Endoscopic ultrasound‐guided fine‐needle aspiration diagnosis of merkel cell carcinoma metastatic to the pancreas

Abstract

Merkel cell carcinoma (MCC) is a rare and highly aggressive primary neuroendocrine carcinoma of the skin with a high propensity for local, regional, and distant spread. Distant metastasis of MCC to the pancreas is uncommonly seen and may impose a diagnostic challenge cytologically. Here we report a case of MCC with pancreatic metastasis, which was diagnosed by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). The aspirates revealed both single and clustered epithelial cells with scant cytoplasm and round nuclei with stippled chromatin and inconspicuous nucleoli. Immunocytochemically, the tumor cells were positive for CK20, synaptophysin, CD56, and CD117. The neoplastic cells were also identified by flow cytometry as non-hematopoietic cells which were positive for CD56 and negative for CD45. To our knowledge, this is only the second case report of MCC metastatic to the pancreas diagnosed by EUS-FNA. There have been several reports of MCC metastatic to the pancreas diagnosed only at the time of surgical resection. However, a preoperative diagnosis allows for appropriate management while sparing a patient the morbidity of unnecessary procedures.

The diagnostic utility of Merkel cell polyomavirus immunohistochemistry in a fine needle aspirate of metastatic Merkel cell carcinoma of unknown primary to the pancreas

“…23 However, metastases to the pancreas are exceedingly rare; only 19 cases have been reported in the literature. [7][8][9][10][11][12][13][14][15][16][17][18][19] In these cases, the pancreas metastases were almost always preceded by nodal recurrence of primary MCCs or concomitant extra-pancreatic metastases.…”

“…[4][5][6] Pancreatic involvement by MCC is rare with 19 reported cases in the literature. [7][8][9][10][11][12][13][14][15][16][17][18][19] To date, only 8 cases have been diagnosed by endoscopic ultrasound-guided fine-needle aspiration cytology (EUS-FNA). 8,18,19 We report a case of MCC from an unknown primary manifesting as an axillary mass and a pancreatic metastasis.…”

Metastatic Merkel cell carcinoma (MCC) of pancreas and breast: a unique case

“…Patient symptoms are usually local or secondary to tumor growth or lymph node involvement. Most patients have localized disease at initial presentation (70–80%) [2,4]; the majority develop metastatic disease, either synchronously or metachronously with a frequency varying from 20–75% [4]. It has a penchant for local recurrence and distant metastasis to various sites, including regional lymph nodes, distant skin, lung, liver, testis, and other rare organs such as the pancreas [1-3,5].…”

Imaging in Patients with Merkel Cell Carcinoma

“…Except for a few published case reports, ultrasound guided and nonguided fine needle aspiration biopsy has been rarely described in MCC patients [19–23]. Definitive diagnosis of metastatic disease is challenging with fine needle aspiration cytology alone [20]. The cytomorphology resembles numerous other malignancies such as malignant lymphoma and malignant melanoma [23].…”