Here is an excerpt from the abstract that basically sums up the whole paper:
"From the point of the physician, the expanding, invasive, colonizing urban form with highly irregular borders resembles a malignant lesion. Malignant neoplasms have at least four major characteristics: rapid, uncontrolled growth; invasion and destruction of adjacent normal tissues (ecosystems); metastasis (distant colonization); and de-differentiation."He lists these four qualities, because in order for a tissue irregularity to be deemed malignant, it must meet 2 out of 4 of them. He then spends the rest of the paper basically showing how modern cities meet all four.
He spends a long time talking about fractal geometry and about the fact that border irregularity is higher in tumors that are malignant as opposed to those that are benign. Similarly, the larger a city a grows, the more irregular the border becomes. Also, both urban communities and tissue malignancies send out satellites, suburbs or lesions respectively. Basically both urban communities and malignant tissues just grow out and out and out with no real purpose other than to just be, and if the main entity can't grow any larger, it sends out little ones to keep the growing going.
As for the de-differentiation (the simplification of cells and tissue to a simplified, unspecialized form), he mentions how once upon a time, ancient cities reflected the local culture in terms of layout and look. However, modern cities basically all look the same. There are of course minor difference, but the bigger a city gets, the more it tends to look like all the other bigger cities.
And of course, the main similarity between urban growth and malignant growth, is that it's just freaking rapid. He lists all kinds of specific examples and you can see in the photo above, how little time it takes for a city to just overwhelm an area. And here's an overall sum of the kind of growth he's talking about:
"Reflecting this is the fact that rapid urban growth has taken place in a context of unprecedented growth of the global human population, which has more than quadrupled in the century from the beginning of the twentieth century to the present-from 1.6 billion to more than 6.6 billion. The proportion of urban population, which was 220 million (13%) in 1900, has grown to 29% (732 million) in 1950, and 49% (3.2 billion) in 2005. By 2030, the 4.9 billion people living in urban agglomerations will represent 60% of the human population."That's a lot of people in not a whole lot of time. And all of this ultimately is a metaphor, because no, urban cities are not cancers, but there are some really creepy similarities. It's hard to deny that any large city hasn't had a negative influence on the ecology surrounding it, and often even it's inhabitants. Malignant cancers grow and feed off the host until it is either treated or it kills the host. They grow and grow without stopping, until they are stopped by outside forces. What city has ever stopped growing unless it was physically stopped?
And here's the part that's somewhat unsettling:
"Death of the host organism in a cancer occurs between the 37th and 40th doubling of the cell population. The human population has doubled its numbers 32.5 times by 1999, but global energy use by human beings has doubled 36 times..."I know I'm a massive cynic and I have a tendency to look for the bad in everything, but I'm pretty sure we're killing the planet. And I mean that in the least hippie-centric way possible.