Primary small rectal neuroendocrine tumor with pelvic lateral lymph nodes metastasis: A case report and review of literature.

Abstract

Introduction and importance: Neuroendocrine tumors (NETs) can occur in almost any organ of the body, and they vary in size and volume. The small tumors may be <1 cm in size, but the large ones can exceed 20 cm. The probability of developing NETs in different organs varies greatly, but rectal NETs are relatively common. Our aim is to tell the surgeon that rectal NETs metastasize to the pelvic lateral lymph nodes even in the early stages and small sizes.

Case presentation: In this report, we present the case of a 47-year-old man who was asymptomatic and incidentally diagnosed with a small NET in the rectum during an enteroscopy for physical examination. The diagnosis was confirmed by pathological examination of the biopsy. The CT of the patient was performed pre-hospital for daily physical examination, but nothing could be seen in the rectum from the CT. Then, the diagnostic local resection and a wide free margin was performed on the patient, and a second operation (radical resection of rectal cancer and extensive lateral pelvic lymphadenectomy) was performed due to the post-operative pathological report and the discovery of enlarged pelvic lymph node by PET-CT (positron emission tomography CT). After the surgery, the patient is in good condition and have no other symptoms except for a slight feeling of defecating.

Clinical discussion: NETs could metastasize to the pelvic lateral lymph nodes, if so, the Total mesorectal excision (TME) should be performed, and the invasion and metastatic spread in NETs have to do with the regulatory factor named snail1 and Foxc2. We find that there is no standardized treatment approach for rectal NETs, which should be neither overtreated nor undertreated as far as possible, so the timing of surgery plays an important role, and long-term follow-up of the patients is extremely important.

Conclusion: The purpose of the presentation of this case is to highlight the potential for rectal NETs to metastasize to the pelvic lateral lymph nodes even in the early stages and small sizes, without muscular layer or neurovascular invasion, and lateral lymph node dissection were necessary, emphasizing the importance of timing for surgery.