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Presented by Pedram Argani, M.D. and prepared by Mohammed Lilo, M.D.
Case 1: This is a 61 year old female with cytokeratin positive cells in the sinuses of her mediastinal lymph node.
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1. Question
Week 581: Case 1
This is a 61 year old female with cytokeratin positive cells in the sinuses of her mediastinal lymph node. The lymph node was found to be slightly enlarged during her coronary artery bypass graft procedureimages/Lilo/Arg-1-1.jpg
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images/Lilo/Arg-1-5.jpgCorrect
Answer: Hyperplastic mesothelial cells
Histology: At low power, this looks like a reactive lymph node. On closer inspection, some of the cells in the sinuses are not sinus histiocytes, but instead are more epithelioid with a crisper nuclear membrane and well defined eosinophilic cytoplasm. The borders of these cells have a somewhat ruffled appearance. These are the cells which label strongly for cytokeratin. The cells also label for calretinin (image below), consistent with displaced hyperplastic mesothelial cells
Discussion: Metastatic carcinoma would involve the sinus, but would typically feature cells with greater atypia and these cells would not label for calretinin. Sinus histiocytes do not label for cytokeratin. Fibroblastic dendritic reticulum cells may label for low molecular weight cytokeratins, but these are spindled in morphology and are located in the paracortex, not the sinuses.
Hyperplastic mesothelial cells are a well-recognized mimic of metastatic carcinoma involving lymph nodes, with the typical locations being the peritoneal and the mediastinal lymph nodes. These are almost always associated with chronic effusion or serositis, and likely reflect drainage of exfoliated mesothelial cells in these serosal spaces into lymphatics and then into lymph nodes.
Reference(s):
– Am J Clin Pathol 1990; 93:741-8
Hum Pathol 1998; 29:339-346.Incorrect
Answer: Hyperplastic mesothelial cells
Histology: At low power, this looks like a reactive lymph node. On closer inspection, some of the cells in the sinuses are not sinus histiocytes, but instead are more epithelioid with a crisper nuclear membrane and well defined eosinophilic cytoplasm. The borders of these cells have a somewhat ruffled appearance. These are the cells which label strongly for cytokeratin. The cells also label for calretinin (image below), consistent with displaced hyperplastic mesothelial cells
Discussion: Metastatic carcinoma would involve the sinus, but would typically feature cells with greater atypia and these cells would not label for calretinin. Sinus histiocytes do not label for cytokeratin. Fibroblastic dendritic reticulum cells may label for low molecular weight cytokeratins, but these are spindled in morphology and are located in the paracortex, not the sinuses.
Hyperplastic mesothelial cells are a well-recognized mimic of metastatic carcinoma involving lymph nodes, with the typical locations being the peritoneal and the mediastinal lymph nodes. These are almost always associated with chronic effusion or serositis, and likely reflect drainage of exfoliated mesothelial cells in these serosal spaces into lymphatics and then into lymph nodes.
Reference(s):
– Am J Clin Pathol 1990; 93:741-8
Hum Pathol 1998; 29:339-346.
