Azzopardi phenomenon in cystic pseudotumours associated with retrieved metal-on-metal arthroplasty

SummaryThe Azzopardi phenomenon represents a morphologically well defined lesion characterised by a deposition of basophilic material in the vessel walls associated with several malignant tumours. We report on 4 cases (3 men and 1 woman) showing the Azzopardi effect in retrieved metal-on-metal arthroplasty unrelated to malignancy. All cases were revised for groin pain and radiological findings of so-called pseudotumours. The Azzopardi phenomenon was seen in cases with cystic pseudotumours characterised by superficial necrobiosis, proliferative desquamative synovitis, finding of metal and corrosion wear particles and cellular infiltration by macrophages. The lesions, which were recognized as bluish substance in the hematoxylin and eosin staining, demonstrated a positive Feulgen reaction. We report on the Azzopardi phenomenon in non-neoplastic cystic pseudotumours from retrieved metal-on-metal arthroplasties. Although clinical relevance of this finding remains unclear, further research is necessary to investigate the possible relationship of this lesion with deliberation of metal ions from metal and corrosion wear particles and their role in a broad spectrum of adverse reactions to metal debris.