Testicular Cancer & Marijuana Use

From a recent abstract:

BACKGROUND:
Testicular germ cell tumor (TGCT) incidence increased steadily in recent decades, but causes remain elusive. Germ cell function may be influenced by cannabinoids, and 2 prior epidemiologic studies reported that the use of marijuana may be associated with nonseminomatous TGCT. Here, the authors evaluate the relation between TGCTs and exposure to marijuana and other recreational drugs using a population-based case-control study.
METHODS:
In total, 163 patients who were diagnosed with TGCT in Los Angeles County from December 1986 to April 1991 were enrolled, and 292 controls were matched on age, race/ethnicity, and neighborhood. Participants were asked about drug use by a structured, in-person interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression analysis adjusted for history of cryptorchidism; education; religiosity; and reported use of marijuana, cocaine, and amyl nitrite.
RESULTS:
Compared with never use, ever use of marijuana had a 2-fold increased risk (OR, 1.94; 95% CI, 1.02-3.68), whereas ever use of cocaine had a negative association with TGCT (OR, 0.54; 95% CI, 0.32-0.91). Stratification on tumor histology revealed a specific association of marijuana use with nonseminoma and mixed histology tumors (OR, 2.42; 95% CI, 1.08-5.42).
CONCLUSIONS:
A specific association was observed between marijuana use and the risk of nonseminoma and mixed tumors. To the authors' knowledge, this is the first report of a negative association between cocaine use and TGCT risk. The current results warrant mechanistic studies of marijuana's effect on the endocannabinoid system and TGCT risk and caution that recreational and therapeutic use of cannabinoids by young men may confer malignant potential to testicular germ cells. Cancer 2012. © 2012 American Cancer Society.

What the heck, you didn't need them anyway.

The evidence of whether marijuana smoking causes lung cancer seems to be somewhat mixed, with some studies finding evidence that it does (and this really should not be a surprise if it does), and others finding no evidence for it.  Here is a recent longitudinal study indicating that there is reason for concern:

As the paper explains, some case-control studies do not show a reason for concern, while others do show an association.  Especially in light of the very similar nature of marijuana smoke and tobacco smoke, and that pot smokers do not just inhale, but hold it in their lungs, it would be a bit surprising if there was not an association.