Introduction

Composite colorectal tumors combining neuroendocrine and glandular neoplastic components are exceptionally uncommon and may present diagnostic and therapeutic challenges [1,2]. Advances in high-definition endoscopy and resection techniques allow effective, minimally invasive treatment when lesions are accurately staged [3].

Methods

A 70-year-old man underwent colonoscopy for evaluation of non-specific abdominal discomfort. Endoscopic examination revealed a 40-mm sessile lesion in the proximal rectum. High-definition white-light and narrow-band imaging demonstrated a mixed pit pattern with glandular and slightly depressed areas, suggestive of early neoplasia limited to the mucosa. An en bloc endoscopic mucosal resection (EMR) was performed after submucosal injection with saline, epinephrine, and indigo carmine. The resection was macroscopically complete, and the procedure was uneventful.

Results

Histopathologic analysis confirmed a composite tumor composed of a well-differentiated NET G1 (trabeculo-microacinar pattern; CKpan+, chromogranin+, synaptophysin+, Ki-67 <3%) and a coexisting intramucosal adenocarcinoma. Both components were strictly confined to the mucosa, with negative lateral and deep margins and no lymphovascular invasion. A contrast-enhanced CT performed after EMR showed no residual disease, regional lymphadenopathy, or complications. The final diagnosis was composite NET G1 and intramucosal adenocarcinoma with R0 resection. Considering the complete removal and low metastatic risk, conservative management was chosen, with follow-up colonoscopy scheduled at 12 months.

Conclusions

This case illustrates that en bloc EMR can be a definitive, minimally invasive treatment for selected composite colorectal tumors when both endoscopic staging and histology confirm mucosal confinement. High-quality imaging, meticulous resection technique, and comprehensive pathology review remain essential to guide optimal management and surveillance in these rare lesions.