Megumi Hirobe

Long‐term outcome of small, organ‐confined renal cell carcinoma (RCC) is not always favourable

Small, organ‐confined renal cell carcinoma (RCC) generally has favourable pathological characteristics and a good prognosis. However, late recurrence is a known characteristic of the biological behaviour of RCC and no consensus has been established for surveillance protocols from 5 years after radical or partial nephrectomy. In the present study with long‐term follow‐up of patients with small RCCs, 18 of 172 patients (10.5%) with pT1a RCC developed recurrence and eight of these (4.7%) died from cancer. Patients with microvascular invasion had a higher risk for cancer death than those without (P < 0.001, Log‐rank test). Therefore long‐term follow‐up is required after surgery, particularly when the disease has microvascular invasion.

Clinicopathological characteristics of Xp11.2 translocation renal cell carcinoma in adolescents and adults: Diagnosis using immunostaining of transcription factor E3 and fluorescence in situ hybridization analysis

To determine the rate and clinicopathological features of Xp11.2 translocation carcinoma using immunostaining of transcription factor E3 and fluorescence in situ hybridization analysis.

Establishment of an ASPL-TFE3 renal cell carcinoma cell line (S-TFE).

Xp11 translocation renal cell carcinoma is a rare disease diagnosed in children and adolescents in the advanced stage with an aggressive clinical course. Various gene fusions including the transcription factor E3 (TFE3) gene located on chromosome X cause the tumor. We established an Xp11 translocation renal cell carcinoma cell line from a renal tumor in a 18-y-old Japanese female and named it “S-TFE.” The cell line and its xenograft demonstrated definite gene fusion including TFE3. They showed strong nuclear staining for TFE3 in immunohistochemistry, TFE3 gene rearrangement in dual-color, break-apart FISH analysis and ASPL-TFE3 type 1 fusion transcripts detected by RT-PCR and direct DNA sequencing. Although many renal cell carcinoma cell lines have been established and investigated, only a few cell lines are recognized as Xp11.2 translocation carcinoma. S-TFE will be useful to examine the characteristics and drug susceptibility of Xp11 translocation renal cell carcinoma.

Multiple gastrointestinal stromal tumors involving extragastrointestinal sites in neurofibromatosis type 1: Multiple GISTs in NF1

