Novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and aggressive presentation.

Childhood melanoma is a rare and biologically heterogeneous pediatric malignancy. The differential diagnosis of pediatric melanoma is usually broad, including a wide variety of spindle cell or epithelioid neoplasms. Different molecular alterations affecting the MAPK and PI3K/AKT/mTOR pathways, tumor suppressor genes, and telomerase reactivation have been implicated in melanoma tumorigenesis and progression. Here, we report a novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and an aggressive clinical course.

Novel HNRNPM::LEUTX fusion resulting from chromothripsis of chromosome 19 in a pediatric undifferentiated small round cell neoplasm.

Small round cell neoplasms comprise a diverse group of tumors characterized by a primitive/undifferentiated appearance. Although several entities are associated with recurrent gene fusions, many of these neoplasms have not been fully characterized, and novel molecular alterations are being discovered. Here, we report an undifferentiated small round cell neoplasm arising in the anterior mediastinum of a 17-month-old female. The tumor harbored a novel HNRNPM::LEUTX fusion resulting from chromothripsis of chromosome 19, which was identified by whole transcriptome sequencing, but not by targeted sequencing. The structural variations caused by the chromothripsis event also challenged the interpretation of the targeted sequencing findings. This report expands the spectrum of gene partners involved in LEUTX fusions and underscores the value of whole transcriptome sequencing in the diagnostic workup of undifferentiated small round cell tumors. It also highlights the interpretive challenges associated with complex genomic alterations. A careful evidence-based analysis of sequencing data along with histopathologic correlation is essential to ensure correct categorization of fusions.

Giant focal nodular hyperplasia with a background of hepatic steatosis in a 14-year-old boy.

Giant focal nodular hyperplasia (GFNH) is rarely seen in children, presenting complex diagnostic and management considerations. Pathognomonic radiographic findings can be absent in this population, and the nuances of pathologic examination are critical. We present a child with a GFNH involving the right side of the liver arising in the background of hepatic steatosis. The details of the diagnosis and therapeutic decisions involved in his treatment are discussed.

Pulmonary Complications in Children Following Hematopoietic Cell Transplantation: A Case Report and Review of the Diagnostic Approach.

Pulmonary complications are common in children following hematopoietic cell transplantation (HCT) and contribute to their morbidity and mortality. Early diagnosis is essential for management and prevention of progression of lung injury and damage. In many cases, diagnosis can be challenging and may require diagnostic imaging and more invasive testing such as bronchoscopy and lung biopsy. We report the case of a 12-year-old girl who developed recurrent episodes of acute respiratory failure requiring intensive care unit admission in the post-HCT phase and describe the diagnostic and multidisciplinary approach for her management. In addition, we review the diagnostic approach of pulmonary complications post-HCT and highlight the utility and risks of bronchoscopy and lung biopsy in these children.

Adrenocortical Tumors in Children With Constitutive Chromosome 11p15 Paternal Uniparental Disomy: Implications for Diagnosis and Treatment.

Pediatric adrenocortical tumors (ACTs) are rare and heterogeneous. Approximately 50% of children with ACT carry a germline TP53 variant; however, the genetic underpinning of remaining cases has not been elucidated. In patients having germline TP53 variants, loss of maternal chromosome 11 and duplication of the paternal copy [paternal uniparental disomy, (UPD)] occurs early in tumorigenesis and explains the overexpression of IGF2, the hallmark of pediatric ACT. Beckwith-Wiedemann syndrome (BWS) is also associated with overexpression of IGF2 due to disruption of the 11p15 loci, including segmental UPD. Here, we report six children with ACT with wild type TP53 and germline paternal 11p15 UPD. Median age of five girls and one boy was 3.2 years (range 0.5-11 years). Two patients met the criteria for BWS before diagnosis of ACT. However, ACT was the first and only manifestation of paternal 11p15 UPD in four children. Tumor weight ranged from 21.5 g to 550 g. Despite poor prognostic features at presentation, such as pulmonary metastasis, bilateral adrenal involvement, and large tumors, all patients are alive 8-21 years after cancer diagnosis. Our observations suggest that children with ACT and wild type TP53, irrespective of their age, should be screened for germline abnormalities in chromosome 11p15.

Do nontriploid partial hydatidiform moles exist? A histologic and flow cytometric reevaluation of nontriploid specimens.

OBJECTIVE: To study whether nontriploid partial hydatidiform moles truly exist. STUDY DESIGN: We conducted a reevaluation of pathology and ploidy in 19 putative nontriploid partial hydatidiform moles using standardized histologic diagnostic criteria and repeat flow cytometric testing by the Hedley technique. RESULTS: On review of the 19 moles, 53% (10/19) were diploid nonpartial moles (initially pathologically misclassified), and 37% (7/19) were triploid partial moles (initial ploidy misclassifications). One additional case (5%) was a diploid early complete mole (initially pathologically misclassified). CONCLUSION: Nontriploid partial moles probably do not exist: careful reevaluation of putative specimens will probably uncover pathologic or ploid errors in almost all cases.

Malignant triton tumor in a patient with Li-Fraumeni syndrome and a novel TP53 mutation.

