Second Report of PDE10A-BRAF Fusion in Pediatric Spindle Cell Sarcoma With Infantile Fibrosarcoma-Like Morphology Suggesting PDE10A-BRAF Fusion Is a Recurrent Event

Infantile/congenital fibrosarcoma (IFS) is the most common soft tissue tumor in children less than one year of age. The most common anatomic site of IFS is in the extremities or trunk, and rarely in the abdomen or retroperitoneum. Approximately 70-90% of cases are characterized by a distinct t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. As such, TRK inhibitors are considered frontline therapy in TRK-fusion positive IFS. The ETV6-NTRK3 fusion is also detected in congenital mesoblastic nephroma (CMN) and less frequently in myeloid leukemias, secretory breast carcinoma, and mammary-type secretory carcinoma of the skin and salivary glands. Infrequently, cases of tumors with IFS-like morphology without the characteristic ETV6-NTRK3 gene fusion have been identified. Herein, an ETV6-NTRK3 fusion negative spindle cell sarcoma with IFS-like morphology subjected to genomic profiling revealed a PDE10A-BRAF fusion, a fusion event that has been detected previously in an isolated case of undifferentiated infantile sarcoma.

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A Case Report Of A Spindle Cell Sarcoma With Ntrk-3 Rearrangement And A Novel Gene Fusion Partner (Ntrk3-Eif2s2)

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqaa161.151 ◽

2020 ◽

Vol 154 (Supplement_1) ◽

pp. S69-S70

Author(s):

A Shalaby ◽

A Alhussain ◽

Y Al Hmada ◽

A Bernieh

Keyword(s):

Gene Fusion ◽

Spindle Cell ◽

Fusion Gene ◽

Spindle Cell Sarcoma ◽

Fusion Partner ◽

Nerve Sheath Tumor ◽

Sequencing Analysis ◽

Cell Sarcoma ◽

Infantile Fibrosarcoma ◽

Spindle Cells

Abstract Casestudy A group of spindle cell tumors with characteristic morphologic features, co-expression of CD34 and S100 and recurrent gene rearrangements in RAF-1, BRAF, and NTRK has recently been described. These tumors were found to be previously labeled as malignant peripheral nerve sheath tumor, infantile fibrosarcoma or unclassified spindle cell sarcoma. We describe a case of a 25-year-old female who presented with a right thigh mass. She underwent an ultrasound-guided biopsy showing a spindle cell tumor with co-expression of CD34 and S100 and subsequently underwent resection of the mass. Gross examination showed a 7.5 cm multi-lobulated, tan-pink, hemorrhagic and fleshy mass. Histologically, the tumor was relatively well-demarcated and consisted of spindle cells with moderate to high cellularity in a patternless architecture. The spindle cells showed moderate to marked pleomorphism, pale amphophilic cytoplasm, ovoid-to-elongated nuclei with vesicular chromatin, and occasional prominent nucleoli. Areas of prominent perivascular and stromal hyalinization were seen. Mitotic activity was brisk with up to 33 mitoses per 10 high power fields. Necrosis representing approximately 5% of the mass was identified. On immunohistochemistry, the tumor cells showed strong and diffuse positivity for CD34 and S100 and were negative for SOX10, broad-spectrum cytokeratin, EMA, SMA, Desmin, STAT6, MUC4, TLE1, and H3K27me3 (retained nuclear expression). EIF2S2-NTRK3 fusion gene was detected using next generation sequencing analysis. Conclusion A few cases of NTRK3 spindle cell sarcomas, other than classic infantile fibrosarcoma, have been previously reported in the literature with fusion genes involving ETV6, EML4, and STRN, among others. A gene fusion involving NTRK3 and EIF2S2 has not been previously reported. NTRK3-fused sarcomas typically show high-grade morphology and aggressive clinical behavior. Identification of NTRK-fused sarcomas is clinically important, as these advanced tumors are potentially amenable to NTRK inhibition. In our case, patient received adjuvant post-operative radiation therapy and returned with lung metastasis 5 months after surgery.

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Ultrastructure of mesotheliomas

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110775 ◽

1984 ◽

Vol 42 ◽

pp. 98-101

Author(s):

Irving Dardick

Keyword(s):

Electron Microscopy ◽

Latent Period ◽

Spindle Cell ◽

Spindle Cell Sarcoma ◽

Metastatic Adenocarcinoma ◽

Cell Sarcoma ◽

Cytological Features ◽

Industrial Use ◽

Degree Of Differentiation

With the extensive industrial use of asbestos in this century and the long latent period (20-50 years) between exposure and tumor presentation, the incidence of malignant mesothelioma is now increasing. Thus, surgical pathologists are more frequently faced with the dilemma of differentiating mesothelioma from metastatic adenocarcinoma and spindle-cell sarcoma involving serosal surfaces. Electron microscopy is amodality useful in clarifying this problem.In utilizing ultrastructural features in the diagnosis of mesothelioma, it is essential to appreciate that the classification of this tumor reflects a variety of morphologic forms of differing biologic behavior (Table 1). Furthermore, with the variable histology and degree of differentiation in mesotheliomas it might be expected that the ultrastructure of such tumors also reflects a range of cytological features. Such is the case.

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