Pediatric soft tissue tumor of the upper arm with LMNA-NTRK1 fusion

Publication date: Available online 26 August 2017
Source:Human Pathology
Author(s): Shinji Kohsaka, Tsuyoshi Saito, Keisuke Akaike, Yoshiyuki Suehara, Takuo Hayashi, Tatsuya Takagi, Kazuo Kaneko, Toshihide Ueno, Shinya Kojima, Ken-ichi Kohashi, Hiroyuki Mano, Yoshinao Oda, Takashi Yao
A 6-year-old girl was admitted to our hospital due to the presence of a slow-growing tumor in her right elbow. Biopsy specimens showed a round- to spindle-cell neoplasm with uncertain malignant potential, leading to the decision of surgical resection. Histologically, the resected tumor was encapsulated by fibrous tissue, but focally invaded the surrounding skeletal muscles. The tumor was composed of ganglion-cell-like short spindle cells with lymphocytic infiltration in the collagenous background. Tumor cells with large bizarre nuclei were occasionally observed, and multinucleated giant cells were scattered at the periphery. Hemangiopericytoma-like patterns and adipose tissue elements were not evident, and mitotic figures were rarely observed (<1 per 10 high-power fields). Immunohistochemically, the tumor cells were positive for S-100 and CD34 and focally positive for EMA and AE1/AE3. RNA sequencing and subsequent RT-PCR revealed alternative splicing forms of LMNA-NTRK1 fusion (Ex2-Ex10 and Ex2-Ex15).



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