We report a 3-year-old boy with a malignant triton tumor (MTT) involving the left masticator space with local invasion and regional lymph node metastasis. Family history and detection of a novel germline TP53 mutation confirmed his diagnosis of Li Fraumeni syndrome (LFS). MTT has not been previously described in association with LFS. This case along with a comprehensive review of the literature, illustrate the importance of both somatic and germline TP53 mutations in the pathogenesis MTT. The tumor could not be resected and he was successfully treated with intensive induction chemotherapy, irradiation, and high-dose chemotherapy with autologous stem cell transplantation.

Squamous cell carcinoma arising in a pediatric intra- and paravertebral teratoma.

A 7-year-old boy presented with a 1-year history of back pain radiating to his left scapula and arm, with tenderness to palpation over the area. Laboratory studies were unremarkable. Computed tomographic scan showed a mixed lytic and sclerotic process at the T5-T6 level of the vertebral column in continuity with an adjacent paravertebral soft tissue mass. Nuclear medicine scan demonstrated increased uptake in the T5 vertebral body. Histology revealed invasive squamous cell carcinoma infiltrating mature, gliotic neural tissue, with areas of necrosis and prominent perivascular space involvement. Associated vertebral fragments showed bone destruction, reactive bone formation, and fibrosis. By immunohistochemistry, the carcinoma cells were positive for cytokeratin AE1/AE3, cytokeratin 5/6, EMA, and MIC-2 (membranous staining). The mature neural tissue was positive for GFAP; immature neural elements were not identified. Based on morphologic, immunohistochemical, and clinical features, this lesion was diagnosed as invasive squamous cell carcinoma arising within an intravertebral and paravertebral teratoma.

Identification of SYT-SSX transcripts from synovial sarcomas using RT-multiplex PCR and capillary electrophoresis.

Synovial sarcomas are highly malignant tumors of soft tissue which are characterized by the t(X;18) resulting in SYT-SSX fusion transcript production. Diagnosis of these tumors based on histology can be challenging, particularly when minimal biopsy specimens are presented to the pathologist. Demonstration by molecular methods of SYT-SSX transcripts is a useful adjunct for diagnosis in these situations. We have developed an assay, which combines one-step RT-multiplex PCR with capillary electrophoresis to detect and genotype the SYT-SSX transcripts from synovial sarcomas. Small amplicons from chimeric transcripts as well as GAPD transcripts are differentially labeled with fluorophores, allowing detection and size discrimination by capillary electrophoresis. In a study of 32 formalin-fixed soft tissue tumor specimens, the assay detected chimeric transcripts from 17/22 (77%) synovial sarcomas. All five assay negative specimens yielded no intact RNA as evidenced by lack of a GAPD amplicon. Chimeric transcripts were not detected in 9/9 malignant peripheral nerve sheath tumors or 1/1 epithelioid sarcoma. Representative amplicons were sequenced and confirmed the genotype results obtained by capillary electrophoresis. One-step RT-multiplex PCR combined with capillary electrophoresis is a rapid and accurate method for the detection and genotypic classification of SYT-SSX transcripts from fixed tissue specimens.

Myofibromatosis: imaging characteristics.

BACKGROUND: Infantile myofibromatosis is the most common fibrous tumor of infancy. It can involve the skin, muscle, bone, and viscera. This uncommon entity is subdivided into solitary and multicentric forms, with or without visceral involvement. OBJECTIVE: To describe the imaging characteristics of extracranial myofibromatosis. MATERIALS AND METHODS: Six infants, aged 1 day-1 week, were evaluated by imaging. All six patients had evaluation of one of the masses by US; four patients had CT evaluation of at least one of the masses; and five patients had evaluation by MRI. RESULTS: The US appearance of the myofibromas included a mass with a purely anechoic center with a thick wall, a mass with a partially anechoic center, and a mass without anechoic components. On enhanced CT, the masses had lower or similar attenuation compared to adjacent muscle, with some masses exhibiting peripheral enhancement. The MR appearance consisted of low signal on T1-weighted imaging. On T2-weighted imaging, two had low signal of the center and the other three had high signal. All masses showed peripheral enhancement after gadolinium administration. CONCLUSIONS: Myofibromas have variable appearance on US, with a mass with an anechoic center being the most common feature. On CT, the mass can exhibit peripheral enhancement, calcifications, and erosion of adjacent bone. The MR appearance consisted of low signal on T1-weighted imaging and high or low signal of the center on T2-weighted imaging. All masses showed peripheral enhancement after gadolinium administration.

Aggressive hepatic angiomyolipoma in a child.

Angiomyolipoma is a tumor of the kidney and, more rarely, the liver, which histologically consists of smooth muscle cells, adipose cells, and abnormal blood vessels in varying proportions. This tumor is generally benign and resection is curative, but here the authors present the case of a 14-year-old girl with an unusual primary hepatic angiomyolipoma that recurred following resection and behaved aggressively. Despite stabilization with a number of novel therapies, the child ultimately died of progressive disease.

Metastatic neuroblastoma presenting with binocular blindness from intracranial compression of the optic nerves.

A 2-year-old boy with blindness as an isolated symptom was found to have no light perception binocularly because of compression of both optic nerves by a neuroblastoma infiltrating the walls of the optic canals and medial sphenoid bone. Imaging disclosed a primary tumor near the kidney and multiple osseous metastases. Although neuroblastoma commonly causes blindness by metastasis to the orbit, it rarely causes bilateral blindness from intracranial compression of the optic nerves. This is the first report of bilateral blindness as the presenting feature.