Massive Mixed Adenoneuroendocrine Carcinoma: A Case Report

Area of Science:

• Gastroenterology and Oncology
• Pathology
• Medical Imaging

Background:

• Mixed adenoneuroendocrine carcinoma (MANEC) is a rare gastrointestinal malignancy characterized by distinct adenocarcinoma and neuroendocrine components.
• MANEC diagnosis requires specialized histological and immunohistochemistry (IHC) analysis, and these tumors are associated with a poor prognosis due to their aggressive nature.

Observation:

• A 70-year-old female presented with abdominal pain and hematemesis, revealing a large gastric mass with extension and lymphadenopathy on CT.
• Endoscopy showed an ulcerated gastric mass; biopsy confirmed mixed poorly differentiated adenocarcinoma and neuroendocrine carcinoma.
• Further imaging revealed extensive pulmonary emboli, liver lesions, ascites, and rapid tumor growth.

Findings:

• The adenocarcinoma component was positive for CDX2 and pancytokeratin; the neuroendocrine component stained positive for synaptophysin and chromogranin.
• The patient experienced rapid clinical deterioration with significant tumor burden progression.
• The case illustrates the aggressive behavior and poor prognosis of MANEC.

Implications:

• MANEC represents a rare and aggressive subtype of gastrointestinal tumors, often presenting late with advanced disease.
• Understanding the pathophysiology and developing standardized therapeutic strategies for MANEC are crucial.
• Early diagnosis and treatment, potentially including surgery or chemotherapy, may improve outcomes in select cases, though options are limited.