Diagnostic utility of molecular and cytogenetic analysis in lipoblastoma: a study of two cases and review of the literature

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.

Lipoblastoma: computed tomographic and magnetic resonance imaging features correlate with tumor behavior and pathology

BACKGROUND

Lipoblastoma is a rare benign neoplasm of immature fat cells in children. Imaging appearances are frequently complex, sometimes simulating liposarcoma.

OBJECTIVE

To characterize features of lipoblastoma on MRI and CT in comparison with recurrence risk.

MATERIALS AND METHODS

We identified cases via retrospective review of histopathology-proven lipoblastoma cases in a large referral database and a pediatric medical center. Two radiologists scored CT and MRI on the basis of lesion features.

RESULTS

We included a total of 56 children (32 boys and 24 girls) with a mean age of 2.6 years (range 0.1-13 years). Extremity lesions were most common (27%), followed by neck (19%), gluteal region (18%), chest (14%) and mesentery (14%). Children most commonly presented with painless masses (73%), followed by dyspnea (9%), distension (9%) and pain (7%). Non-adipose soft-tissue components were identified on CT and MRI in 78% of cases. Significant (moderate or marked) septations were noted in 59% and enhancement in 35%. Compartmental invasion was present in 43% of cases. Of paraspinal cases, 38% involved the neural foramina or central canal. Lesion complexity did not significantly correlate with age. Recurrence was observed in 9% of cases and was significantly correlated with compartmental invasion (correlation: 0.303, P=0.009) and septation complexity (correlation: 0.227, P=0.038) on initial imaging.

CONCLUSION

Although lipoblastoma is a fat-containing entity, many lesions demonstrate marked complexity and local infiltration that resemble liposarcoma, which is exceedingly rare in younger children. Compartmental invasion and thicker septations appear to confer greater risk of recurrence following resection.

New molecular insights into the pathogenesis of lipoblastomas: clinicopathologic, immunohistochemical, and molecular analysis in pediatric cases

Lipoblastomas can occasionally require further molecular confirmation when occurring outside of the usual age groups or demonstrating unusual morphology. We reviewed 28 lipoblastomas with 16 controls. Lipoblastomas were subdivided into myxoid (n = 7), classic (n = 9), or lipoma-like (n = 12) subtypes. PLAG1 immunohistochemistry, PLAG1 fluorescence in situ hybridization (FISH), and targeted RNA sequencing were performed on formalin-fixed paraffin-embedded tissue. Karyotypes were available in a subset of lipoblastomas (n = 9). Gene rearrangements were identified in 17/25 (68%) lipoblastomas, including PLAG1 (15/25, 60%) and HMGA2 (2/25, 8%). Five novel fusion partners (DDX6, KLF10, and KANSL1L with PLAG1 and EP400 and FGD6 with HMGA2) were found. PLAG1 immunohistochemistry was positive (nuclear, moderate/strong) in myxoid and classic subtypes lipoblastomas with preferential expression in mesenchymal cells within myxoid stroma and fibrous septa and negative in all controls. When comparing PLAG1 immunohistochemistry with molecular testing (FISH and/or RNA sequencing and/or karyotype), concordant results were noted in 13/25 (52%) cases, increasing to 15/25 (60%) after slight adjustment of the PLAG1 FISH positive threshold. In myxoid and classic lipoblastomas, PLAG1 immunohistochemistry seems to be a better surrogate marker for PLAG1 rearrangement, as compared with lipoma-like subtypes. In lipoma-like subtypes, targeted RNA sequencing appears to detect PLAG1 fusions better than FISH and immunohistochemistry. The preferential expression of PLAG1 in the mesenchymal and fibroblast-like cells deserves further investigation as the putative cell of origin in lipoblastoma.

Rapidly Growing Facial Tumor in a 5-Year-Old Girl

The aim of this study is to describe the clinical, radiological and histological characteristics that define lipoblastomas with special emphasis on differential diagnosis. The patient is a 5-year-old girl who consulted for a rapidly growing lower cheek tumor. This study analyzes, evaluates, and discusses the issues that need to be addressed throughout the process that affect treatment planning and provides an updated review of these rare head-and-neck tumors.

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.

