Insights From: Victor Villalobos, MD, PhD, University of Colorado School of Medicine; Saketh Guntupalli, MD, University of Colorado School of Medicine; Shreyaskumar R. Patel, MD, University of Texas MD Anderson Cancer Center; Anthony P. Conley, MD, University of Texas MD Anderson Cancer Center
Shreyaskumar R. Patel, MD: Soft tissue sarcomas are a very rare group of tumors. As a group of diseases, the annual incidence appears to be about 12,300 cases. When you compare it to the common epithelial tumors, like breast cancer, lung cancer, colon cancer, and prostate cancer, the incidences are more than ten-fold different. This is made even more complex by the fact that it’s not 1 disease. It’s a group of diseases. There could be 50 plus subtypes, or 70 plus subtypes of soft tissue sarcomas. Luckily, in the clinics, there are a few that we encounter far more commonly than others. The top 3 soft tissue sarcoma histologies would be liposarcoma, leiomyosarcoma, and undifferentiated pleomorphic sarcoma, which, in older days, used to be called malignant fibrous histiocytoma.
Then, there’s a smattering of several other histologies that will happen in variable frequency. In terms of incidence and the distribution in terms of age limit, this is an interesting disease that spans from the pediatric age group all the way to octogenarians and nonagenarians, if you will. Young children develop these same diseases, and older people develop the diseases. There may be some histologic predilection for it. For example, the pediatric soft tissue sarcomas tend to be more of the osteosarcomas, Ewing’s sarcomas, rhabdomyosarcomas and the occasional synovial sarcoma, as opposed to the adult population where we talk about liposarcomas, leiomyosarcomas and undifferentiated pleomorphic sarcomas.
Within soft tissue sarcoma, there is a broad way of classifying or subcategorizing them. About 60% to 65% of all soft tissue sarcomas will arise in the extremities. Within extremities, lower extremity is more common than upper extremity. The remainder, about 30% of them, will arise in the trunk and the intra-abdominal, what we call, retroperitoneal locations. That leaves you with approximately 10% of cases that would arise in the head and neck area, or could arise from visceral organs. That’s the broad way of distinguishing or subcategorizing where these originate from.
The implication of this, in terms of biology and surgical abilities, and how well the surgeons can get around it, and, to a certain extent, from a clinical behavior standpoint, the metastatic pattern may also be somewhat driven by the anatomic location. For example, a generic comment that always gets me is that sarcomas have a predilection to spread to the lungs. They have a lung-dominant metastatic pattern. That’s a true statement. The exceptions would be some of the intra-abdominal sarcomas, given their location and how the venous drainage works out. Liver metastases may be far more common in an intra-abdominal sarcoma than it would be in an extremity sarcoma, for example. So, there can be some specific clinical behavior issues that may relate to the actual site of origin.
The location of the tumor also has some bearing, in terms of when the patient presents to the physician. Clearly, if there was a growing lump on the back of someone’s hand or on their leg, they’re far more likely to pick it up early. It draws their attention. They may go to their primary care physician, get it worked up, and you may pick up an extremity sarcoma earlier than a typical intra-abdominal primary tumor. By virtue of its anatomic location, the tumor has plenty of room to grow until it gets big enough to put some pressure on the surrounding visceral organs or nerve plexuses to create some symptoms.
As a general rule, it wouldn’t be unheard of for the intra-abdominal sarcomas to be routinely large. Whereas, extremity sarcomas can span from small to large, depending on their location, and how quickly the patient has received and figured it out.