**2. History**

Endoscopy in its modern form began in 1806 with the invention of the Lichleiter, or 'light conductor', by Philipp Bozzini. This device consisted of two parts: the light container and viewing device, and the mechanical part (various speculae) that facilitated access to the subject's body. The fibre-optic endoscope was originally invented by the then medical student, Heinrich Lamm in 1930 [1]. Poor image quality limited the utility of this endoscope until scientific advances made by Harold Hopkins and Narinder Singh Kapany in 1954 [2] were adapted by Dr. Basil Hirschowitz to create the flexible fiberscope [3].

**3.1. Tumour markers**

*3.2.1. Transabdominal ultrasound (US)*

*3.2.2. Computed tomography (CT)*

**3.3. Percutaneous biopsy**

**3.4. EUS-guided biopsy**

**3.2. Imaging**

CA19-9 is a useful biomarker for monitoring response to treatment, or disease progression or recurrence in patients with an established histological diagnosis of PC [8]. However, the specificity of CA19-9 (68–92%) and positive-predictive value (0.9% for serum concentrations

Endoscopic Ultrasound in Pancreatic Cancer http://dx.doi.org/10.5772/intechopen.75211 75

US can be used to assess pancreatic masses ≥3 cm in size with up to 95% sensitivity [10]. Specificity of US is reported between 94 and 98%, however sensitivity decreases substantially when assessing smaller lesions, and is highly operator-dependent [11]. In order to improve detection of PCs at a size where curative resection is achievable, more sensitive investigations are necessary.

Abdominal CT scan (multidetector CT, MDCT) has a sensitivity nearing 100% for pancreatic lesions >2 cm, which reduces to 77% for tumours ≤2 cm [12]. Its utility in assessing local extension is demonstrated by an accuracy for predicting surgical resectability of 80–90% [13], however is limited by its ability to detect liver metastases and early lymph node metastases [11].

Percutaneous, image-guided pancreatic mass biopsies using ultrasound or CT, are safe and effective at obtaining the diagnosis of PC. Due to the direct sampling nature of the procedure, specificity is close to 100%, with varying sensitivity between 80 and 90% [14]. Theoretic concerns with regards to percutaneous biopsies include the risk of tumour seeding along the biopsy tract, or the increased risk of peritoneal carcinomatosis in patients having undergone

EUS-guided fine-needle aspiration (EUS-FNA) uses the instrument channel of the endoscopy to pass a biopsy needle in front of the linear-array ultrasound probe to obtain tissue from lesions under direct ultrasound visualisation. The angle of the needle can be modified to target more cellular-appearing aspects of the target lesion. Two to 10 passes are made into the lesion with the needle and the use of an on-site cytopathologist, or specialist nurse trained in assessment of samples for cellularity is recommended. EUS-FNA allows for tissue acquisition for diagnostic purposes with a low rate of morbidity and mortality, and allows for early

Eloubeidi et al. conducted a review of 100 patients who underwent EUS-FNA, and found 95% sensitivity, 95% specificity, 100% positive predictive value, and 85.2% negative predictive value [17]. These results have been replicated and shown to hold in multiple studies, including

percutaneous biopsy, and is contraindicated in potentially-resectable cases [15].

genetic and molecular analysis for research and therapeutic decisions [16].

>37 units/mL) negates the utility of CA19-9 in the diagnosis of PC [9].

Ultrasound as an investigational modality was also being developed at this time, with Neurologist Dr. Karl Dussik publishing the first use of diagnostic ultrasound in 1941 [4]. The addition of radial ultrasound technology to endoscopy is credited to Dr. DiMagno in 1980, who felt that by internalising the ultrasound probe, problems with interfering gas patterns and nearby organs could be avoided, and the accuracy of ultrasound would be improved [4]. Although the intent at the time was to use this technique to image the pancreas, the coupling of endoscopy and ultrasonography also led to the development of transoesophageal echocardiography, endoscopic bronchial ultrasound, and trans-rectal ultrasound.

In 1991, Dr. Peter Vilmann and Søren Hancke utilised the curved linear array endoscope to facilitate minimally-invasive diagnostic and therapeutic interventions during endoscopic ultrasound [5]. The use of the linear array ultrasound probe enabled the use of instrument channels. These channels have facilitated the current utility of endoscopic ultrasound to perform fine needle aspirations (EUS-FNA) for diagnostic purposes, and for minimally-invasive therapeutic alternatives to radiologically-guided, or surgical drainage of collections, for biliary drainage (EUS-BD), and to perform celiac plexus neurolysis (EUS-CPN) [6, 7].
