HISTOLOGY AND HISTOPATHOLOGY

From Cell Biology to Tissue Engineering

 

Morphological hallmarks facilitating distinction of omental milky spots and lymph nodes: an exploratory study on their discriminative capacity

Cindy G.J. Cleypool1, Claire Mackaaij1, Bernadette Schurink1,2* and Ronald L.A.W. Bleys1*

1Department of Anatomy, Division of Surgical Specialties, University Medical Center Utrecht, Utrecht University, Utrecht and 2Department of Pathology, Amsterdam University Medical Centre, Free University of Amsterdam, Amsterdam, the Netherlands
*Both authors contributed equally

Offprint requests to: Cindy Cleypool, University Medical Center Utrecht, Division of Surgical Specialties: Department of Anatomy, Universiteitsweg 100, P.O. Box 85060, 3508 AB Utrecht, the Netherlands. e-mail: c.g.j.cleypool@umcutrecht.nl


Summary. Background. Omental milky spots (OMSs) are the primary lymphoid structures of the greater omentum. However, the presence of lymph nodes (LNs) has occasionally been mentioned as well. Understanding which lymphoid structures are present is of significance, especially in gastric tumor metastasis; tumor deposits in omental LNs suggest local lymphatic spread, whereas tumor deposits in OMSs suggest peritoneal spread and hence extensive disease. Since LNs and OMSs share morphological characteristics and OMSs might be wrongly identified as LNs, reliable hallmarks facilitating easy discrimination are needed. Materials and method. A series of microscopic morphological hallmarks unique to LNs were selected as potential candidates and were assessed for their discriminative capacity: 1) capsule, 2) trabeculae, 3) subcapsular sinus, 4) afferent lymphatic vessels, 5) distinct B- and T cell regions, and 6) a layered organization with, from the outside in a capsule, cortex, paracortex, and medulla. These hallmarks were visualized by multiple staining techniques. Results. Hallmarks 1, 2 5 and 6 were shown to be the most efficient as these were consistent and discriminative. They were best visualized by Picrosirius red, smooth muscle actin and a B-cell / T-cell double staining. Conclusion. The presence of a capsule, trabeculae, distinct B- and T-cell regions and a layered organization represent consistent and reliable morphological features which allow to easily distinguish LNs from OMSs, especially when applied in combination. Histol Histopathol 35, 1275-1284 (2020)

Key words: Lymph nodes, Milky spots, Greater omentum, Lymphoid tissue, Omentectomy

DOI: 10.14670/HH-18-254