[Imaging and pathological features of gastrointestinal stromal tumors].

OBJECTIVE: To investigate the imaging features and pathological manifestations of gastrointestinal stromal tumors (GISTs). METHODS: The imaging characteristics and pathological manifestations of 26 surgically treated patients with histologically confirmed GISTs were retrospectively analyzed. RESULTS: The tumors were found to originate from the small bowel (n=10), stomach (n=8), colon (n=6), mesentery (n=1) and omentum (n=1). The imaging and pathological features of GISTs were (1) most of GISTs were well-defined and exophytic (n=19, 73.1% ), which usually compressed the adjacent tissues but no invasion. The tumor diameter ranged from 5.1 to 23.5 cm with a mean diameter of 11.6 +/- 5.9 cm, (2)most tumors had an inhomogenous density or signal intensity due to necrosis(n=21, 80.8%), hemorrhage (n=15, 57.7%) or calcification (n=3, 11.5%) within the tumor, (3) on the CT or MR images, heterogeneous enhancement pattern presented as peripheral or intra-tumor patchy enhancement was common (n=21, 80.8%). Furthermore, enhanced striped vessels were seen in 12 patients. However, homogenous enhancement pattern was rare (n=5, 19.2%), (4) the most common site where GIST metastasized to was the liver (n=7), followed by the peritoneum (n=4), but rarely to lymph nodes, (5) of these 26 patients, spindle-cell type was observed in 69.2% (n=18), epithelioid-cell type in 23.1% (n=6), and mixed cell type in 7.7% (n=2). Immunohistochemical studies showed positive CD117 expression in all of these 26 patients, but positive CD34 expression in only 22 patients. CONCLUSION: Gastrointestinal stromal tumor usually presents as a exophytic, well-defined large tumor, with internal striped vessels, necrosis or hemorrhage within. It usually metastasizes to the liver or the peritoneum but rarely to lymph nodes. Pathologically, most of gastrointestinal stromal tumors consist of spindle-cells, while a small portion of the tumors are composed of epithelioid-cells or mixed ones. Both CT and MRI play an important role in the diagnosis of gastrointestinal stromal tumors.

Retroperitoneal liposarcoma: MR characteristics and pathological correlative analysis.

BACKGROUND: Liposarcoma is the most common primary retroperitoneal malignant neoplasm. However, preoperative diagnosis is a common problem due to lack of characteristic clinical presentations. It has been assumed that MRI, based on its high soft-tissue resolution, could discover and discern different subtypes of this tumor. Moreover, there has been little in the literature to compare the MRI features with pathological appearances of the retroperitoneal liposarcomas. METHODS: We retrospectively analyzed 19 cases of retroperitoneal liposarcoma (11 males and 8 females, aged 41-79 years) proved surgically and histologically. All patients underwent MRI examination before and after the administration of contrast agent. The MRI features and postoperative pathological appearances were studied correlatively. RESULTS: Nine cases were located in the anterior pararenal space, four cases in the posterior pararenal space and six cases in the perirenal space. Among all cases, ten cases were present in the right retroperitoneum and nine cases in the left. The average diameter of the tumors was 14.7 cm (range from 7.5 cm to 26 cm). The MR signal intensity of liposarcoma was heterogeneous and varied greatly, depending on the components of the tumor and the different histological patterns. There are five subtypes of retroperitoneal liposarcoma. Myxoid liposarcoma (n = 7) exhibited low signal intensity on T1W image and high signal intensity on T2W image. On histologic analysis, myxoid liposarcoma consists of a myxoid matrix as the predominant component and small amounts of mature fat. Enhanced solid tissues and thickened septa of myxoid liposarcoma were seen on post-contrast image. Well-differentiated liposarcoma (n = 5) presented in high signal intensity on T1W images, intermediate signal intensity on T2W images, drop-out signal intensity on fat-suppressed MR images; The enhanced tenuous septa and solid tissues were seen on post-contrast image. Round-cell liposarcoma (n = 2) and pleomorphic liposarcoma (n = 2) exhibited soft-tissue tumor signal intensity without characteristic fat signal. One case of round-cell liposarcoma appeared with intratumoral hemorrhage and invaded the inferior vena cava. Dedifferentiated liposarcoma (n = 3) exhibited small amounts of fatty components with a clear demarcation between fat and nonadipose solid tissue on MR images. One case of dedifferentiated liposarcoma invaded the kidney. CONCLUSION: MRI can clearly demonstrate shape, margin, internal components and surrounding tissues. Different subtypes of retroperitoneal liposarcoma exhibited varying MRI features, depending on tumor histological components. MRI should be an ideal method for diagnosing retroperitoneal liposarcoma.