Pathology and Histochemistry

Abstract

Lymphedema is a consequence of pathological obstruction of main lymphatic trunks draining limbs or organs. It is a symptom and not a separate entity. Edema reflects events developing in tissues, such as accumulation of capillary filtrate in the intercellular space, hypertrophy of fibroblasts and adipocytes, and retention of microorganisms continuously penetrating the sole or palm skin evoking chronic inflammatory response. The causes of damage of lymphatic collectors are different, with most common being bacterial infections of limb soft tissues, followed by tissue trauma and lymphadenectomy and radiotherapy in tumors. Less common causes are chronic venous insufficiency with dermosclerosis and filariasis. Lymphoscintigraphy, indocyanine green lymphography, ultrasound of tissues, and magnetic resonance imaging help to evaluate changes in main lymphatics and nodes and location of edema fluid and fluid outflow pathways through spontaneously formed tissue channels and subepidermal plexus. The main histological changes in soft tissues are lymphatic collectors with lumen occluded by collagen and other acellular masses and lack of endothelial and muscle cells, dilated subepidermal lymphatics, enlarged tissue spaces with proteinaceous fluid, hyperkeratosis, and fibrosis of the dermis, subcutaneous tissue, and fascia. Electron microscopic pictures reveal presence of intercellular fluid and open interendothelial junctions in subepidermal lymphatics. Bacterial cells are seen widely spread but not forming colonies.