This study will collaborate with the below study of Dr. van de Rijn at Stanford. In many patients with desmoid-type fibromatosis (DTF), the tumors recur after surgical excision. A major problem confronting clinicians who treat DTF is the lack of well-established criteria that predict which tumors will recur. Treating physicians do not know which patients are at high risk, and they are sometimes unsure about how aggressively to treat an individual patient. Recently, researchers have suggested that specific genetic mutations in the gene encoding β catenin predict a greater risk of tumor recurrence. While β catenin mutations seem to be useful prognostic markers, it is hypothesized that there are other so-called “driver mutations” that contribute to aggressive behavior in DTF. Therefore, Dr. Cates proposes to sequence the entire coding region of genomic DNA in DTF and adjacent normal tissues to identify additional DNA mutations in these tumors. To discover somatic mutations that predict tumor recurrence, he will also compare cases of DTF that recurred to similar cases that did not recur. Identification of mutations associated with an increased risk of local recurrence might assist doctors and patients faced with difficult management decisions and lead to discovery of potential drug targets.