Morphometry of normal human lymphoid tissues. Nuclear invaginations and clefts

Area of Science:

• Pathology
• Hematology
• Cell Biology

Background:

• The classification of non-Hodgkin's lymphoma relies on specific morphological features, including the presence of cleaved lymphocyte nuclei.
• Reactive hyperplasia in lymphoid tissue presents a diagnostic challenge, necessitating a clear understanding of normal lymphocyte morphology.

Purpose of the Study:

• To investigate the morphometric basis of the "cleaved" lymphocyte nucleus concept.
• To determine the prevalence and depth of nuclear invaginations in lymphocytes within reactive lymphoid hyperplasia.

Main Methods:

• Morphometric analysis of human lymphoid tissue samples affected by reactive hyperplasia.
• Examination of histologic sections using 1-micron plastic-embedded sections.
• Quantification of nuclear profiles and their invaginations.

Main Results:

• Lymphoid tissue sections showed significant variation in nuclear profiles with invaginations (9-16%).
• True "cleaved" nuclei (invaginations ≥0.4 micron) were found in ≤2% of lymphocytes.
• Most nuclear invaginations were shallow (<1.6 micron), suggesting linear creases rather than deep clefts.

Conclusions:

• The "cleaved" appearance of lymphocyte nuclei in reactive hyperplasia is likely an artifact of sectioning and nuclear folding, not a distinct developmental phase.
• Morphometric data do not support a specific "cleaved" nuclear phase during antigen-induced lymphocyte transformation.
• Distinguishing true cleaved nuclei from artifactual appearances is crucial for accurate lymphoma classification.