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Polymorphous low grade adenocarcinomas (PLGAs) are thought to be indolent tumours that are localised preferentially to the palate and aVect the minor salivary glands almost exclusively. Metastases to locoregional lymph nodes occur in only 6-10% of cases. Recently, two cases of PLGA with microscopically confirmed distant metastases have been reported. This study reports a third case of PLGA with histologically and immunohistochemically confirmed distant metastases. It is the first case with multiple pleural, as well as pulmonary parenchymal, metastases and metastases in cervical and paraoesophageal lymph nodes. In most cases, PLGAs are salivary gland tumours with limited potential to metastasise and a good prognosis after local treatment. However, the recently reported cases reveal that the tumour can give rise to widely spread metastases. To obtain more information about the incidence of distant metastases, periodic chest x ray examination during follow up is desirable. (J Clin Pathol 2000;53:942-945)

These results suggest that only vessels with a diameter larger than 10 microm, consistent with functional vessels, play a role in the process of metastasis. Further research more specifically into structural and functional characterization of blood and lymphatic vessels might help provide more insight into the relationship between microvasculature and the pathogenesis of metastasis in tongue carcinomas.

The aims of this study of head and neck tissue samples were to develop an immunohistochemical protocol based on the catalysed reporter deposition (CARD) technique to enhance staining results for use in automated true colour image analysis, to assess the reproducibility of systematic tissue sampling in the angiogenic hot spot selection, and quantification of microvessel density (MVD) and other vessel characteristics. The latter data were compared between six metastasised tongue squamous cell carcinomas, vs. four non-metastasised. In comparison to the standard immunohistochemical protocol with anti-CD34 antibodies, CARD amplification resulted in both more intensely stained and larger numbers of vessels. Averaging the 10 most vascularised fields of the 40 to 60 systematically sampled fields in a tissue section resulted in an overall acceptable interobserver reproducibility for most assessed vessel parameters (r ≧ 0.76 and p ≦ 0.01). The percentage vessels with diameter <5 μm was significantly higher in the non-metastasised tongue carcinomas (p = 0.02). However, for a number of tumours the effect of tissue sampling was significant. We conclude that CARD amplification is needed for reliable segmentation of vessels by image analysis systems, and that tumour heterogeneity is a limiting factor for all procedures in which tumour vascularity is assessed in a single tissue section.

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