A contemporary review of myxoid adipocytic tumors

Myxoid adipocytic tumors encompass a broad heterogeneous group of benign and malignant adipocytic tumors, which are typically myxoid (e.g. myxoid liposarcoma, lipoblastoma and lipoblastoma-like tumor of the vulva) or may occasionally appear predominantly myxoid (e.g. pleomorphic liposarcoma, atypical lipomatous tumor, dedifferentiated liposarcoma, chondroid lipoma, spindle cell/pleomorphic lipoma, atypical spindle cell lipomatous tumor and atypical pleomorphic lipomatous tumor). There have been significant advances in recent years in classification and understanding the pathogenesis of adipocytic tumors, based on the correlation of histologic, immunohistochemical, and cytogenetic/molecular findings. Despite these advances, the morphologic diagnosis and accurate classification of a myxoid adipocytic tumor can be challenging due to major morphologic overlap between myxoid adipocytic and non-adipocytic tumors. This article will provide a review on the currently known morphological, immunohistochemical and molecular features of myxoid adipocytic tumors and their differential diagnosis.

Mesenchymal Neoplasms of the Genitourinary System: A Selected Review with Recent Advances in Clinical, Diagnostic, and Molecular Findings

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features.

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.

Spinal dumbbell lipoblastoma: a case-based update

INTRODUCTION

Lipoblastomas are benign tumors that arise from the proliferation of fetal adipose tissue. They are frequently found in the extremities, in the head, and in the neck. Dumbbell conformation (which refers to epidural tumors with extraspinal extension) has been described in only seven lipoblastoma cases so far.

CASE REPORT

We describe an 11-month-old patient with a large mediastinal dumbbell lipoblastoma. The mass was excised, but it recurred 1 year later when the MRI showed also multiple pleural lipoblastomatous lesions, thus establishing the diagnosis of lipoblastomatosis. The tumor has been removed with a second surgical procedure.

CONCLUSION

Radical excision of lipoblastomas is the gold standard but is not always possible to achieve. Residual lesions can be managed conservatively, on the basis of the benign nature of the tumor and of its potential maturation to normal fat. Recurrence of lipoblastoma appears in 15 % of non-radical excisions but has not yet been described in the form of lipoblastomatosis. A second surgery is indicated if the tumor mass reaches large dimensions, if it increases in size, and if it threatens the functionality of vital organs such as the spinal cord.

Undifferentiated myxoid lipoblastoma with PLAG1-HAS2 fusion in an infant; morphologically mimicking primitive myxoid mesenchymal tumor of infancy (PMMTI)--diagnostic importance of cytogenetic and molecular testing and literature review

Lipoblastoma is a benign myxoid neoplasm arising in young children that typically demonstrates adipose differentiation. It is often morphologically indistinguishable from primitive myxoid mesenchymal tumor of infancy (PMMTI), which is characterized by a well-circumscribed myxoid mass with a proliferation of primitive mesenchymal cells with mild cytologic atypia. PMMTI occurs in the first year of life and is known to have locally aggressive behavior. No specific genetic rearrangements have been reported to date. In contrast, the presence of PLAG1 (Pleomorphic Adenoma Gene 1) rearrangement is diagnostic for lipoblastoma. We hereby demonstrate the combined application of multiple approaches to tackle the diagnostic challenges of a rapidly growing neck tumor in a 3-month-old female. An incisional tumor biopsy had features of an undifferentiated, myxoid mesenchymal neoplasm mimicking PMMTI. However, tumor cells showed diffuse nuclear expression by immunohistochemical (IHC) stain. Conventional cytogenetic and fluorescence in situ hybridization (FISH) analyses as well as next generation sequencing (NGS) demonstrated evidence of PLAG1 rearrangement, confirming the diagnosis of lipoblastoma. This experience warrants that undifferentiated myxoid lipoblastoma can mimic PMMTI, and the combination of cytogenetic and molecular approaches is essential to distinguish these two myxoid neoplasms. Literature on lipoblastomas with relevant molecular and cytogenetic findings is summarized. Our case is the first lipoblastoma diagnosed with a PLAG1 fusion defined by NGS technology.

A case of unusual histology of infantile lipoblastoma confirmed by PLAG1 rearrangement

Lipoblastoma, a relatively rare benign adipose neoplasm, predominantly affects children younger than 3 years of age. We herein report the case of a 7-month-old girl with an unusual myxomatous histology of lipoblastoma. A rapidly growing mass was detected in the subcutaneous area of the left buttock. Histologically, the tumor consisted of abundant myxoid stroma exhibiting cellular atypia and a high mitotic activity. Although the histological findings were unusual, the tumor was diagnosed as a lipoblastoma according to both PLAG1 immunohistochemistry and the presence of PLAG1 rearrangement on fluorescence in situ hybridization.