Chromothripsis in lipoblastoma: second reported case with complex PLAG1 rearrangement

Lipoblastomas (LPBs) are rare benign neoplasms derived from embryonal adipose that occur predominantly in childhood. LPBs typically present with numeric or structural rearrangements of chromosome 8, the majority of which involve the pleomorphic adenoma gene 1 (PLAG1) proto-oncogene on chromosome 8q12. Here, we report on a LPB case on which showed evidence of chromothripsis. This is the second reported case of chromothripsis in LPB.

Three Novel Aberrations Involving PLAG1 Leading to Lipoblastoma in Three Different Patients: High Amplification, Partial Deletion, and a Unique Complex Rearrangement

Lipoblastoma is a rare benign neoplasm with overlapping histology with other lipomatous tumors. Genetic aberrations including translocations of 8q and splitting of the PLAG1 probe leading to "promoter swapping" and gains of chromosome 8 or PLAG1 foci have been described in lipoblastoma. Here, we report 3 lipoblastomas revealing novel genetic aberrations involving PLAG1: a high level of PLAG1 amplification up to 50 copies in a 4-year-old girl with recurrence of a right flank mass, a partial deletion of PLAG1 with the flanking junction breakpoints involving the 3'PLAG1 and 5'HAS2 genes in a 17-month-old boy with a retroperitoneal mass, and an insertion of 2q31 into 8q11.2 and translocation of 8q to 2q with the latter translocated onto 12q leading to separation of the PLAG1 FISH probe in a 5-year-old girl with a left back mass. Our novel cytogenetic findings further expand the mechanisms of PLAG1 transcriptional upregulation in lipoblastoma pathogenesis.

Plag1 and Plagl2 have overlapping and distinct functions in telencephalic development

The Plag gene family has three members; Plagl1/Zac1, which is a tumor suppressor gene, and Plag1 and Plagl2, which are proto-oncogenes. All three genes are known to be expressed in embryonic neural progenitors, and Zac1 regulates proliferation, neuronal differentiation and migration in the developing neocortex. Here we examined the functions of Plag1 and Plagl2 in neocortical development. We first attempted, and were unable to generate, E12.5 Plag1;Plagl2 double mutants, indicating that at least one Plag1 or Plagl2 gene copy is required for embryonic survival. We therefore focused on single mutants, revealing a telencephalic patterning defect in E12.5 Plagl2 mutants and a proliferation/differentiation defect in Plag1 mutant neocortices. Specifically, the ventral pallium, a dorsal telencephalic territory, expands into the ventral telencephalon in Plagl2 mutants. In contrast, Plag1 mutants develop normal regional territories, but neocortical progenitors proliferate less and instead produce more neurons. Finally, in gain-of-function studies, both Plag1 and Plagl2 reduce neurogenesis and increase BrdU-uptake, indicative of enhanced proliferation, but while Plagl2 effects on proliferation are more immediate, Plag1 effects are delayed. Taken together, we found that the Plag proto-oncogenes genes are essential regulators of neocortical development and although Plag1 and Plagl2 functions are similar, they do not entirely overlap. This article has an associated First Person interview with the first author of the paper.

Lipoblastoma: a clinicopathologic review of 23 cases from a major tertiary care center plus detailed review of literature

Objective

Lipoblastoma is a rare neoplasm that occurs mostly in infants and children. Although benign, it has a tendency for local recurrence.

Results

Clinical and pathological features of 23 cases of lipoblastoma described. Patients’ age ranged from 8 months to 18 years with mean and median age 4.1 and 2.5 years, respectively. Male:female ratio was 2.8:1. Most common sites were lower extremities (9 cases), followed by abdominal cavity and retroperitoneum (4 cases), and scrotum/groin (3 cases). Grossly, 22 tumors were well circumscribed and multi nodular. All cases showed lobules composed of adipocytes and lipoblasts with intervening fibrous septa and fine vascular network. Myxoid change, capsule formation and septation were seen in all cases. Zonation was seen in 2 cases. Follow-up was available in 14 out of 23 patients. Of these, 13 were alive and free of disease with no evidence of any recurrent lesion. One patient with a mediastinal infiltrating lipoblastoma experienced 4 recurrences. Lipoblastoma is a benign adipocytic neoplasm of infants and young children. Correlation of clinical and histological features helps in reaching a correct diagnosis. Owing to a high recurrence rate following incomplete resection, a complete resection is essential. Prognosis is excellent after complete resection.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3153-8) contains supplementary material, which is available to authorized users.

Pediatric dermatohistopathology--histopathology of skin diseases in newborns and infants

While neonatal skin physiology has been thoroughly examined using non-invasive techniques in recent years, only few systematic studies and review articles addressing the histopathology of neonatal skin have been published thus far. In most cases, histopathological findings of dermatoses in neonatal skin do not significantly differ from those seen in adult skin. Nevertheless, a comprehensive knowledge of embryonic and fetal skin development as well as the microanatomical structure of neonatal skin can contribute to a better understanding of various dermatoses of infancy. In the first part of this review article, we present the histopathological features of such skin diseases, which, though generally rare, almost exclusively appear during the first weeks of life due to distinctive structural and functional features of neonatal skin. The second part is dedicated to classic dermatoses of infancy and their histopathological features.

