[1819] Minute Nests of Neuroendocrine Cells in the Mediastinal Lymph Nodes: Real Metastasis?

F Li, X Wang, LA McMahon, Q Yang, H Xu. University of Rochestyer Medical Center, Rochester

Background: It is continuously debatable whether lymph nodes can harbor a primary neuroendocrine tumor. The presence of neuroendocrine cells in rare peri-pancreatic lymph nodes (LNs) suggests that neuroendocrine cell proliferation can arise in situ from neuroendocrine cells native to any LN. It is difficult to determine the clinical outcome just based on the finding of these cells by immunohistochemistry in patients with broncho-pulmonary carcinoids.
Design: Two cases of mediastinal LNs harboring minute nests of neuroendocrine cells in patients with no history of neuroendocrine tumor were reviewed. For comparison, 71 carcinoids including 62 typical carcinoids (TCs) and 9 atypical carcinoids (ACs) with 315 LN biopsies were retrieved. All slides were examined and the sizes of LN metastasis were recorded.
Results: Case 1. The patient was 67 year old man who had a 7.0 cm, hypermetabolic tumor in the left lower lobe of lung detected by CT and PET scans. Lobectomy with LN biopsies was performed. Well-differentiated adenocarcinoma was diagnosed and <1 mm size of nested neuroendocrine cells were identified in level 10 LN. One level 9 and 2 hilar LNs were unremarkable. Case 2. The patient was 74 year old man who had 3.8 cm and 2.0 cm, hypermetabolic tumors in the left hilum and thyroid by PET, respectively. Multiple left neck LNs were hypermetabolic as well. Endobronchial biopsy was performed to show poorly differentiated adenocarcinoma. Total thyroidectomy and left neck lymph node dissection were performed and papillary thyroid carcinoma with multiple LN involvement was diagnosed. Subsequently, LNs including level 5, 6 and 10 were biopsied and <1 mm of nested neuroendocrine cells was identified in level 5 LN. In both case 1 and 2, the neuroendocrine cells were strongly positive for chromogranin, synaptophysin and TTF-1, but negative for calcitonin and thyroglobulin. D2-40 stain failed to detect any lymphatic channels surrounding these cells. Slides of TCs, ACs and LNs were reviewed to show >4 mm in size of individual metastases in 7 involved LNs (62 TCs with 5 positive LNs and 9 ACs with 2 positive LNs) and the morphology of metastatic carcinoids was similar to that of the primary tumors. No <1 mm in size of nested neuroendocrine cells was identified in LNs.
Conclusions: Minute nests of neuroendocrine cell proliferation similar to the histology and protein expression observed in tumorlet of the lung can be incidentally identified in mediastinal LNs. Close clinical followup is warranted although these cells are unlikely metastasized from the lung.
Category: Pulmonary

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 250, Wednesday Morning


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