Minimum spanning tree, integrated optical density and lymph node metastasis in bronchial carcinoma

Surgical specimens comprising 80 primary lung carcinoma (lobes and lungs) were expanded by insufflation of air into the main bronchi, and fixed with buffered formalin for 24 h. After the usual tissue procedures, 3-4 microns thick histological sections of the tumour mass were Feulgen stained and various nuclear features such as integrated optical density (IOD), area, form factor, etc. were measured using an automated image analysing system (VISIAC). The geometrical centres of the nuclei were defined as vertices and the corresponding minimum spanning tree (MST) was calculated according to the distance between the vertices. The tumour mass was measured by serial sections of the surgical specimens; the lymph node stage was defined according to the rules of the UICC. Non-tumour infiltrated lymph nodes of the same case served as controls for the IOD and MST. The results revealed a DNA index of 1.1-3.0, a malignancy index (Böcking) 0.90-1.08 and a percentage of S-phases 10-23% (confidence limits). Only 19% of the bronchial carcinoma were found to be not aneuploid. Based upon the weighted MST, the distance of neighbouring cells, the IOD of the centre cells and IOD/area of neighbouring cells revealed statistically significant differences between tumours with and without lymph node metastases. The more advanced the lymph node stage, the 'closer' was the 'packing' of the tumour cells.