Lipoblastoma-Like Tumor and Fibrosarcoma-Like Lipomatous Neoplasm Represent the Same Entity: A Clinicopathologic and Molecular Genetic Study of 23 Cases Occurring in Both Men and Women at Diverse Locations.

Lipoblastoma-like tumor (LLT) is a benign soft tissue tumor demonstrating mixed morphologic features of lipoblastoma, myxoid liposarcoma, and spindle cell lipoma but lacking genetic alterations associated with those tumors. LLT was originally thought to be specific to the vulva but has since been reported in the paratesticular region. The morphologic features of LLT overlap with those of "fibrosarcoma-like lipomatous neoplasm" (FLLN), a rare, indolent adipocytic neoplasm considered by some to form part of the spectrum of atypical spindle cell and pleomorphic lipomatous tumor. We compared the morphologic, immunohistochemical, and genetic features of 23 tumors previously classified as LLT (n = 17) and FLLN (n = 6). The 23 tumors occurred in 13 women and 10 men (mean age, 42 years; range, 17 to 80 years). Eighteen (78%) cases arose in the inguinogenital region, whereas 5 tumors (22%) involved noninguinogenital soft tissue, including the flank (n = 1), shoulder (n = 1), foot (n = 1), forearm (n = 1), and chest wall (n = 1). Microscopically, the tumors were lobulated and septated, with variably collagenized fibromyxoid stroma, prominent thin-walled vessels, scattered univacuolated or bivacuolated lipoblasts, and a minor component of mature adipose tissue. Using immunohistochemistry, 5 tumors (42%) showed complete RB1 loss, with partial loss in 7 cases (58%). RNA sequencing, chromosomal microarray, and DNA next-generation sequencing study results were negative for significant alterations. There were no clinical, morphologic, immunohistochemical, or molecular genetic differences between cases previously classified as LLT or FLLN. Clinical follow-up (11 patients [48%]; range, 2-276 months; mean, 48.2 months) showed all patients were alive without disease, and only one patient had experienced a single local recurrence. We conclude that LLT and FLLN represent the same entity, for which "LLT" seems most appropriate. LLT may occur in either sex and any superficial soft tissue location. Careful morphologic study and appropriate ancillary testing should allow for the distinction of LLT from its potential mimics.

Lipoblastomatosis Extended into the Lumbar Spinal Canal in a Child: A Case Report.

INTRODUCTION: Lipoblastoma and lipoblastomatosis are rare benign mesenchymal adipose tumors that originate from embryonic white adipocytes and occur most commonly in infancy and early childhood. Lipoblastomas occur in the extremities and trunk, including the retroperitoneum and peritoneal cavity. Therefore, infiltration into the spinal canal has rarely been reported. CASE PRESENTATION: A 4-year-old girl presented to our clinic because of difficulty sitting on the floor with her legs straight. She also complained of enuresis and constipation for the past 6 months with persistent headaches and back pain evoked by body anteflexion. A magnetic resonance imaging revealed a massive lesion of the psoas major muscle, retroperitoneal, and subcutaneous spaces, extending into the spinal epidural space between L2 and S1. The patient underwent surgery which resulted in gross total removal of the tumor from the spinal canal. The mass was yellowish, soft, lobulated, fatty, and easily removed from the surrounding structures. Pathology confirmed the diagnosis of lipoblastoma. The postoperative course was uneventful, and the patient was discharged without any signs of neurological deficit. CONCLUSION: We herein discuss a rare case of lipoblastoma extending into the spinal canal, resulting in neurological symptoms. Although this tumor is benign with no potential for metastasis, it is prone to local recurrence. Therefore, close postoperative observation should be performed.

PLAG1 Immunohistochemical Staining Is a Surrogate Marker for PLAG1 Fusions in Lipoblastomas.