Correlated expression of HMGA2 and PLAG1 in thyroid tumors, uterine leiomyomas and experimental models

In pleomorphic adenomas of the salivary glands (PASG) recurrent chromosomal rearrangements affecting either 8q12 or 12q14∼15 lead to an overexpression of the genes of the genuine transcription factor PLAG1 or the architectural transcription factor HMGA2, respectively. Both genes are also affected by recurrent chromosomal rearrangements in benign adipocytic tumors as e. g. lipomas and lipoblastomas. Herein, we observed a strong correlation between the expression of HMGA2 and PLAG1 in 14 benign and 23 malignant thyroid tumors. To address the question if PLAG1 can be activated by HMGA2, the expression of both genes was quantified in 32 uterine leiomyomas 17 of which exhibited an overexpression of HMGA2. All leiomyomas with HMGA2 overexpression also revealed an activation of PLAG1 in the absence of detectable chromosome 8 abnormalities affecting the PLAG1 locus. To further investigate if the overexpression of PLAG1 is inducible by HMGA2 alone, HMGA2 was transiently overexpressed in MCF-7 cells. An increased PLAG1 expression was observed 24 and 48 h after transfection. Likewise, stimulation of HMGA2 by FGF1 in adipose tissue-derived stem cells led to a simultaneous increase of PLAG1 mRNA. Altogether, these data suggest that HMGA2 is an upstream activator of PLAG1. Accordingly, this may explain the formation of tumors as similar as lipomas and lipoblastomas resulting from an activation of either of both genes by chromosomal rearrangements.

A novel t(3;8)(p13;q21.1) translocation in a case of lipoblastoma

Lipoblastoma is a rare benign neoplasm of embryonic white fatty tissue primarily found in the extremities of children <3 years old (Batanian et al., Cancer Genet Cytogenet 125(1):10-13, 2001; McVay MR et al., J Pediatr Surg 41(6):1067-1071, 2006; Kamal et al., J Pediatr Surg 46(7):E9-E12, 2011). Translocations affecting the 8q11-13 region are commonly reported with lipoblastoma and proper diagnosis requires cytogenetic analysis to distinguish it from malignant myxoid liposarcoma (Miller et al., J Pediatr Surg 32(12):1771-1772, 1997; Morerio et al., Pediatr Blood Cancer 52(1):132-134, 2009). We describe an additional case of lipoblastoma containing a new translocation t(3;8)(p13;q21.1), which has not previously been reported in a healthy asymptomatic child.

Adipose and myxoid tumors of childhood and adolescence

Adipose and myxoid tumors in children are an unusual and challenging group of neoplasms that have some unique aspects in contrast to these tumors in adults. Less than 10% of soft tissue neoplasms in the 1st 2 decades of life have an adipose phenotype and most are benign. The most common are various types of lipoma and lipoblastoma. Liposarcoma in young patients is rare and has a distinctive distribution of histologic subtypes, including classic myxoid liposarcoma, and unusual variants, such as pleomorphic-myxoid liposarcoma. Pathologic examination enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic studies, is useful for classification of difficult cases. Myxoid tumors can overlap with adipose tumors and are included in this review because of the morphologic similarities and importance of diagnostic accuracy. This article reviews the clinicopathologic features of adipose and myxoid tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents and the differential diagnosis.

Contributions of cytogenetics and molecular cytogenetics to the diagnosis of adipocytic tumors

Over the last 20 years, a number of tumor-specific chromosomal translocations and associated fusion genes have been identified for mesenchymal neoplasms including adipocytic tumors. The addition of molecular cytogenetic techniques, especially fluorescence in situ hybridization (FISH), has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal translocations and/or other rearrangements in adipocytic tumors. Indeed, most resent molecular cytogenetic analysis has demonstrated a translocation t(11;16)(q13;p13) that produces a C11orf95-MKL2 fusion gene in chondroid lipoma. Additionally, it is well recognized that supernumerary ring and/or giant rod chromosomes are characteristic for atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma, and amplification of 12q13–15 involving the MDM2, CDK4, and CPM genes is shown by FISH in these tumors. Moreover, myxoid/round cell liposarcoma is characterized by a translocation t(12;16)(q13;p11) that fuses the DDIT3 and FUS genes. This paper provides an overview of the role of conventional cytogenetics and molecular cytogenetics in the diagnosis of adipocytic tumors.

Mediastinal lipoblastomatosis: report of a case with complex karyotype and review of the literature

Lipoblastoma or lipoblastomatosis is an uncommon fatty tumor seen in children up to the age of 5 years, with very rare exceptions above that age. It usually occurs in the extremities, but it can arise in other anatomical sites, including the head and neck area, trunk, mediastinum, mesentry, and retroperitoneum. We report a 9-month-old boy with mediastinal lipoblastomatosis showing unusually complex chromosomal aberrations. Five years following surgical excision that was incomplete as a result of the tumor's proximity to major blood vessels, the patient developed a recurrence of the tumor in the mediastinum with extension to the neck and spinal dura. We present a review of the literature related to mediastinal lipoblastoma and lipoblastomatosis and the chromosomal abnormalities of these tumors.