Intra-serous haematopoiesis.

Area of Science:

• Hematology
• Cytology
• Pathology

Background:

• Immature hematopoietic cells are typically found in bone marrow.
• Their presence in body fluids like pleural and pericardial effusions is unusual and requires investigation.
• Extramedullary hematopoiesis is a known phenomenon but its occurrence in effusions needs further context.

Purpose of the Study:

• To determine the frequency and types of immature hematopoietic cells in pleural and pericardial effusions.
• To analyze the clinical and biological context associated with their presence.
• To compare findings with existing literature on extramedullary hematopoiesis.

Main Methods:

• Re-examination of cytologically identified samples from pleural and pericardial effusions.
• Analysis of clinico-biological context for 28 cases over 10 years.
• Comparison of findings with published data.

Main Results:

• Immature hematopoietic cells were identified in effusions across various clinical contexts, including sepsis, infection, persistent effusions, and post-transplantation.
• Their presence was not exceptional, even when classical extramedullary hematopoiesis was not suspected.
• Four distinct patient subgroups were identified based on clinical presentation.

Conclusions:

• The identification of immature hematopoietic cells in pleural and pericardial effusions can occur in diverse clinical scenarios.
• A local inflammatory state might facilitate the development of these cells by influencing mesothelial cells.
• Further research is warranted to fully understand the mechanisms and implications of hematopoietic cells in effusions.