Colon carcinoma is identified as the most frequent malignancy of the gastrointestinal tract. The clinical presentation, comprised of abdominal pain, nausea, vomiting, anemia and weight loss is frequently insidious, thus the diagnosis is delayed in the majority of patients. Both noninvasive and invasive imaging studies, as well as biopsy with the histopathological examination, are used to define the clinical stage and prognosis.
With almost 100,000 new cases estimated to occur in the United States in 2017 (with equal gender predilection), colon carcinoma is among the most commonly diagnosed malignant diseases in the Western World [1] [2]. The incidence rate seems to be highest among the elderly individuals (between 60-70 years of age), and several risk factors have been established, most important being physical inactivity, obesity and increased body weight, cigarette smoking, overt alcohol consumption and certain dietary habits, such as excessive intake of animal fats and reduced fiber in nutrition [3] [4] [5]. Countries belonging to the developed world (Canada, Denmark, Sweden, the United States, and several other) report the highest prevalence rates [3] [4] [5] The clinical presentation of colon carcinoma is usually nonspecific and up to several months may pass before the diagnosis is even suspected [6] [7]. One of the reasons is the insidious and nonspecific onset of gastrointestinal complaints such as abdominal pain, fatigue, weakness, and changes in bowel habits (both constipation and diarrhea) [4] [5] [8]. This is typical for right-sided colonic cancers, whereas left-sided carcinomas of the colon more frequently produce symptoms that are highly suggestive of a neoplastic process in the large intestine - rectal bleeding and anemia [4] [9]. In addition, cramping, anorexia, and abdominal discomfort may be reported [4] [8]. As anemia becomes more severe and clearly stems from iron depletion due to continuous bleeding, cardiac manifestations (angina pectoris and palpitations) can appear, in which case immediate suspicion toward colon carcinoma, especially in elderly men and women, should be mounted [4] [5].
Early recognition of colon carcinoma is favored, especially if we know that 5-year survival rates range between 40%-60%, depending on the stage [1] [6] [7] [8]. In fact, the degree of tumor invasion and infiltration of adjacent lymph nodes or distant organs are the two predictors of mortality in this patient population, suggesting that advanced stages of the disease carry a poorer prognosis undoubtedly [4]. In all patients with non-specific gastrointestinal (GI) complaints, a thoroughly obtained patient history and a meticulous physical examination can provide sufficient clues to investigate colon carcinoma as a potential cause, especially among the elderly. A complete blood count (CBC) and basic biochemical workup will often identify sideropenic anemia, in which case a fecal occult blood test must be performed. If the test is positive, imaging studies should be employed. Several studies have been listed in the literature as possible modalities for visualization of the tumor, including barium enema and computed tomographic colonography (CTC), but optical colonoscopy (OC) remains the cornerstone in diagnosing colon carcinoma [1] [10]. Moreover, fluorodeoxyglucose positron emission tomography (FDG-PET), magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI), ultrasonography, computed tomography (CT) as well as contrast-enhanced MRI have also been mentioned as valuable procedures in determining the stage of the tumor [1] [4]. A definite diagnosis, however, is made after a biopsy sample is obtained during colonoscopy for microscopic evaluation, and the tumor is classified according to the degree of local (but also distant) tissue invasion by the TNM classification [4] [5]: