ABSTRACT
Melanosis coli is an incidental benign finding characterized by the deposition of dark brown pigment in the colonic mucosa. The cause of this situation is due to long-term laxative use. We report a female patient who underwent surgery for colon adenocarcinoma and diagnosed as melanosis coli during histopathological examination.
Introduction
Melanosis coli is characterized by increased macrophages localized in the colonic mucosa, with black-brown pigment in their cytoplasm. It is asymptomatic and is often incidentally detected during colonoscopic or histopathological examination.1 Histochemically, the intracellular pigment cross-reacts with Fontana-Masson and is lipofuscin-like. Ultrastructural studies have shown that this pigment is formed by the destruction of apoptotic colonic epithelial cells.2 Melanosis coli is detected during the investigation of the causes of constipation due to malnutrition especially in the elderly. Recently, the incidence has increased as a result of colonoscopic examinations.1,3
Discussion
Although there is no clear information about the incidence of melanosis coli, rates ranging from 1-59.5% have been reported.4,5 It is more common in women as in our case and in older age.1,6 Pigment can be observed more intensively in the cecum and ascending colon than in the distal column.1,2 In our case, melanosis coli was detected in the sigmoid colon. The use of laxatives, especially laxatives containing anthraquinone, is a well-known cause for melanosis coli. It can usually develop after 4-9 months of use. With the discontinuation of use, it may recede within months.7 It can be seen in varying rates in inflammatory bowel disease, colonic diverticulum, chronic diarrhea, non-steroidal anti-inflammatory drug use, colorectal polyps and tumors.5,8 It has been reported in the literature that it is frequently associated with colonic polyps.5,9 In one study, it was emphasized that pigment-free polyps were more easily detected in endoscopic examination because of the black-brown color of the mucosa.5 These polyps may include adenomatous polyps, which may include carcinoma focus. Biopsy from the non-pigmented areas in the recognition and exclusion of these lesions is also among the recommendations.10 In a study that reported the association with non-neoplastic polyps that contain pigment, the toxic effect resulting in the destruction of the apoptotic colonic epithelial cells was claimed to cause the development of the colorectal polyps, as well as melanosis coli.8 Although no polyp was detected in our case, it was observed that there was no macroscopic and microscopic pigment accumulation in ulcerated tumor tissue in accordance with the literature. Diffuse black-brown pigment was observed on the mucosa and serosal surface of the tumor proximal. Melanosis coli is a benign and reversible lesion. However, the findings in the studies on whether there is a relationship between colorectal tumors seen in similar age groups are controversial. In some of the studies, an increased risk for the tumor was reported in cases with melanosis coli, while some did not suggest a relationship.6,9 In conclusion, as in our case, melanosis coli can be defined as a lesion that may arise as a result of long-term laxative use in order to correct the changing bowel habit due to tumor.
