Clinicopathological analysis of neuroendocrine carcinoma discovered incidentally in hemorrhoids: A case report and literature review.

The present study describes the clinical, histopathological and immunohistochemical features of a case of neuroendocrine carcinoma (NEC) incidentally discovered in hemorrhoidal tissue of a 46-year-old female patient, and also reviewes the relevant literature. The patient was admitted because a colonoscopy revealed hemorrhoids, accompanied by diarrhea. Following surgical resection, pathological examination revealed that the majority of the specimen was hemorrhoidal tissue, with intravascular tumor thrombus and a focus of poorly differentiated NEC (maximum diameter of ~0.5 cm) in the mucosa and submucosa of a single tissue. Furthermore, immunohistochemical results showed a 95% Ki-67 proliferation index and positivity for pan-cytokeratin, chromogranin A and synaptophysin. However, special stains such as Alcian blue and periodic acid-Schiff were negative. Subsequently, the patient received chemotherapy. The 6-month postoperative follow-up computed tomography revealed suspicious metastatic lesions in the perirectal fat space. Subsequent pathological examination of percutaneous needle biopsy specimens confirmed metastatic poorly differentiated NEC. Following confirmation of the diagnosis, the patient underwent radical resection for anal canal carcinoma. The patient reported multiple metastases and signs of systemic failure at 23 months of follow-up. Based on this case and limited literature reports, poorly differentiated NEC of the anal canal incidentally detected in hemorrhoidal tissue-particularly those accompanied by intravascular tumor thrombus and a high Ki-67 index-may indicate high aggressiveness. Long-term and close postoperative monitoring is recommended. Owing to the rarity of such cases, their universal invasive characteristics and the optimal treatment regimen still require validation with more clinical data. The findings of this study can provide a reference for clinical diagnosis and management.