Medication-related osteonecrosis of the jaws: a series of 22 cases highlighting their histopathological features

Abstract

This study aimed to assess the clinicopathological characteristics of medication-related osteonecrosis of the jaw (MRONJ), addressing histopathological features and bone structure. Twenty-two MRONJ patients were retrospectively evaluated for osteonecrosis, osteomyelitis, bacterial colonization, bone resorption, reactive bone, osteon-like structure, lamellar bone, and basophilic lines. Specific staining and fluorescence and polarized light microscopy assessments were also performed. The mandible was significantly more affected by MRONJ. There was a predominance of African-Brazilian women aged sixty and older. Osteomyelitis was present in 82% of patients. Actinomycosis was observed in 36.4% of MRONJ patients. Osteoclasts were absent in MRONJ but bone resorption was often seen. Basophilic lines were observed in more than 80% of the patients. The MRONJ patients exhibited lamellar bone with osteon-like structures. This study provided important insight into MRONJ, demonstrating a diverse histopathological spectrum and infection with Actinomyces and fungi. The condition was characterized by a necrotized lamellar bone structure and more frequently affected the mandible of older women.

Figure 1. Medication-related osteonecrosis: A) Presence of exposed bone in the right alveolar ridge of the mandible. B) Panoramic radiograph showing alterations in bone density in the right posterior mandible. Note the bone sequestrum and vertical pathological fracture.

Figure 2. Medication-related osteonecrosis [hematoxylin and eosin, H&E]: A) Interconnected bone trabeculae that are curved and minimally cellular and interspersed with fibrous stroma. There are also basophilic lines arranged parallel to each other or non-parallel. Obliterated blood vessels surrounded by marked chronic inflammation (acute osteomyelitis) [scale bar: 200 µm] can be seen. B) Different area of the previous case showing curved lamellar bone trabeculae in stromal tissue with many empty lacunae, peritrabecular clefting, and no rimming of osteoblasts similar to fibrous dysplasia [scale bar: 200 µm]. C) Curved and interconnected bone trabeculae of variable thickness displaying peritrabecular clefting. Osteomyelitis, with fibrous stroma replaced by marked chronic inflammation can be seen. There are bacterial colonies compatible with Actinomyces in the upper left corner [scale bar: 200 µm]. D) Necrotic lamellar bone with empty lacunae of variable diameters. Note the osteon-like structures [scale bar: 100 µm]. I) Resorption [scale bar: 100 µm]. E) Actinomyces colonies exhibiting varied sizes and necrotic bone in the upper corner [scale bar: 200 µm]. F) Bacterial colonies (actinomycosis) with radiating clubs [scale bar: 200 µm]. G) Extensive accumulation of confluent bacterial colonies (actinomycosis). Necrotic bone with large bone lacunae [scale bar: 200 µm] is shown. H) Irregular necrotic bone trabeculae exhibiting thick basophilic lines parallel to each other and interspersed with irregular bacterial colonies. The bone surface with resorption is shown [scale bar: 200 µm]. I) Irregular necrotic bone amidst fungi infection compatible with Aspergillosis [scale bar: 50 µm; Grocott-Gomori] .

Figure 3. A) Polarized light microscopy of hematoxylin/eosin-stained tissues highlighting the lamellar feature [scale bar: 200 µm]. B) Medication-related osteonecrosis of the jaw showing lamellar bone and osteon-like structures with strong red fluorescence [scale bar: 200µm].