Azzopardi effect is a histomorphologic phenomenon of incrustation of blood vessel wall with basophilic nuclear material. It had been primarily described in small cell (neuroendocrine) carcinoma of lung but is nonspecific and can be seen in other malignancies with a rapid cell turnover.
On hematoxylin and eosin (H and E) stained sections, blood vessels within or close to the tumor and in necrotic areas exhibit deeply basophilic staining of the full thickness of the wall.[1]
This phenomenon is named as the Azzopardi effect after John G. Azzopardi, who correctly identified the basophilic material as DNA in 1959. Before his publication, the material was infrequently described in the literature and was presumed to be caused due to calcium deposition. Azzopardi examined 100 cases of oat cell (small cell) carcinoma of lung and identified coarsely granular basophilic material encrusted within venules in 32 cases. He noted a strong association of the vascular phenomenon with tumor necrosis. Blood vessels in necrotic areas revealed smudged hematoxyphilic material which represented DNA released from tumor cells.[1,2]
The granules showed negative staining for calcium with Von Kossa's and alizarin red methods. Azzopardi also demonstrated a positive feulgen reaction in the vascular deposits, suggesting that the basophilic substance was DNA. He subsequently confirmed this by nucleic acid extraction and concluded that this deposition of DNA in the vessel wall is presumably the result of liberation of nucleic acids in large amounts from degenerating neoplastic tissue.[1,2,3]
More than 42 years later, this phenomenon continues to be referred to as the Azzopardi effect, bearing the name of the pathologist who described and interpreted this features.[2,3,4]
To illustrate the phenomenon in oral lesions, H and E stained sections of 20 cases of oral squamous cell carcinoma and 5 cases of salivary gland malignancy were examined thoroughly from the archives of the Department of Oral and Maxillofacial Pathology of our institution. Coarsely granular basophilic incrustation on vessel wall was found in 4 cases of squamous cell carcinoma and 1 case of polymorphous low grade adenocarcinoma.
Azzopardi phenomenon may appear as foci of strongly hematoxyphilic blood vessels which signify chromatin diffusion as a result of necrosis of neoplastic tissue. However, this appearance is a rare occurrence and without any diagnostic implications. Although detected more frequently in lesions such as merkel cell carcinoma and small cell cancer of lung, oral squamous cell carcinoma might infrequently show this feature. The pathologist should be knowledgeable and aware of this intriguing histological feature while evaluating oral carcinoma sections.
A high power view of vessel showing basophilic granules on wall in a case of squamous cell carcinoma along with a hand-drawn illustration is presented in Figure 1. The H and E stained images of the vessel with basophilic incrustation on the wall in a case of polymorphous lowgrade adenocarcinoma is presented in Figure 2.
Figure 1.
(a) Photomicrograph shows a blood vessel containing red blood cells and basophilic incrustation on wall (H&E stain, ×400). (b) Hand-drawn illustration of the same
Figure 2.
(a) Photomicrograph shows basophilic granular deposition on vessel wall with a background of tumor cells and necrosis (H&E stain, ×200). (b): High power view of basophilic granular deposits (H&E stain, x400)
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Conflicts of interest
There are no conflicts of interest.
Acknowledgment
Dr. Sourav Bhattacharya, Associate Professor, Department of Dentistry, Medical College, Kolkata.
REFERENCES
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