Track

Case Reports

Abstract

Background:

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin cancer associated with poor prognosis, particularly in metastatic disease. Tumor-to-tumor metastasis is an uncommon phenomenon in which a primary malignancy metastasizes to another distinct tumor, with meningiomas being the most frequent recipients of metastasis from breast and lung tumors. Warthin tumor, a benign salivary gland neoplasm, is an unusual host for such metastases.

Case Presentation:

A 74-year-old man with a history of non-small cell lung cancer, esophageal cancer, chronic obstructive pulmonary disease, coronary artery disease, peripheral vascular disease, and diabetes mellitus presented with a left neck nodule first noted in January 2024. PET/CT revealed bilateral parotid lesions and metastatic disease to cervical lymph nodes. Examination identified a left lateral neck lymph node adjacent to the parotid. Fine-needle aspiration revealed MCC, and surgical excision of bilateral parotid masses was performed. The left parotid lesion demonstrated a classic Warthin tumor architecture with abundant oncocytic epithelium and lymphoid stroma, infiltrated by metastatic MCC. Immunohistochemistry confirmed neuroendocrine carcinoma consistent with MCC, with CK20 perinuclear dot-like positivity and TTF-1 negativity.

Outcome:

Despite targeted therapy and supportive measures, the patient’s disease progressed, and he succumbed to complications from comorbidities and metastatic cancer.

Conclusion:

This case highlights the rare occurrence of MCC metastasizing to a Warthin tumor. Accurate diagnosis requires careful histopathologic evaluation to distinguish true tumor-to-tumor metastasis from the intrinsic undifferentiated components of the host tumor. Recognition of this phenomenon is essential, particularly in patients with known malignancies, to avoid misinterpretation and ensure appropriate management.