Myoepithelial tumors of soft tissue and bone in children and young adults: A clinicopathologic study of 40 cases occurring in patients ≤ 21 Years of age.

Myoepithelial tumors of the soft tissue and bone occurring in patients 21 years of age and younger are rare, and their clinicopathologic features remain incompletely understood. We studied a well-characterized series of 40 such tumors. Cases were retrieved from our archives for the period 2009-2022 and re-reviewed. Available immunohistochemical and molecular genetic data was collected. Clinical information including available follow-up was obtained. The tumors occurred in 18 males and 22 females, ranging from 3 months to 21 years of age (median 11.5 years), and involved a wide variety of soft tissue (n = 36) and bone (n = 4) locations. Histologically benign myoepithelial tumors tended to occur in adolescents (median age 14.5 years; range 5-21 years), whereas myoepithelial carcinomas occurred in younger patients (median age 8.5 years; range 3 months-20 years). Microscopically, the tumors showed a complex admixture of epithelioid, plasmacytoid and spindled cells in a variably hyalinized, myxoid, chondroid or chondromyxoid background. Small subsets of histologically malignant tumors had rhabdoid or "round cell" features. Immunohistochemistry showed 35/40 (88%) cases to be positive with at least one keratin antibody. The 5 keratin-negative tumors were uniformly positive for S100 protein and/or SOX10 and expressed EMA (4 cases) and/or p63 (3 cases). EMA, SMA and GFAP were positive in 21/25 (84%), 13/21 (62%), and 8/21 (38%) tumors, respectively. SMARCB1 and SMARCA4 expression was retained in 29/31 (94%) and 22/22 (100%) of cases, respectively. FISH for EWSR1 gene rearrangement was positive in 6/18 (33%) tested cases. Two EWSR1-negative tumors were also FUS-negative. NGS identified EWSR1::POU5F1, FUS::KLF17, and BRD4::CITED1 gene fusions in 3 tested cases. Clinical follow-up (22 patients; median 23 months; range 1-119 months) showed 3 patients with local recurrences and 5 with distant metastases (lymph nodes, lung, and brain). Three patients died of disease, 3 were alive with recurrent or unresectable disease, and 16 were disease-free. Adverse clinical outcomes were seen only in patients with malignant tumors. We conclude that myoepithelial neoplasms of soft tissue and bone are over-repesented in patients ≤21 years of age, more often histologically malignant, and potentially lethal. Histologic evaluation appears to reliably predict the behavior of these rare tumors.

Outcomes in ovarian Sertoli-Leydig cell tumor: A report from the International Pleuropulmonary Blastoma/DICER1 and Ovarian and Testicular Stromal Tumor Registries.

OBJECTIVE: Sertoli-Leydig cell tumors (SLCTs) are rare sex cord-stromal tumors, representing <0.5% of all ovarian tumors. We sought to describe prognostic factors, treatment and outcomes for individuals with ovarian SLCT. METHODS: Individuals with SLCT were enrolled in the International Pleuropulmonary Blastoma/DICER1 Registry and/or the International Ovarian and Testicular Stromal Tumor Registry. Medical records were systematically abstracted, and pathology was centrally reviewed when available. RESULTS: In total, 191 participants with ovarian SLCT enrolled, with most (92%, 175/191) presenting with FIGO stage I disease. Germline DICER1 results were available for 156 patients; of these 58% had a pathogenic or likely pathogenic germline variant. Somatic (tumor) DICER1 testing showed RNase IIIb hotspot variants in 97% (88/91) of intermediately and poorly differentiated tumors. Adjuvant chemotherapy was administered in 40% (77/191) of cases, and among these, nearly all patients received platinum-based regimens (95%, 73/77), and 30% (23/77) received regimens that included an alkylating agent. Three-year recurrence-free survival for patients with stage IA tumors was 93.6% (95% CI: 88.2-99.3%) compared to 67.1% (95% CI: 55.2-81.6%) for all stage IC and 60.6% (95% CI: 40.3-91.0%) for stage II-IV (p < .001) tumors. Among patients with FIGO stage I tumors, those with mesenchymal heterologous elements treated with surgery alone were at higher risk for recurrence (HR: 74.18, 95% CI: 17.99-305.85). CONCLUSION: Most individuals with SLCT fare well, though specific risk factors such as mesenchymal heterologous elements are associated with poor prognosis. We also highlight the role of DICER1 surveillance in early detection of SLCT, facilitating stage IA resection.

Getting Your Laboratory on Track With Neurotrophic Receptor Tyrosine Kinase.

CONTEXT.­: Neurotrophic receptor tyrosine kinase (NTRK) fusion testing has both diagnostic and therapeutic implications for patient care. With 2 tumor-agnostic US Food and Drug Administration-approved tropomyosin receptor kinase (TRK) inhibitors, testing is increasingly used for therapeutic decision making. However, the testing landscape for NTRK fusions is complex, and optimal testing depends on the clinicopathologic scenario. OBJECTIVE.­: To compare different NTRK testing methods to help pathologists understand test features and performance characteristics and make appropriate selections for NTRK fusion detection for their laboratory and individual patient specimens. DATA SOURCES.­: A literature search for NTRK gene fusions and TRK protein was performed, including papers that discussed treatment, testing methodology, and detection or prevalence of fusion-positive cases. CONCLUSIONS.­: As standard of care in some tumor types, next-generation sequencing (NGS) panel testing is a cost effective and reliable way to detect a broad range of NTRK fusions. The design of the panel and use of DNA or RNA will affect performance characteristics. Pan-TRK immunohistochemistry may be used as a rapid, less expensive screen in cases that will not undergo routine NGS testing, or on specimens unsuitable for NGS testing. Fluorescence in situ hybridization may be appropriate for low-tumor-content specimens that are unsuitable for NGS testing. Quantitative reverse transcription polymerase chain reaction is best suited for monitoring low-level disease of a specific, previously identified target. This information should help laboratories develop a laboratory-specific NTRK testing algorithm that best suits their practice setting and patients' needs.