BACKGROUND: The hallmark of lipoblastoma is a PLAG1 fusion. PLAG1 protein overexpression has been reported in sporadic PLAG1-rearranged lipoblastomas. METHODS: We evaluated the utility of PLAG1 immunohistochemical staining (IHC) in 34 pediatric lipomatous tumors, correlating the results with histology and conventional cytogenetics, FISH and/or next generation sequencing (NGS) results. RESULTS: The study included 24 lipoblastomas, divided into 2 groups designated as "Lipoblastoma 1" with both lipoblastoma histology and PLAG1 rearrangement (n = 16) and "Lipoblastoma 2" with lipoblastoma histology but without PLAG1 cytogenetic rearrangement (n = 8), and 10 lipomas with neither lipoblastoma histology nor a PLAG1 rearrangement. Using the presence of a fusion as the "gold standard" for diagnosing lipoblastoma (Lipoblastoma 1), the sensitivity of PLAG1 IHC was 94%. Using histologic features alone (Lipoblastoma 1 + 2), the sensitivity was 96%. Specificity, as defined by the ability to distinguish lipoma from lipoblastoma, was 100%, as there were no false positives in the lipoma group. CONCLUSIONS: Cytogenetics/molecular testing is expensive and may not be ideal for detecting PLAG1 fusions because PLAG1 fusions are often cytogenetically cryptic and NGS panels may not include all partner genes. PLAG1 IHC is an inexpensive surrogate marker of PLAG1 fusions and may be useful in distinguishing lipoblastomas from lipomas.

Pediatric fibromyxoid tumor with PLAG1 fusion: An emerging entity with a novel intracranial location.

Translocations involving PLAG1 occur in several tumors, most commonly pleomorphic adenoma and lipoblastoma. Recently, a distinctive soft tissue tumor with a PLAG1 fusion has been reported in the pediatric age group. These are low grade tumors with a fibroblastic or mixed fibroblastic and myxoid morphology but no other lines of differentiation. They are typically immunopositive for desmin and CD34. The partner genes for these tumors have included YWHAZ, EEF1A1, ZFHX4l, CHCHD7, and PCMTD1. We report another case of this fibromyxoid tumor with a PLAG1 fusion, this time with COL3A1 as the partner gene. The fusion placed expression of a full-length PLAG1 protein under the control of the constitutively active COL3A1 promoter. Overexpression of PLAG1 was confirmed by diffusely positive immunostaining for PLAG1. The most novel aspect of this tumor is the intracranial location. Opinion has been divided over whether these tumors are a specific entity, or related to lipoblastoma, since that tumor also typically occurs in soft tissue in the pediatric age group and shows many of the same gene fusions. However, lipoblastoma has never been reported in an intracranial location and, thus, our case provides compelling evidence that this fibromyxoid tumor is indeed a distinct entity.

Lipoblastoma of scalp in a 4-month-old patient: an extremely rare case report and review of the literature.

Lipoblastoma is a rare benign tumor originating from adipose tissue, usually seen in infancy and early childhood. Here, we present a case of scalp lipoblastoma in a 4-month-old that we treated surgically and review the literature. Although lipoblastomas may be seen in various locations during infancy and early childhood, rarely, they can also develop in the scalp.

Diagnosis and treatment of benign adipocytic tumors in children.

PURPOSE: To describe demographic, clinical, diagnostic and therapeutic aspects of pediatric patients with benign adipocytic tumors admitted to a high complexity teaching hospital from 2007 to 2021. METHODS: Retrospective observational descriptive study. Patient information was retrieved from clinical records. A descriptive analysis was carried out for qualitative data and frequencies were calculated for quantitative data. RESULTS: 76 patients were included with a mean age of 7.5 years old where 60.5% were boys. The main symptom was a mass (73.7%) mostly found in the lower limbs (23.6%). Congenital birth defects were identified in 48.6% of the cases. Preoperative imaging was available in 78.9% of the patients allowing characterization of lesions or differential diagnosis. The therapeutic goal was resection with negative margins, which was feasible in all cases except for one case. The histopathological diagnosis was lipoma in 68.4% of the cases followed by lipoblastoma in 13.1%. The mean follow-up period was 17.9 months. 79.7% of the patients were asymptomatic at their last out-patient visit. CONCLUSION: Benign adipocytic tumors constitute a wide spectrum of lesions, which involve diverse anatomic segments from the neural axis to the inguinoscrotal region. The present work contributes to the general understanding of the clinical presentation and differential diagnosis for these infrequent neoplasms.

Lipoblastomas presenting in older children and adults: analysis of 22 cases with identification of novel PLAG1 fusion partners.

