Exceptions to every rule

Speaking with my mother about cancer the other day, I told her that cancers rarely metastasize to the spleen.  In fact I have never seen it nor had I even heard of it.  Not more than 2 days later was an interesting case presented at one of our conferences.  A CT scan showed a large tumor growing out of the left side of the pancreas (known as the "tail"), and into the spleen.  There also appeared to be what were isolated nodules in the spleen which might have been metastases.

The surgeons suspected that the cancer was a pancreatic adenocarcinoma, so they removed the left half of the patient's pancreas and spleen (which is a pretty standard operation, a "distal pancreatectomy and splenectomy").  In the operating room however the surgeons noticed that the mass was softer, and did not feel fibrotic like how they might expect a pancreatic adenocarcinoma to feel.

Actually, it turns out the tumor was not a pancreatic adenocarcinoma; it was a diffuse large B cell lymphoma.  In retrospect, that might have been higher on the differential diagnosis.  It is indeed very rare for a GI-derived adenocarcinoma to metastasize to the spleen.  Adenocarcinomas are cancers that are derived from cells that line the surfaces of the body, and the GI tract is actually a surface if you think about it - it is exposed to the outside elements.  After all, the GI tract is just a long tube running through the body; the lumen of the tube isn't actually IN the body.

 Alternatively, lymphomas are cancers that are derived from lymphoid-lineage hematopoietic cells, which is a scientific way of saying white blood cells.  The spleen is a major lymphoid organ in the body, and lots of white blood cells end up there to be "trained" to respond to infectious pathogens.  Think of the spleen as a gymnasium for your immune system.  In retrospect, it isn't so surprising that a large tumor invading and "metastasizing" to the spleen actually turned out to be a lymphoma, instead of a carcinoma.  So what I told my mother is only true with a qualifier:  it is extremely rare for [a cancer] an adenocarcinoma of GI origin to metastasize to the spleen.

You might be wondering, if the spleen is so important for your immune system, how can we take it out without pause?  Patients with splenectomy by and large retain immune function, but they are actually more vulnerable to specific types of bacterial infection.  Especially bacteria which have capsules can pose a challenge to a patient without a spleen, as encapsulated organisms require a very specific and focused immune response to defeat, the sort of which requires splenic function.  To compensate, we can vaccinate patients who are going to get a splenectomy for the most common encapsulated infectious organisms:  streptococcus pneumoniae, neisseria meningitidis, and haemophilus influenzae.  Patients without a spleen do not have any problem leading a normal life.

Update - Hepatopancreaticobiliary.

For my first month at Memorial, I was on the HPB service, the focus of which is liver and pancreas.  Rotating on HPB as a student is a very good learning experience because it is one of the more extreme areas of oncology.  The surgical cases in HPB tend to be on the longer side.  The pancreas in particular, while being a relatively small organ, is notoriously hard to get to.  It also shares blood supply with other organs.  The end result is that operations involving the pancreas tend to be long and complex, and usually include removing other organs as well (the duodenum on one end, the spleen on the other).

The classic pancreas operation is the "whipple procedure" which takes 4-8 hours depending on the patient.  Surgeons perform a whipple if there is a tumor in the head of the pancreas.  The duodenum also must come out, since the head of the pancreas and the duodenum share a common blood supply.  The problem with taking out the duodenum is that it connects the stomach to the rest of the small intestine, and it also is where the bile from the liver and pancreatic juices drain into.  So once the duodenum is removed, the stomach must be joined to the rest of the small intestine, and the plumbing from the liver and the remnant of the pancreas must also be re-attached.

Other times we do a "distal pancreatectomy", most commonly for small lesions in the tail of the pancreas (more to the left) which can be pre-cancerous (IPMN).  Distal pancreatectomies are not easy either, and since the splenic artery runs right under the pancreas they often involve splenectomy as well.

The liver is also a major component of HPB surgical oncology.  We do surgery on the liver if there is a primary liver tumor (that is, the cancer started in the liver) or there are metastases to the liver.  The liver is where nutrients from digestion are processed by the body.  When we eat or drink, the nutrients, toxins, vitamins, and water are absorbed in the stomach, intestine, colon.  Those organs then immediately drain into the liver in what is called the "hepatic portal vein".  That is why a cancer that originates in the GI tract is so likely to spread to the liver.  Not all veins in the lower body drain immediately to the liver, however.  Some of them skip the liver and go right to the lungs.  That is why cancer so commonly spreads to the liver and lungs.

Anyway, so on HPB we see patients with colon cancer who have metastases in the liver.  A general rule of cancer is that the presence of distant metastases generally means the cancer cannot be cured by surgery, but there are exceptions to this rule, and colon cancer is one of them.  If a patient has a colon cancer removed, and then a year later they have a liver tumor, we often will try to take out that liver tumor.  Liver surgery is challenging because the organ is so vital, and variable.  The surgeon must be very aware of the anatomy and ready to avoid major bleeding, but without compromising other major vessels.  Liver surgery can turn catastrophic really quickly without extra caution.

In the hands of an experienced surgeon, liver surgery is very safe.  Additionally, the organ is the only in the body that is capable of regenerating, so you can remove a huge chunk of a patient's liver and the rest will grow right back.  My attending on HPB is working on a project with some engineers that maps the internal blood networks of a patient's liver before hand.  Then during the case, the engineers use lasers to scan the outside and contours of the liver and they match the internal blood network to the real-time layout of the liver.  When the project is perfected, a surgeon should be able to take a probe and point it to any spot on the patient's liver and look at a real-time 3-dimensional screen to see where the blood vessels below are running.  Right now we can get some idea with ultrasound (so don't worry, the surgeon's are not flying blind), but this would be a big improvement.

The other reason why HPB is a good service for students in oncology is that we are exposed to the less rosy side of surgical oncology.  In HPB we commonly see pancreatic adenocarcinoma, cholangiocarcinoma, and hepatocellular carcinoma.  All of these cancers carry a very poor prognosis.  Even with complete surgical resection, negative lymph nodes, and negative margins, these cancers more likely than not will come back, and quickly.

I finished HPB last week and now I have started my second rotation, GMT (gastric and mixed tumors), which include sarcoma and melanoma.  This month I am seeing a great diversity of very rare cancers and learning more about melanoma (which is not so rare).  I'll update about that soon.

Funny!

The Onion is an online political satire site.  They have a hilarious piece on New York City.  Lots of profanity, but I wouldn't have it any other way.

Banksy!

I know this is totally not the update that people are looking for.  Last night, Sarah, David and I went to Williamsburg for dinner at this awesome BBQ place.  Williamsburg is an upcoming area right outside of Manhattan (one subway stop under the East River) where property values will be quadrupling over the next ten years.  Its kind of a rugged, artsy area that has a very unique feel even for NYC.

Anyway, we were walking into a neat looking Tea Bar and I noticed a piece of graffiti.  I recognized it as the work (or an amazingly good imitation) of a world famous graffiti artist by the name of Banksy.  In this graffiti there is a man holding a remote control.  You look to his right and there is a giraffe with a receiver collar around its neck, implying that the man is driving the giraffe.  And in the giraffe's mouth is a paintbrush, which it is using to write "vandal" on a high spot on the wall.  Very cool!