To the Editor: Gastrointestinal stromal tumor (GIST) is a common mesenchymal tumor of the gastrointestinal tract. The histological characteristics of GIST include spindle-shaped and/or epithelioid tumor cells with eosinophilic cytoplasm, which show immunoreactivity for c-kit (CD117), CD34, and DOG1. Some GISTs arise in patients with neurofibromatosis type 1 (NF1). NF1 is a hereditary autosomal dominant disease characterized by caf e-au-lait spots and somatic and visceral neurofibromatosis. NF1 is associated with neoplasms such as neurofibroma, malignant peripheral nerve sheath tumor, glioma, and GIST. NF1-associated GISTs occur at a younger age than sporadic GISTs and multiple tumors often arise in the small intestine, including the duodenum with a tendency towards multiple occurrence. Approximately 5% to 10% of GISTs occur in various sites outside of the gastrointestinal tract. These are known as extragastrointestinal stromal tumors (EGISTs). EGISTs tend to arise in the omentum, retroperitoneum, mesentery, pancreas, gallbladder, liver, spleen, urinary bladder, and prostate. Here, we present a case of a patient with NF1 who had multiple GISTs including an EGIST. Malhotra et al. described the only other case report that we could find of EGIST with NF1. A 55-year-old man with NF1 had gross hematuria and frequent urination for a week. He had a history of intellectual disability and blindness and was treated with holmium laser enucleation of the prostate (HoLEP) for benign prostatic hyperplasia (BPH) 1 year previously. He was found unconscious and taken to the emergency department of Sapporo Medical University Hospital. Computed tomography revealed a low-density 8.9 7.3 cm mass that fully occupied the urinary bladder (Fig. 1a), there was also a low-density 5.0 4.2 cm mass in the duodenum. At surgery, a huge mass seemed to arise from the bladder neck. The mass was surgically excised piece by piece because it was too large to resect en bloc. Subsequently, the mass in the prostatic portion was excised by transurethral resection. Endoscopic ultrasound-guided fine needle biopsy was performed on the duodenal mass 2 weeks after the operation. Macroscopically, the fragments of the bladder mass were solid, elastic, firm, with a grayish-white cut surface. Microscopically, both masses in the urinary bladder and prostatic portion consisted of a fascicular proliferation of spindle-shaped tumor cells with abundant edematous matrix accompanied by diffuse lymphocytic and mast cell infiltration in the entire tumor, and dispersed collagen bands. The bladder tumor was seen proliferating under the urothelium (Fig. 1b) with the tumor cells invading into the muscularis propria of the urinary bladder (Fig. 1c). The tumor cells had ovoid to spindleshaped nuclei with minimal nuclear atypia, and no mitotic figures were observed (0/10 HPF) (Fig. 1d). The cells were diffusely positive for vimentin, c-kit (Fig. 1e), platelet-derived growth factor receptor alpha (PDGFRA; antiPDGFRA rabbit monoclonal antibody D13C6), DOG1, CD34, and aSMA and were focally positive for desmin, HHF35, and cytokeratin AE1/AE3 on immunohistochemistry (IHC). However, IHC for S-100 protein, epithelial membrane antigen, STAT6, progesterone receptor, and ALK was negative. The Ki-67 labeling index (LI) of the tumor cells was less than 1%. The histological and IHC findings, which included positivity for cytokeratin and other smooth muscle markers, suggested a differential diagnosis of inflammatory myofibroblastic tumor (IMT). In addition, we distinguished our case from low-grade malignant peripheral nerve sheath tumor (MPNST), solitary fibrous tumor (SFT), prostatic stromal tumor, and soft tissue perineuroma because of tumor localization and bland spindle cell morphology. Our case was negative for ALK protein that is positive in 50–60% of IMT on IHC. Also, the marble pattern of spindle cell fascicles for low grade MPNST was absent, there were no specialized vascular patterns including stag-horn vasculature for SFT, and STAT6 was negative on IHC. Hypercellular stroma with atypical cells between benign prostatic glands and/or phyllodes pattern for prostatic stromal tumor and reactivity for progesterone receptor were not observed in our case. There were also no epithelial membrane antigen-positive delicate bipolar spindle cells indicative of soft tissue perineurioma. Considering these findings, we finally made a definitive diagnosis of EGIST. We considered that the bladder and prostatic lesions were identical, although we were not able to clarify whether the urinary bladder or prostate was the primary site because the prostate had earlier been excised by HoLEP. Conversely, the duodenal mass was typical of GIST consisting of a fascicular proliferation of bland spindle-shaped tumor cells with mild nuclear atypia and focal nuclear palisading. No mitotic figures were observed (0/10 HPF). The duodenal GIST expressed c-kit,

297 ESTABLISHMENT OF A RENAL CELL CARCINOMA CELL LINE ASSOCIATED WITH TFE3 GENE FUSIONS

INTRODUCTION AND OBJECTIVES: Xp11.2 translocation renal cell carcinoma is a rare disease diagnosed in children and adolescents in the advanced stage with an aggressive clinical course. It has been recently recognized as a subtype of renal cell carcinoma primarily described in the 2004 World Health Organization classification of renal tumors, and various gene fusions including the transcription factor E3 (TFE3) gene located on chromosome cause the tumor; however, little is known about the tumor characteristics. We report the cytogenetic and biological characteristics of a renal cell carcinoma cell line with TFE3 gene fusion established from a young female with locally advanced renal cell carcinoma. METHODS: Tumor cells were obtained from a renal tumor in a 16-year-old Japanese female. This primary tumor was pathologically diagnosed as renal cell carcinoma with Xp11 translocations. After cultured in vitro, cell suspension was inoculated into the nude mice to establish xenograft. TFE3 immunostaining and other immunohistochemistries were performed. Molecular and cytogenetic methods such as RT-PCR, karyotype analysis and FISH were added. RESULTS: The established cell line and its xenograft showed strong nuclear staining for TFE3 in immunohistochemistry, TFE3 gene rearrangement in dual-color, break-apart FISH analysis, and ASPLTFE3 type 1 fusion transcripts detected by RT-PCR and direct DNA sequencing. Multicolor FISH analysis showed more complicated rearrangements on the chromosome than expected. CONCLUSIONS: Although many renal cell carcinoma cell lines have been established and investigated, only a few cell lines are recognized as Xp11.2 translocation carcinoma. This cell line will be useful to examine the characteristics and drug susceptibility of Xp11 translocation renal cell carcinoma.