron and gloves)
- Cessation of causative ABx if appropriate
- PO Vancomycin 125mg QDS/ Fidaxomicin/ Metronidazole
- Tigecycline/ IVIG if no response
- Faecal transplantation in recurrent episodes
What is toxic megacolon?
- Colitis with colonic dilation >6cm
- IBD, infectious colitis (c. diff)
Management of toxic megacolon?
- Resuscitation
- ABX/steroids
- NG decompression
- Laparotomy + subtotal colectomy with end ileostomy formation