PMC4515533_01
(a) Computed tomography (CT) demonstrated a large, 15 cm left upper abdominal tumor stemming from the wall of the stomach. Multiple hepatic lesions consistent with metastatic tumor were also identified. (b) Microscopically, scant areas of viable tumor are identified in the patient's GIST (patient after imatinib therapy). (c) Viable tumor was composed of elongated spindle-shaped cells with vesicular chromatin and abundant cytoplasm arranged in fascicles and sheets.
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Four months after the initiation of imatinib therapy, a follow-up CT demonstrated the prior GIST, which had decreased in size to 13.2 x 8.9 x 12.9 cm (Figure 1(a)). The mitotic rate was low, with 0 mitoses identified per 5 mm2 (0-1 mitoses per 10 high power fields) (Figures 1(b) and 1(c)).
(a) Gross image of the nephrectomy specimen shows a 3.6 cm hemorrhagic mass in the lower renal pole. The mass abuts the renal sinus fat. (b) Microscopically, the tumor consists of variably sized nests of cells that are separated by fibrovascular septa. Psammomatous calcifications and focal rounded hyalinized structures are present. (c) Tumor cells have abundant clear to focally eosinophilic granular cytoplasm. (d) The tumor was found to be TFE3 positive.
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The nephrectomy specimen demonstrated a 3.6 x 3.2 x 1.8 cm hemorrhagic mass in the lower renal pole that abutted the renal sinus fat and came within 0.2 cm of the perinephric fat (Figure 2(a)). It consisted of variably sized nests of cells separated by thin, fibrovascular septa (Figure 2(b)). The neoplastic cells were round to polygonal and demonstrated mainly voluminous clear to focally eosinophilic granular cytoplasm, distinct cell membranes, and mildly to moderately atypical vesicular nuclei with occasional nucleoli (Figure 2(c)). They showed strong and diffuse nuclear positivity with transcription factor E3 (TFE3) (Figure 2(d)), and they were negative for cytokeratin AE1/AE3, epithelial membrane antigen (EMA), cytokeratin 7, carbonic anhydrase 9 (CA9), and HMB-45.
This is an unbalanced translocation between Xp and 22q resulting in a loss of Xp and 22p regions shown in (a) complete metaphase and in (b) a partial metaphase.
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Cytogenetic studies performed on fresh tissue from the tumor demonstrated an unbalanced rearrangement characterized by an (X;22) translocation at Xp11.2 and 22p11.1, consistent with an Xp11.2 (TFE3 gene) translocation-associated renal carcinoma (Figure 3).