Lipoblastomas are benign neoplasms of embryonal white fat that typically present in the first 3 years of life and show a lobular arrangement of maturing adipocytes with variable degrees of myxoid change. We systematically studied the clinicopathologic and genetic features of lipoblastomas arising in older children and adults. Cases with a diagnosis of lipoblastoma or maturing lipoblastoma in patients >3 years of age were retrieved from our archives. Immunostaining for CD34 and desmin and molecular studies (FISH, RNA sequencing) were performed. Twenty-two cases (8F; 14M) were identified in patients ranging from 4 to 44 years of age (median 10 years). Sites included extremity (n = 15), head and neck (n = 4), and trunk (n = 3) with tumor sizes varying from 1.6 to 17.5 cm (median 5). Only three tumors had histologic features of "conventional" lipoblastoma. The majority of tumors (n = 14) were composed of variably sized lobules of mature adipose tissue partitioned by thin fibrous septa ("maturing"). The remaining five cases consisted predominantly of bland spindled to plump ovoid cells embedded in a fibrous stroma, with a vaguely plexiform arrangement of small myxoid and adipocytic nodules ("fibroblastic"). CD34 was diffusely positive in all cases tested (21/21), while desmin immunoreactivity was identified in 12 of 21 cases (diffuse = 7, focal = 5). PLAG1 rearrangements were identified in 13 tumors in the entire cohort (59%), including all 5 fibroblastic tumors. RNA sequencing detected eight PLAG1 fusion partners, of which two were known (CHCHD7 and COL3A1) and six were novel (SRSF3, HNRNPC, PCMTD1, YWHAZ, CTDSP2, and PPP2R2A). Twelve cases had follow-up (1-107 months; median 21 months), and no recurrences were reported. Lipoblastomas may occur in older children and adults and may be difficult to recognize due to their predominantly adipocytic or fibrous appearance. Awareness that lipoblastomas may occur in older patients, careful evaluation for foci showing more typical morphologic features, ancillary immunohistochemistry for CD34 and desmin, and molecular genetic studies to identify PLAG1 rearrangements are the keys to recognizing these tumors.

A large retroperitoneal lipoblastoma as an incidental finding: a case report.

BACKGROUND: Lipoblastoma is a rare benign mesenchymal neoplasm of infancy that most commonly occurs on the extremities and trunk but can arise at variable sites of the body. Retroperitoneal lipoblastomas are particularly rare but can grow to enormous size, and preoperative diagnosis is difficult with diverse, mostly malignant differential diagnoses that would lead to aggressive therapy. Since lipoblastoma is a benign tumor that has an excellent prognosis after resection, correct diagnosis is crucial. CASE PRESENTATION: A case of a large retroperitoneal tumor of a 24-month old infant that was clinically suspicious of a malignant tumor is presented. Due to proximity to the right kidney, clinically most probably a nephroblastoma or clear cell sarcoma of the kidney was suspected. Radiological findings were ambiguous. Therefore, the mass was biopsied, and histology revealed an adipocytic lesion. Although mostly composed of mature adipocytes, in view of the age of the patient, the differential diagnosis of a (maturing) lipoblastoma was raised, which was supported by molecular analysis demonstrating a HAS2-PLAG1 fusion. The tumor was completely resected, and further histopathological workup led to the final diagnosis of a 13 cm large retroperitoneal maturing lipoblastoma. The child recovered promptly from surgery and showed no evidence of recurrence so far. CONCLUSION: Although rare, lipoblastoma should be included in the differential diagnoses of retroperitoneal tumors in infants and children, and molecular diagnostic approaches could be a helpful diagnostic adjunct in challenging cases.

Lipoblastoma phenotype contains a somatic PIK3CA mutation.

Lipoblastoma typically occurs in childhood and is associated with rearrangements of the PLAG1 gene. We present a patient with an isolated mass thought to be a lipoblastoma clinically, radiographically, and histologically. The lesion was diagnosed as a PIK3CA-adipose lesion after the tissue was negative for PLAG1 rearrangement and contained a somatic PIK3CA mutation (H1047R). Although PIK3CA variants are associated with PROS (PIK3CA-related overgrowth spectrum), this report illustrates a non-syndromic, lipoblastoma phenotype caused by a PIK3CA mutation.

