The microTCV form is associated with aggressive features at presentation, and it should be differentiated from other papillary thyroid microcarcinomas.
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.
Background:Pancreatic neuroendocrine tumors (PNETs) are rare tumors of the pancreas, which are increasingly diagnosed by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). In this retrospective study, we assessed the performance of EUS-FNA in diagnosing PNETs.Materials and Methods:We identified 48 cases of surgically resected PNETs in which pre-operative EUS-FNA was performed. The clinical features, cytological diagnoses, and surgical follow-up were retrospectively reviewed. The diagnostic performance of EUS-FNA was analyzed as compared to the diagnosis in the follow-up. The cases with discrepancies between cytological diagnosis and surgical follow-up were analyzed and diagnostic pitfalls in discrepant cases were discussed.Results:The patients were 20 male and 28 female with ages ranging from 15 years to 81 years (mean 57 years). The tumors were solid and cystic in 41 and 7 cases, respectively, with sizes ranging from 0.5 cm to 11 cm (mean 2.7 cm). Based on cytomorphologic features and adjunct immunocytochemistry results, when performed, 38 patients (79%) were diagnosed with PNET, while a diagnosis of suspicious for PNET or a diagnosis of neoplasm with differential diagnosis including PNET was rendered in the 3 patients (6%). One case was diagnosed as mucinous cystic neoplasm (2%). The remaining 6 patients (13%) had non-diagnostic, negative or atypical diagnosis.Conclusions:Our data demonstrated that EUS-FNA has a relatively high sensitivity for diagnosing PNETs. Lack of additional materials for immunocytochemical studies could lead to a less definite diagnosis. Non-diagnostic or false negative FNA diagnosis can be seen in a limited number of cases, especially in those small sized tumors.
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