Saturday, October 2, 2010

Germ cell tumors: definition problems

OK, getting back to the prior post on germ cell tumors, we found that the rate of occurrence of seminomatous germ cell tumors of the testes has been greatly increasing, in the white male population, since (at least) 1973. During the same period, the rate of occurrence of the other type of germ cell tumors (non-seminomatous) has hardly increased at all, for white men.

Why has the rate of occurrence of seminomas increased since 1973, in the white male population? Also, if seminomatous and non-seminomatous germ cell tumors are just morphologic variants of the same basic tumor (i.e., germ cell tumor), why wouldn't they both increase to the same extent?

Perhaps some of the problem relates to the definition of these two tumors.

Seminomas are tumors of gonocytes, a differentiated cell committed to producing gametes (sperm in males, eggs in females), or a committed progenitor cell of gamete-producing cells (i.e., an ancestral cell of a gamete-producing cell). Since seminomas are considered the neoplastic equivalent of gonocytes, there seems to be little leeway in their classification: they must be included among the germ cell tumors.

But what about the other type of germ cell tumors. This other type is known by two different names that tell us a lot about the ambivalent nature of the tumor:

From wikipedia:

"The nongerminomatous or nonseminomatous germ cell tumors (NGGCT, NSGCT) include all other germ cell tumors, pure and mixed."

How can a germ cell tumor be non-germinomatous? Wouldn't the adjective "non-germinomatous" pretty much tell you that the tumor can't be a germ cell tumor?

It reminds me of one of my favorite limericks.

As I was sitting in my chair,
I sensed the bottom was not there.
Nor legs, nor back,
But I just sat,
Ignoring little things like that.

- Anonymous

Well, what are the non-germinomatous germ cell tumors? These are tumors that usually arise in the gonads and are composed of primitive pluripotent cells. We can find pure or mixed populations of embryonal carcinoma, teratomatous tissue, and choriocarcinoma in the non-germinomatous germ cell tumors. These are the same cells that are found in the very earliest embryo and placenta. But these primitive cell types are not gonocytes (i.e., they are not differentiated cells committed to producing sperm or eggs). These tumors are composed of primitive non-germ cells.

So why are the primitive non-germ cell tumors included among the germ cell tumors?

The answer to this question comes from our understanding of the common precancer of most of the seminomatous and non-seminomatous germ cell tumors: intratubular germ cell neoplasia.

In the next several blogs, we'll discuss germ cell precancer, and we'll explain the unifying concept of germ cell neoplasia. We'll also see how a study of precancers is crucial to our understanding of neoplasia, in general.

Jump to Tomorrow's Blog

- © 2010 Jules Berman

key words: carcinogenesis, neoplasia, neoplasms, tumor development, tumour development, germ cell tumor, germ cell tumour, tumor epidemiology, increasing germ cell cancer rates, germ cell cancer, seminomas, seminomatous
In June, 2014, my book, entitled Rare Diseases and Orphan Drugs: Keys to Understanding and Treating the Common Diseases was published by Elsevier. The book builds the argument that our best chance of curing the common diseases will come from studying and curing the rare diseases.

I urge you to read more about my book. There's a generous preview of the book at the Google Books site. If you like the book, please request your librarian to purchase a copy of this book for your library or reading room.