# Breast Metastasis from Pulmonary Mucoepidermoid Carcinoma in a Male Patient: A Case Report

## TL;DR

A rare case of lung cancer spreading to the breast in a male patient is described, emphasizing the importance of thorough diagnosis and treatment planning.

## Contribution

This case report highlights the exceptional rarity of pulmonary mucoepidermoid carcinoma metastasizing to the breast in a male patient.

## Key findings

- Breast metastasis from pulmonary mucoepidermoid carcinoma is exceptionally rare, especially in men.
- Integration of clinical, imaging, histological, and molecular data was crucial for accurate diagnosis.
- Palliative surgical debulking and systemic therapy with gemcitabine were effective in managing the patient's condition.

## Abstract

Mucoepidermoid carcinoma of the lung is a very uncommon type of tumor that arises from cells similar to those found in the salivary glands. Although it usually grows slowly, some forms can behave aggressively and spread to distant organs. Metastasis to the breast is exceptionally rare, especially in men, and can be difficult to distinguish from a primary breast cancer because the two conditions may look very similar under the microscope. In this report, we describe the case of an elderly male patient who presented with a breast mass that was ultimately found to originate from a lung tumor. The diagnosis required careful interpretation of imaging studies, detailed histological assessment, and molecular testing. This case highlights the importance of considering unusual metastatic pathways and shows how integrating clinical, pathological, and molecular information can guide appropriate treatment decisions.

Mucoepidermoid carcinoma of the lung is a rare salivary gland-type tumor with heterogeneous clinical behavior and the potential to mimic neoplasms arising in other organs. The purpose of this report is to describe an exceptionally uncommon presentation of pulmonary mucoepidermoid carcinoma manifesting as a breast metastasis in a male patient, a scenario that poses significant diagnostic challenges due to its rarity and its morphological resemblance to primary breast carcinoma. We evaluated the patient through clinical examination, cross-sectional imaging, endobronchial procedures, ultrasound-guided biopsy, immunohistochemistry, and molecular analysis, integrating these data to establish the diagnosis. Imaging revealed a primary lung mass and a second lesion in the left breast infiltrating the pectoralis muscle. Biopsy of the breast mass showed high-grade salivary gland-type mucoepidermoid carcinoma, clinically and radiologically suggestive of pulmonary origin. Because the lesion showed signs of impending ulceration, palliative surgical debulking was performed with good postoperative recovery. The patient subsequently began systemic therapy with gemcitabine. This case underscores the need for careful clinicopathologic correlation when evaluating atypical breast lesions and highlights the diagnostic value of molecular testing in distinguishing primary from metastatic salivary gland-type tumors. Recognizing such rare metastatic patterns is essential for appropriate therapeutic planning.