[Rectal tumor differentiating into neuroendocrine lineage:a case report]

Area of Science:

• Gastroenterology and Oncology
• Pathology

Background:

• Colorectal cancer screening and diagnosis
• Understanding of mixed-type colorectal tumors

Observation:

• A 79-year-old woman presented with a 30-mm lateral spreading tumor in the lower rectum.
• Initial colonoscopy revealed a nodular, mixed-type, granular lesion.

Findings:

• Endoscopic submucosal dissection showed a predominantly adenoma-type tumor.
• Pathology revealed neuroendocrine carcinoma markers (synaptophysin, CD56-positive, chromogranin A-negative).
• Vascular invasion and lymph node metastasis of the neuroendocrine carcinoma component were confirmed after surgical resection.

Implications:

• This case highlights a rare coexistence of colorectal adenoma and neuroendocrine carcinoma.
• Accurate pathological diagnosis is crucial for managing complex rectal neoplasms.
• The findings underscore the need for comprehensive evaluation of rectal tumors, especially those with concerning features like vascular invasion.