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muscle spindle - Top 30 Publications

Ectomesenchymal Chondromyxoid Tumor: A Neoplasm Characterized by Recurrent RREB1-MKL2 Fusions.

Ectomesenchymal chondromyxoid tumor is a rare and benign neoplasm with a predilection for the anterior dorsal tongue. Despite morphologic heterogeneity, most cases are characterized by a proliferation of bland spindle cells with a distinctive reticular growth pattern and myxoid stroma. The immunophenotype of these neoplasms is likewise variable; most cases express glial fibrillary acid protein and S100 protein, with inconsistent reports of keratin and myoid marker expression. The molecular pathogenesis is poorly understood; however, a subset of cases has been reported to harbor EWSR1 gene rearrangement. Following identification of an RREB1-MKL2 fusion gene by RNA Sequencing in an index patient, a retrospective review of additional cases of ectomesenchymal chondromyxoid tumors was performed to better characterize the clinical, immunohistochemical, and molecular attributes of this neoplasm. A total of 21 cases were included in this series. A marked predisposition for the dorsal tongue was confirmed. Most cases conformed to prior morphologic descriptions; however, hypercellularity, hyalinized stroma, and necrosis were rare attributes not previously emphasized. The neoplastic cells frequently coexpressed glial fibrillary acid protein, S100 protein, keratin, smooth muscle actin, and/or desmin; a single case was found to contain significant myogenin expression. An RREB1-MKL2 fusion product was identified in 19 tumors (90%), a single tumor (5%) had an EWSR1-CREM fusion product, and the remaining case lacked any known fusion gene by RNA Sequencing. The latter 2 cases subtly differed morphologically from many in the cohort. This series illustrates that recurrent RREB1-MKL2 fusions occur in most, perhaps all, cases of ectomesenchymal chondromyxoid tumor.

Myopericytoma in an unusual location.

Myopericytoma is a soft-tissue tumor of perivascular cells (pericytes). It is slow-growing, usually asymptomatic, and generally benign, although a malignant variant has been described. The etiology is unknown, but it has been associated with local trauma. The most common location is on the distal extremities. Histologically, it is characterized by a well-circumscribed, non-encapsulated proliferation of spindle shaped cells similar to myofibroblasts with oval nuclei and eosinophilic cytoplasm, arranged in perivascular concentric rings. There are few mitoses and no necrosis is reported. The immunohistochemical analysis is positive for smooth muscle actin and negative or weakly positive for desmin. A low Ki-67 proliferation index is typical. Treatment is surgical excision with free margins. Recurrences after adequate excision are uncommon. We describe a 48-year-old woman with a myopericytoma in an unusual location (next to the inner corner of her left eye) who was treated with surgical excision; there has been no recurrence after 5 years of follow up.

Anaplastic lymphoma kinase-negative uterine inflammatory myofibroblastic tumor containing the ETV6-NTRK3 fusion gene: a case report.

Inflammatory myofibroblastic tumors (IMTs) are neoplasms with low malignant potential, and the most common tumor in the lung and orbit. Their occurrence in the uterus is rare. Approximately 50% of IMT patients have anaplastic lymphoma kinase gene ( ALK) rearrangements. Recent studies described novel fusions involving ROS1, platelet-derived growth factor receptor beta ( PDGFR-β), and ETS translocation variant ( ETV6) genes in a subset of ALK-negative patients. We report a 44-year-old woman with anemia and uterine IMT. Ultrasonography and magnetic resonance imaging revealed a myxoid degenerative myoma-like mass, 7.4 cm in maximum diameter, on the left uterine side wall. Hysterectomy was performed as a definitive treatment. Microscopic examination revealed spindle cell proliferation with numerous lymphocytes and plasma cells. Immunohistochemically, the spindle cells were negative for ALK-1, desmin, and smooth muscle actin. The pathological diagnosis was IMT arising from the uterus. Fluorescence in situ hybridization demonstrated an ETV6-neurotrophic tyrosine kinase, receptor, type 3 gene ( NTRK3) translocation but no ALK, ROS1, or PDGFR-β translocations. Lung and abdomen computed tomography at 31 months postoperatively revealed no disease recurrence. This association of an ETV6-NTRK3 fusion oncogene with an ALK-negative uterine IMT increases our understanding of this neoplasm, which may help the development of specific therapies.

Gastrointestinal leiomyoma with interstitial cells of Cajal: mimicker of gastrointestinal stromal tumor.