Analysis of the Misdiagnosis of a Case of Rectal Lymphoid Polyp: a Case Report

Background: Lymphoid polyps are rare benign lesions, mainly in the intestinal tract. But misdiagnosis always happen, because it is dicult to distinguish lymphoid polyp and lymphoma and laterally spreading tumour (LST) solely relying on endoscopic examination. Generally speaking, pathology can help us make a correct diagnosis, but in few cases advanced methods is necessary for diagnosis, such as immunohistochemistry and gene rearrangement. Case Before we performed examination on the patient. The result pointed towards rectal lymphoma and did not support the diagnosis of LSTs of the rectum, so we did not perform ESD. Because of the possibility of missed diagnosis and misdiagnosis of common endoscopic biopsy, we performed endoscopic mucosal resection (EMR) biopsy. The results of postoperative pathology, immunohistochemistry and gene rearrangement supported the diagnosis of lymphoid polyps. Conclusions: The diagnosis of lymphoid polyps always depends on endoscopic examination and pathology. If necessary, advanced methods such as immunohistochemistry and gene rearrangement may be helpful.

towards rectal lymphoma and did not support the diagnosis of LSTs of the rectum, so we did not perform ESD. Because of the possibility of missed diagnosis and misdiagnosis of common endoscopic biopsy, we performed endoscopic mucosal resection (EMR) biopsy. The results of postoperative pathology, immunohistochemistry and gene rearrangement supported the diagnosis of lymphoid polyps.
Conclusions: The diagnosis of lymphoid polyps always depends on endoscopic examination and pathology. If necessary, advanced methods such as immunohistochemistry and gene rearrangement may be helpful.

Background
Diagnosis is the basis of treatment, even for digestive tract diseases. With the continuous emergence of new endoscopy techniques, the function of endoscopy is becoming increasingly powerful. For experienced endoscopists, many digestive tract diseases can be correctly diagnosed under endoscopy, and some cases can be correctly diagnosed with the help of pathology, but there are still a few cases that cannot be diagnosed by only endoscopy and pathology. Therefore, it is important to combine clinical symptoms with other imaging examinations for diagnosis. If necessary, advanced methods such as immunohistochemistry and gene rearrangement should be used for diagnosis.
We report one case that was rst misdiagnosed as LST without biopsy by an unexperienced endoscopist and then was de nitively diagnosed as lymphoid polyp by pathology, immunohistochemistry and gene rearrangement.

Case Presentation
The patient, female, 56 years old, was hospitalized in the outpatient department of the external hospital on January 16, 2019, due to intermittent haematochezia for half a year. The rst colonoscopy examination showed that a at protuberance could be seen near the anal margin of the rectum, accounting for approximately 1/2 of the intestinal cavity, with a granular surface. Then, laterally spreading tumour (LST) of the rectum was diagnosed without biopsy, and the patient was admitted to the digestive ward of Nanjing Drum Tower Hospital for endoscopic submucosal dissection (ESD) treatment.
The stool occult blood test (immunoassay) was positive. The tumour markers were as follows: CA-199: 29.42 u/ml; CA-242: 16.32 u/ml. Routine blood and biochemical tests were normal. The second colonoscopy examination in gastroentorolgy department of Nanjing Drum Tower Hospital showed a large number of granular nodules near the anal margin of the rectum without an obvious boundary, the pit pattern was type II after indigo carmine staining, and a large number of dilated vessels could be seen in magnifying endoscopy ( Figure. 1 A-D). We found that the possibility of diagnosing lymphoma is high.

