  Although the lymphatic system is clearly linked to the metastasis of most
human carcinomas, the mechanisms by which lymphangiogenesis occurs in response
to the presence of carcinoma remain unclear. Hierarchical models are presented
to investigate the properties of lymphatic vessel production in 2997 fields
taken from 20 individuals with invasive carcinoma, 21 individuals with cervical
intraepithelial neoplasia and 21 controls. Such data demonstrate a high degree
of correlation within tumour samples from the same individual. Joint
hierarchical models utilising shared random effects are discussed and fitted in
a Bayesian framework to allow for the correlation between two key outcome
measures: a random cluster size (the number of lymphatic vessels in a tissue
sample) and a continuous outcome (vessel size). Results show that invasive
carcinoma samples are associated with increased production of smaller and more
irregularly-shaped lymphatic vessels and suggest a mechanistic link between
carcinoma of the cervix and lymphangiogenesis.
