University of Washington Seattle, WA, United States
Linhchi Pham, MD, Yutaka Tomizawa, MD, MSc University of Washington, Seattle, WA
Introduction: Merkel cell carcinoma (MCC) is a rare but highly aggressive cutaneous malignancy with neuroendocrine features. The incidence is estimated from 0.1 to 1.0 to 9.8 (per 100,000 person-years) among age groups 40-44 years, 60-64 years, and ≥ 85 years, respectively. Merkel cells, which are present in the basal layer of the epidermis, are associated with afferent sensory nerves and express neuroendocrine markers such as chromogranin‑A, synaptophysin and cytokeratin 20 (CK20). Diagnosis of MCC is often delayed due to non-specific presentations and almost one‑third of patients present with loco‑regional metastases or lymph node metastases.
Case Description/Methods: An 81-year-old man with a history of prostate cancer and well-controlled Merkel cell carcinoma (MCC) of the skin was referred for an upper endoscopic ultrasonography (EUS) to evaluate a newly found porta-caval lymph node identified on a contrast-enhanced computed tomography (CT) scan of the abdomen (Fig. A). Given his history of two distinct cancers, tissue acquisition was critical for further systemic therapy. Endoscopic ultrasound (EUS) demonstrated a 40 x 25 mm, well-circumscribed, hypoechoic mass and EUS-guided fine-needle aspiration (FNA) was performed (Fig. B). Cytopathology evaluation revealed discohesive relatively small to moderate size malignant cells with hyperchromatic nuclei with condensed chromatin, absent nucleoli, scant cytoplasm and numerous mitotic figures (Fig. C). Immunohistochemical stains were positive for synaptophysin (Fig. D) and focally positive for CK20. The morphology was similar to this patient's previous Merkel cell carcinoma in a previous biopsy and these findings were diagnostic for metastasis of Merkel cell carcinoma (MCC). No other progressive disease was identified elsewhere on positron emission tomography (PET)-CT. He underwent single fraction radiation therapy to the lesion. He resumed immunotherapy and is currently under close surveillance.
Discussion: Several previous reports demonstrated the clinical utility of EUS-FNA for MCC metastatic to the pancreas parenchyma. To the best of our knowledge, our case represents the first report of MCC metastatic to the isolated portacaval lymph node without any distant metastasis. This is a very rare case highlighting EUS-FNA of an isolated portacaval lymph node leading to the diagnosis of MCC metastasis.
Figure: A. Isolated porta-caval lymph node on CT Abdomen. B. Endoscopic ultrasound guided fine needle aspiration of the lymph node. C. Cytopathology with malignant cells with hyperchromatic nuclei. D. Immunohistochemical stains positive for synaptophysin, similar to patient's previous Merkel Cell.
Disclosures: Linhchi Pham indicated no relevant financial relationships. Yutaka Tomizawa indicated no relevant financial relationships.
Linhchi Pham, MD, Yutaka Tomizawa, MD, MSc. P0115 - EUS-FNA Was Diagnostic for an Isolated Portacaval Lymph Node: A Rare Case of Merkel Cell Carcinoma, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.
