Angiogenesis in lymph node metastases

Angiogenesis in lymph node metastases Sir: In the paper published by Naresh et al. in the May issue of Histopathology concerning the redundant role of neoangiogenesis for tumour growth in lymph node metastases, the authors compared the microvessel counting of primary head and neck squamous cell carcinomas (PT), uninvolved mucosa (UM), non-metastatic lymph nodes (NML), and metastatic (ML) nodes. They assessed the vessel count using a grid (100 grid spaces of 0.25 mm each) in a ́20 objective and ́10 eyepiece in double-immunostained histological preparations with antibodies raised against factor VIII-related antigen and Ki67. To evaluate the primary tumour and the metastatic lymph nodes the authors placed the grid on the peripheral portions of the neoplastic lesions; in the sections from uninvolved mucosa and non-metastatic lymph nodes, the grid covered almost the entire section. In addition, they discounted vessels with thick smooth muscle coat. With this methodology, they found that the non-metastatic lymph nodes signi®cantly showed the highest vessel counts (mean of 224) when compared with PT (mean of 157.9), UM (mean of 69.2), and ML (mean 145.2). Conversely, when they assessed the vessels with Ki67+ endothelial cells, they observed statistically signi®cantly higher ®gures in the PT when compared with UM, NML, and ML. To the best of our knowledge, this is the ®rst study to apply this methodology to assess these angiogenic parameters. The authors had neither adhered to Weidner et al. criteria to determine microvessel densities nor considered angiogenic hotspots to place their grid. In the very important review of angiogenesis published by Fox, he made a strong case concerning the importance of following a previously validated method or validating the results of a new methodology by using the Weidener's method or Chalkley counting. In the discussion, the authors state that there is a lack of speci®c markers to objectively identify neovasculature. We agree with them; however, endoglin, an accessory component of the transforming growth factor-beta-binding receptor complex, has been used to highlight the new-formed vessels with very interesting results, including one paper showing its independent prognostic factor for patients with breast carcinoma. In addition, Eberhard et al., in 2000, described an immunohistochemical method to assess vessel maturation that is somewhat similar in some aspects to the one adopted by the authors. However, due to both different study design and tumours evaluated, these two studies are not comparable. Concerning the exclusion of the vessels with thick smooth muscle coat in the vessel counting, we have some doubts about the validity of this methodology. Recently Giatromanolaki et al. showed that Edvin categories (edge versus inner microvessel densities (MVD)) presented very useful predictive and prognostic information for patients with non-small cell lung carcinoma. Brie ̄y, they demonstrated that Edvin 1 (tumours with low MVD at the edge and centre) tumours presented a better prognosis that Edvin 2 (tumours with high MVD at the edge and low at the centre) tumours, and Edvin 3 (tumours with high MVD at the edge and centre). Because we consider that in tumour biology the edge is the future and the centre is the past, these data have outstanding importance, because they demonstrate that: (i) vascular proliferation (neoangiogenesis) is important, but vascular survival at the centre of a tumour is also; (ii) mature vessels, as observed in the centre of the neoplasms, are also important for the biological behaviour of the tumours. In addition, Naresh et al. speculated about the role of angiogenic molecules in the pathogenesis of primary lymph node tumours, stated that new-formed blood vessels might be easier targets than pre-existing channels for metastatic access by the invasive tumour cells, which might facilitate the vessel invasion and distant metastasizing, and concluded that neoplastic cells that reach lymph nodes may not be dependent on the formation of new blood vessels for their growth. We concur with the statement that, theoretically, new formed vessels are easier to be invaded than preexisting channels; however, the routine microscopic analysis of human solid tumours usually demonstrates that neoplastic in®ltration destroys the pre-existing solid tissues much more frequently than the pre-existing and the new-formed vessels, and that lymphatic vessel invasion is much more frequent than newformed blood vessel invasion. In addition, some reports speculate about a putative protection and sustaining of the neovasculature at the tumour edge. Finally, we must remember that the NMLs evaluated in this study were also subjected to angiogenic factors produced by neoplastic cells, and that this in ̄uence might have increased the vessel counts, as well as that neoplastic growth in the lymph node completely disrupts its normal architecture, which may impair the comparisons between normal and metastatic lymph