Monday, September 27, 2010

Non-seminomatous germ cell tumors

In yesterday's blog, we examined the enormous increase in the incidence of seminomatous germ cell tumors occurring in white non-Hispanic males.

There are two categories of germ cell tumors: seminomatous and non-seminomatous.

The seminomatous tumors are tumors composed predominantly of a single cell type, the gonocyte. The non-neoplastic gonocyte would normally produce sperm cell in the testis. Seminomas are permitted to contain a few neoplastic trophoblasts, but otherwise, seminomas are composed of a population of large, round, monomorphic cells.

The other type of germ cell tumors is the non-seminomatous tumors, and these tumors are composed of malignant cells resembling those of the pluripotent primitive embryonic (from the early embryo) or extra-embryonic (from the placenta) malignant cells. Consequently, the non-seminomatous germ cell tumors may be teratomatous, primative embryonic, choriocarcinomatous, or some mixture of these. Non-seminomatous germ cell tumors may even contain foci of seminoma! The key characteristic of non-seminomatous germ cell tumors of the testis is that they must have a component of primitive neoplastic cells that are not seminoma cells.

Can we observe the same increased incidence of non-seminomatous germ cell tumors as we saw (yesterday) in the seminomatous germ cell tumors.

NO. Here are the numbers, computed from the SEER (the U.S. National Cancer Institute's Surveillance Epidemiology and End Results) public use data files. The first column is the crude number of occurrences of non-seminomatous germ cell tumors of testes in white, non-Hispanic males. The second column is the number of occurrences expressed as a proportion of all of the seer cases for the year examined, and the third column is the number of occurrences expressed as a proportion of the U.S. population for the year examined.


crude of SEER of U.S. Pop
1973 000109 000196 000051
1974 000147 000218 000068
1975 000157 000213 000072
1976 000165 000218 000075
1977 000189 000246 000085
1978 000167 000214 000075
1979 000182 000226 000080
1980 000216 000260 000095
1981 000222 000259 000096
1982 000203 000234 000087
1983 000226 000251 000096
1984 000219 000234 000092
1985 000238 000243 000100
1986 000233 000232 000097
1987 000253 000238 000104
1988 000222 000206 000090
1989 000263 000238 000106
1990 000243 000209 000097
1991 000237 000192 000094
1992 000237 000185 000092
1993 000245 000194 000095
1994 000222 000176 000085
1995 000216 000169 000082
1996 000247 000202 000093
1997 000225 000178 000084
1998 000234 000180 000086
1999 000245 000185 000089
2000 000237 000177 000084
2001 000223 000162 000078
2002 000258 000185 000089
2003 000230 000166 000079
2004 000278 000192 000094
2005 000275 000188 000092
2006 000251 000169 000084
2007 000277 000182 000091

Here's the graph. The blue columns are the crude occurrences. The maroon columns are the numbers as a proportion of the year's seer records, and the white column are the numbers as a porportion of the U.S. population in the examined year.



There's a small increase since 1973, but much of the increase is accounted for by the increase in the SEER population and the increase in the U.S. population for the same years. The relative (population adjusted) rate of occurrence of non-seminomatous germ cell tumors has not increased by much; certainly nothing like the increase seen yesterday, for the seminomatous germ cell tumors.

What about the germ cell tumors that occur outside the gonads? Are they increasing in occurrence since 1973? Though germ cell tumors can occur outside the gonads, they are very rare. Here are the SEER numbers for non-seminomatous non-testicular germ cell tumors in white non-Hispanic males.


crude of SEER of U.S. Pop
1973 000011 000019 000005
1974 000008 000011 000003
1975 000014 000019 000006
1976 000011 000014 000005
1977 000011 000014 000004
1978 000011 000014 000004
1979 000019 000023 000008
1980 000021 000025 000009
1981 000016 000018 000006
1982 000019 000021 000008
1983 000018 000020 000007
1984 000012 000012 000005
1985 000019 000019 000007
1986 000014 000013 000005
1987 000025 000023 000010
1988 000016 000014 000006
1989 000020 000018 000008
1990 000011 000009 000004
1991 000023 000018 000009
1992 000011 000008 000004
1993 000018 000014 000006
1994 000012 000009 000004
1995 000010 000007 000003
1996 000009 000007 000003
1997 000018 000014 000006
1998 000010 000007 000003
1999 000013 000009 000004
2000 000005 000003 000001
2001 000015 000010 000005
2002 000013 000009 000004
2003 000010 000007 000003
2004 000017 000011 000005
2005 000020 000013 000006
2006 000011 000007 000003
2007 000012 000007 000003

Here are the numbers for seminomatous non-testicular germ cell tumors in white non-Hispanic males.

crude of SEER of U.S. Pop
1973 000002 000003 000000
1974 000001 000001 000000
1975 000005 000006 000002
1976 000004 000005 000001
1977 000010 000013 000004
1978 000008 000010 000003
1979 000004 000004 000001
1980 000014 000016 000006
1981 000016 000018 000006
1982 000011 000012 000004
1983 000011 000012 000004
1984 000011 000011 000004
1985 000013 000013 000005
1986 000016 000015 000006
1987 000014 000013 000005
1988 000011 000010 000004
1989 000016 000014 000006
1990 000010 000008 000004
1991 000011 000008 000004
1992 000014 000010 000005
1993 000013 000010 000005
1994 000023 000018 000008
1995 000017 000013 000006
1996 000020 000016 000007
1997 000018 000014 000006
1998 000010 000007 000003
1999 000009 000006 000003
2000 000016 000012 000005
2001 000014 000010 000004
2002 000017 000012 000005
2003 000016 000011 000005
2004 000022 000015 000007
2005 000026 000017 000008
2006 000014 000009 000004
2007 000017 000011 000005

Non-testicular germ cell tumors represent a tiny fraction of the germ cell tumors occurring in men. For the purposes of analysis, there's not much you can do with these tumors. They're not going to give you statistically significant results when you try to test a hypothesis; some of them may represent misdiagnoses (e.g., colon cancer mistaken for monomorphic teratoma in a peri-testicular appendage), or a conservative topographic assignment (peri-testicular metastasis from a regressed primary germ cell tumor).

So, for the purposes of this blog, where we're trying to find a biological explanation for the rise in seminomas in non-Hispanic white males, we'll ignore the non-testicular germ cell tumors.

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