Laboratory and Clinical Implications of Incidental and Secondary Germline Findings During Tumor Testing.

CONTEXT.­: Next-generation sequencing is a powerful clinical tool for cancer management but can produce incidental/secondary findings that require special consideration. OBJECTIVE.­: To discuss clinical and laboratory issues related to incidental or secondary germline findings in the clinical setting of tumor testing and inform future guidelines in this area. DESIGN.­: A College of American Pathologists workgroup including representation from the American Society of Clinical Oncology, the Association for Molecular Pathology, and the American College of Medical Genetics and Genomics created a review of items that should be considered when developing guidelines for incidental or secondary findings when performing clinical tumor testing. RESULTS.­: Testing recommendations should be cognizant of the differences among anticipated incidental, unanticipated incidental, and secondary findings, and whether normal tissue is also tested. In addition to defining which variants will be reported, robust recommendations must also take into account test design and validation, reimbursement, cost, infrastructure, impact on reflex testing, and maintenance of proficiency. Care providers need to consider the potential of a test to uncover incidental or secondary findings, the recommendation of upfront counseling, the need for consent, the timing of testing and counseling, and that the exact significance of a finding may not be clear. CONCLUSIONS.­: As clinical oncology testing panels have become a mainstay of clinical cancer care, guidelines addressing the unique aspects of incidental and secondary findings in oncology testing are needed. This paper highlights clinical and laboratory considerations with regard to incidental/secondary findings and is a clarion call to create recommendations.

FET(EWSR1)-TFCP2 Rhabdomyosarcoma: An Additional Example of this Aggressive Variant with Predilection for the Gnathic Bones.

An example of a mandibular rhabdomyosarcoma in a 15-year-old male is described featuring EWSR1-TFCP2 fusion with homolateral lymph node metastasis and apparent metastasis to the thoracic vertebra T7. This type of rhabdomyosarcoma has preference for the craniofacial skeleton. Histologically, the tumor was composed of spindle and epithelioid cells characterized by nuclear pleomorphism, cytologic atypia and brisk mitotic activity. Immunohistochemically, it featured diffuse positive nuclear staining MYOD1, only focal staining for myogenin and patchy cytoplasmic staining for desmin. Tumor cells were positive for keratins and nuclear staining for SATB2 was also observed. Interestingly, tumor cells were diffusely positive for calponin. Currently, the patient is under chemotherapy treatment.

Langerhans cell histiocytosis with BRAF p.N486_P490del or MAP2K1 p.K57_G61del treated by the MEK inhibitor trametinib.

Activating variants of the MAPK pathway have been found in some Langerhans cell histiocytosis (LCH) lesions. Inhibition of the MAPK pathway with trametinib (MEK inhibitor) has been shown to induce responses in LCH patients. Two adolescent males with LCH driven by BRAF p.N486_P490del have received trametinib for >1 year with no reactivation in one and partial response in another (including stable lung disease). A third male with neonatal LCH and MAP2K1p.K57_G61del had a complete response to trametinib with no active disease after 22 months. All patients continue on trametinib monotherapy with tolerable skin and creatine phosphokinase toxicity.

Tracheal paraganglioma presenting as stridor in a pediatric patient, case report and literature review.

OBJECTIVE: To review tracheal paragangliomas and describe the clinical presentation, radiologic findings, operative management, and histologic findings of a pediatric patient who presented with stridor refractory to traditional asthma therapy. METHODS: Chart review of an 8-year-old male who presented to a tertiary care pediatric hospital and literature review of tracheal paragangliomas. RESULTS: We present the case of an 8-year-old male who presented with new-onset of wheezing and dyspnea on exertion. He was given a new diagnosis of asthma and treated with bronchodilators that failed to improve his symptoms, which progressed over 3 months until he presented urgently with biphasic stridor. Bedside flexible laryngoscopy failed to reveal an etiology. Computed tomography (CT) imaging demonstrated 17 × 12 × 16 mm exophytic mass arising from the posterior membranous trachea with extension of the mass to the border of the thyroid gland and separate from the esophagus. Magnetic resonance imaging (MRI) angiography confirmed vascular supply from the right thyrocervical trunk and inferior thyroid artery. Rigid microlaryngoscopy revealed a friable vascular polypoid mass 2 cm distal to the vocal folds with 75% obstruction of the airway from which a small biopsy was taken. Pathology confirmed paraganglioma with neuroendocrine cells arranged in "zellballen" architecture and strong immunopositivity for chromogranin and synaptophysin in the neuroendocrine cells and S100 immunopositivity in the sustentacular cells. The patient underwent complete open resection of the tumor including three tracheal rings with primary anastomosis. Final pathology confirmed paraganglioma and negative margins. Genetic screening revealed a succinate dehydrogenase complex subunit C (SDHC) germline mutation, confirming hereditary paraganglioma/pheochromocytoma syndrome. He remains well at 3 month follow up without dyspnea or stridor. CONCLUSION: Tracheal paragangliomas are exceptionally rare, with 12 reported cases. This is the only pediatric case reported. In pediatric patients with persistent airway complaints, subglottic and tracheal masses and obstruction should be considered. Due to the vascularity and endotracheal component of tracheal paragangliomas, a detailed surgical plan should consider embolization, endotracheal laser photocoagulation and electrocautery, and open surgical resection. Additionally, pediatric patients benefit from a multidisciplinary approach including radiology, endocrinology, and genetic counseling.