# Case Report: Pulmonary enteric adenocarcinoma harboring KRAS/TP53/APC mutations with contralateral lung metastasis: diagnostic challenges and molecular insights

## TL;DR

A rare case of bilateral lung cancer with features of colorectal cancer is reported, highlighting the need for molecular testing to guide diagnosis and treatment.

## Contribution

This case presents a rare instance of synchronous bilateral PEAC with specific molecular mutations, offering insights into diagnostic challenges.

## Key findings

- The patient had glandular structures resembling colorectal adenocarcinoma with CDX2, CK20, and SATB2 positivity.
- KRAS, TP53, and APC mutations were identified, indicating a colorectal-like oncogenic pathway.
- Integrated molecular and immunophenotypic profiling is crucial for distinguishing PEAC from metastatic colorectal cancer.

## Abstract

Pulmonary enteric adenocarcinoma (PEAC) is a rare subtype of lung adenocarcinoma characterized by intestinal differentiation. We report a case of synchronous bilateral PEAC in an elderly male patient, a presentation that is rarely documented in the literature. Histopathological examination revealed glandular structures resembling colorectal adenocarcinoma, with immunohistochemical positivity for CDX2, CK20, and SATB2, and negativity for TTF-1 and CK7. Molecular testing identified concurrent KRAS, TP53, and APC mutations, suggesting the activation of a colorectal-like oncogenic pathway. Following surgical resection and adjuvant chemoradiotherapy, the patient achieved short-term disease stability. This case highlights the diagnostic dilemma between primary PEAC and metastatic colorectal cancer and underscores the importance of integrated molecular and immunophenotypic profiling for accurate classification and potential targeted therapy.