Discussion
Lymphoid polyps are more common in adolescents and children than in adults. Its incidence in males is slightly higher than that in females. It can be localized as multiple nodular hyperplasia or, to a lesser The aetiology of the disease is considered to be related to immune de ciency in the body. It has also been reported that agellate and Helicobacter pylori infection are involved in the pathogenesis of the disease [7]. At present, most people believe that lymphoid polyps are a self-limited disease with a good prognosis, but some scholars believe that the disease has a tendency towards a low degree of malignant change.
Because of the di culty of preoperative diagnosis, if the malignant change cannot be excluded or repeated gastrointestinal bleeding is di cult to control, surgery is still recommended. In this case, after communication with the patient, she agreed to regular endoscopy follow-ups.
The concept of LST was rst proposed by Professor Kudo Sinea in 1993. LSTs are generally de ned as super cial lesions ≥10 mm in diameter that typically extend laterally rather than vertically along the colonic wall [8-11]. According to its surface morphology, it can be categorized into 2 subtypes: granular type and nongranular type. Among them, the endoscopic characteristics of the granular type are similar to those of lymphoproliferative diseases, such as lymphoid polyps. Without careful observation, they are easily confused with each other, but the pathological results of biopsy are helpful for endoscopists to make correct diagnosis.
There are three types of morphological characteristics of lymphoma under endoscopy: diffuse type, polyp type and ulcer type. Among them, the polyp type is very similar to lymphoid polyp. In addition to histopathological detection, it is often necessary to use immunohistochemistry or even gene rearrangement technology to distinguish between the different types of lymphoma and lymphoid polyps [12]. In this case, we used colonoscopy (CF-HQ290/OLYMPUS) to carefully observe the lesions according to the sequence of conventional white light colonoscopy, chromoendoscopy, magnifying chromoendoscopy. We found that the possibility of diagnosing lymphoma is high. Considering that it is di cult to make a diagnosis by ordinary biopsy, we performed endoscopic mucosal resection (EMR) biopsy.The pathological results showed that lymphoid tissue hyperplasia and lymphoid follicular formation in rectal mucosa, which was consistent with lymphoid polyps. CD3 and CD20 immunostains showed the typical distribution of T-lymphocytes in the follicles and B-lymphocytes in the intervening zones between the follicles, respectively. However, high ki-67 proliferating indicated high degree of malignancy. Therefore, we perfected monoclonal immunoglobulin gene rearrangement further and the results showed that no immunoglobulin clonal gene rearrangement was detected, which was consistent with lymphoid polyps. In conclusion, we made the correct diagnosis of lymphoid polyps. Gene rearrangement is a normal process in the body. Normal lymphocytes are polyclonal during development, but lymphoma is a monoclonal rearrangement, showing a single pattern of rearrangement in genes; that is, all tumour cells have the same immunoglobulin or TCR gene rearrangement. Because of the high correlation between gene rearrangement analysis and traditional morphological diagnosis and classi cation, gene rearrangement has high speci city (99%) and appropriate sensitivity (83%) in the diagnosis of lymphoproliferative diseases [13]. No immunoglobulin clonal gene rearrangement was detected in this case, which supports the diagnosis of lymphoid polyps.
The causes of misdiagnosis in the rst colonoscopy were analysed as follows: (i) The initial endoscopist did not know enough about the disease of lymphoid polyps and did not pay enough attention in the examination process. This endoscopist made a wrong diagnosis because he/she saw only part of the lesion and did not perform a biopsy.

Declarations Acknowledgments
We would like to thank all members who were associated with this case for their expert technical assistance, helpful comments and general support.

Authors' contributions
Yong-Ting Lan and Hua-Shang contributed equally to the work.

Funding:
This work was supported by grants from the Key Project of Zibo city (2018kj010098), the Key Project of Zibo city (2019gy010045 .

Availability of data and materials
The dataset supporting the ndings and conclusions of this case report is included within this article.

Ethics approval and consent to participate
The study has been approved by the Ethics Committee of Nanjing Drum Tower Hospital in Prague in compliance with the Helsinki Declaration.

Consent for publication
Consent was obtained for the publication of this case report.

Competing interests
The authors declare that they have no competing interests.   Endoscopic mucosal resection (EMR) was performed to get a more accurate endoscopic biopsy. The pathological results of EMR biopsy showed that lymphoid tissue hyperplasia and lymphoid follicular formation in rectal mucosa.