She died four days postoperatively after gastrectomy and resection of subcutaneous metastasis. Other reports described three patients with subcutaneous metastases in the parietal bone region (15), gluteal region (biopsy

proven and immunohistochemistry positive for CD117) (16), and right upper arm (biopsy proven, immunohistochemistry positive for CD117) (17) respectively. Outside of our article, Inhibitors,research,lifescience,medical the only other literature to report subcutaneous metastasis of GIST and provide both immunohistochemical and mutational analysis of the subcutaneous metastases is a case series by Wang et al (18). They describe two patients with abdominal cutaneous metastases and three extra-abdominal cutaneous metastases (two to scalp and one to cheek). All five cases had multiple concurrent

or subsequent abdominal and/or hepatic metastases. Immunohistochemical studies for CD117 expression Inhibitors,research,lifescience,medical were performed on the cutaneous metastases in all five cases, and all cases were positive for CD117. In addition to this, four out of the five cases were analyzed for KIT mutations in exons 9, Inhibitors,research,lifescience,medical 11, 13, and 17. Two of the four cases had mutations in exon 11, and the remaining two cases were wild-type for exons 9, 11, 13, and 17. Discussion The development of molecularly targeted therapy against c-KIT and PDGFRA with imatinib and sunitinib has significantly altered the GX15-070 cell line treatment of GIST. Notably, imatinib has been shown to increase progression free survival in advanced disease (19). Most of the somatic mutations in Inhibitors,research,lifescience,medical c-KIT are gain-of-function mutations found in exon 11 and exon 9, with exon 11 mutations showing improved objective responses,

time to tumor progression, and overall survival in patients treated with imatinib (19). A mutation in exon 11 was present in our patient’s malignancy, and she experienced a time to tumor progression of approximately two years while on imatinib. With progression to liver metastases, indicating Inhibitors,research,lifescience,medical imatinib resistant GIST, she was started on sunitinib. Despite use of sunitinib, her disease progressed in the form of lung and bone metastases. The clinical activity of sunitinib after imatinib failure has also been correlated with kinase genotype, with progression-free survival and overall survival significantly longer for patients with primary KIT exon 9 mutations or with wild-type genotype, as Histamine H2 receptor compared to those with KIT exon 11 mutations (20). While the relationship between certain kinase genotypes and clinical progression has been described in articles by Heinrich et al (19),(20), it remains unclear why some patients develop particularly aggressive and unusual metastases. It is also unclear why expression of CD117 in certain metastatic lesions is diminished or absent, such as in our patient’s left arm subcutaneous nodule. The absence of CD117 may be related to dedifferentiation of the malignancy or associated with changes induced by tyrosine kinase inhibitor therapy.