The literature concerning anal prolapse of polyps in pediatric population is scarce. First, we found 8 adequately documented clinical reports [4-11]. Reported ages of presentation ranged from 2 days to 17 years. Four patients were male and four were female. All patients presented with lower gastrointestinal bleeding and a prolapsed anal mass. Additionally, one presented with spontaneous amputation of the polyp, and two presented with anaemia. All polyps were located in the rectosigmoid region. Four were reported as juvenile polyps, one as an inflammatory polyp, one as an inflammatory pseudopolyp, one as hyperplastic crypts covered with calcified granulation tissue in the context of cap polyposis, and in one case two adenomatous polyps were found. The clinical evolution was favorable, and in only 1 case there was a small recurrence that was resolved with medical management. One case did not report the clinical evolution of the patient. Finally, and trying to be rigorous and exhaustive, we have included the case of a 15-year-old patient with Marshall-Smith syndrome who presented with a polypoid lesion covered by rectal mucosa at the level of the anal margin and who was diagnosed as a cloacogenic polyp. However, we believe that this lesion does not strictly belong to the pathophysiologic spectrum presented here. The main characteristics of these studies are shown in Table 1.
Second, there are some published series of patients in the literature in which explicit reference is made to patients with colonic polyps who have debuted with this clinical presentation [15-21]. Regarding these series it should be considered the literature is mostly based on clinical descriptions provided by the patients, and there is greater heterogeneity. Poddar et al. (1998) reported a series of 236 pediatric patients with polyps and documented 30 cases of anal prolapse. Ukarapol et al. (2007) reported a series of 32 patients with 15 of them (47%) presenting anal prolapse, with these patients also presenting a greater association with the presence of polyposis coli. Haghi Ashtiani et al. (2008) reported a 563 pediatric patients series with colorectal polyps with 7 cases of polyp anal prolapse (1.3%). Akkoyun et al. (2011) conducted a pilot study to validate photography and video as diagnostic tools in the context of pediatric anal lesions and in their series reported anal prolapse of 3 polyps that were subsequently confirmed endoscopically although authors did not report histomorphological findings. In 2014, Lei et al. Reported a series of 322 patients with 8 cases of polyp rectal prolapse (2.5%). In 2015, Rathi et al. published a series of 120 pediatric patients with colorectal polyps and reported 14 cases of rectal prolapse (1 in the polyposis syndrome group and 13 in the non-polyposis group). Lastly, Tripathi et al. (2020) [22] presented a series of 240 pediatric patients affected by gastrointestinal polyps with a small percentage debuting with a mucosal rectal prolapse, although they did not specify whether this prolapse corresponded to the polyp per se or not. Interestingly, all reported series are Asian. We hypothesize that this could be due to a higher prevalence of gastrointestinal parasitosis in the reported countries, which is a known risk factor for mucosal rectal prolapse and which following the same pathophysiological principle could lead to the anal prolapse of the polyp. The main characteristics of these studies are shown in Table 2.
In relation to the histologic findings of our case, it is an uncommon polyp because it presents low-grade dysplasia and because it presents a pathologic immunohistochemical study for PTEN and normal for SMAD4. From the histological point of view, we believe that this is a juvenile polyp (also called retention polyps or formerly inflammatory polyps) with atypical features. The presence of a greater epithelial (glandular) than stromal content, as in our patient, has been correlated with a potential association with juvenile polyposis syndromes. Hamartomatous polyps characteristic of Peutz-Jeghers syndrome, on the other hand, usually present a greater smooth muscle component and greater arborization than in our case. In our case, the immunohistochemical study for desmin showed isolated scarce traces of smooth muscle. Also, we consider it difficult to establish the diagnosis of hamartomatous polyp (Peutz-Jeghers) with a large bowel polyp exclusively. On the other hand, we believe that other entities such as CAP polyposis syndrome, cloacogenic polyps or solitary rectal ulcer are framed within the pathology of the anal canal and should not be included in the differential diagnosis of the lesion presented here [23,24].
As a reflection, we believe that this clinical entity (polypoid anal prolapse) is probably underdiagnosed, probably due to the intermittent nature of the prolapse and the indolent course that most patients usually present. Therefore, we subscribe to the report by Akkoyun et al. and believe that the use of photographs and videos to characterize the lesion by parents is a simple and inexpensive way to improve the diagnostic yield in this pathology.
The main strength of this work is the rigorous and adequately characterized description of the case, accompanied by an extensive and reasoned analysis of the previously existing literature. As a limitation, it should be considered that the literature review has not been systematic and therefore there may be papers that have not been included in it.
In conclusion, although the clinical presentation of a polyp as an anal prolapse is uncommon, it should be considered in the differential diagnosis of anal tumors. This presentation may be somewhat more prevalent in cases of hamartomatous polyps, like ours [25]. Other entities should also be considered in the diagnosis of an anal mucosal mass, such as mucosal rectal prolapse, haemorrhoids or infrequent lesions in this location such as lipomas [26]. Although most lesions correspond to juvenile or retentive polyps, histopathologic confirmation is essential to adequately characterize the lesion and to rule out the presence of dysplasia. Based on current evidence, there does not appear to be an association between this clinical presentation and polyposis syndromes.