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.

Cardiac lipoblastoma of the pulmonary valve: A rare tumor in an unusual location.

BACKGROUD: Lipoblastoma is a rare, benign, fatty tissue tumour tumor that occurs in infancy and early childhood. Intrathoracic and mediastinal involvement of this tumour is rare, and an intracardiac location is even rarer. AIMS: To report the first case of a lipoblastoma in the pulmonary valve. MATERIALS: In this study, we report the case of a 15-month-old girl who presented with a tumour in the pulmonary valve. RESULTS: The tumour was completely resected macroscopically. Histological examination of the lesion confirmed the diagnosis of lipoblastoma. DISCUSSION: Most primary cardiac tumours are benign in the sense they are not invasive. However, benign tumours maintain the potential for serious illness related to significant haemodynamic compromise or life-threatening dysrhythmias. Due to the association of lipoblastoma with other heart malformations, preoperative diagnosis remains challenging. CONCLUSION: Tumours on the heart valve are more likely to cause haemodynamic disturbances. Complete resection yields an excellent prognosis.

Follow-up outcomes of pediatric patients who underwent surgical resection for lipoblastomas or lipoblastomatosis: a single-institution experience with a systematic review and meta-analysis.

PURPOSE: The objective of this study was to examine the long-term outcomes of pediatric patients who underwent surgical resection for lipoblastoma and lipoblastomatosis (LB/LBM). METHODS: A single-center retrospective study of pediatric patients with LB/LBMs seen between 1991 and 2015 was conducted. A systematic review, including studies published prior to late August 2018, was performed. Using a random effect meta-analysis, pooled weighted proportions and unadjusted odds ratios (OR) with 95% confidence intervals (CI) were calculated. RESULTS: The retrospective study included 16 patients, while the systematic review included 19 published studies consisting of 381 patients. Among 329 (82%) patients with follow-up information, the pooled recurrence rate was 16.8% (95% CI 10.9-23.5%; I2 = 59%). The reported time to recurrence ranged from < 1 to 8 years. Recurrence risk was greater for incomplete (n = 34) than complete resection (n = 150): OR 11.4 (95% CI 3.0-43.6; I2 = 43%). LBMs (n = 35) had a greater recurrence risk than LBs (n = 116): OR 5.5 (95% CI 1.9-15.9; I2 = 0%). Recurrences were higher for studies with approximately ≥ 3 years of follow-up versus studies with < 3 years of follow-up. CONCLUSION: Recurrences are more likely to occur with LBMs and/or incomplete resection. Follow-up beyond 3-5 years should be considered given that the recurrence risk appears to be greater in the long-term.

Mediastinal lipoblastoma in paediatrics. / Lipoblastoma mediastínico en pediatría.

OBJECTIVE: To describe two cases of mediastinal lipoblastoma, an infrequent and little-known patho logy, which is extremely rare in the mediastinum, with no cases reported in our country. CLINICAL CASES: Two case reports. Both patients were boys younger than three years, in which a mediastinal mass was found incidentally on a chest x-ray. The study was complemented with a CT scan and with a thoracoscopic biopsy in one of the cases. Complete resection of the tumor was achieved in both patients through thoracotomy. One of the patients presented Claude Bernard Horner syndrome as a complication from surgery, which resolved spontaneously after two years and the second case had no complications. CONCLUSION: Mediastinal lipoblastoma is a very rare pathology. Descriptions found in existing literature are similar to the cases presented in this article. We can conclude that mediastinal lipoblastomas in pediatrics present a very similar pattern and presentation, having a good prognosis if complete resection is achieved. Also, it is essential to distinguish it from its differential diagnoses in order to rule out malignancy.

[Multivisceral resection of lipoblastoma of four anatomical areas of the head and neck with simultaneous neurotization of the facial muscles in an 8-months child. Clinical case]. / Polivistseral'naya rezektsiya lipoblastomy chetyrekh anatomicheskikh oblastei golovy i shei s odnomomentnoi nevrotizatsiei myshts litsa u rebenka 8 mesyatsev. Klinicheskii sluchai.

The article describes diagnostics and surgical treatment of a rare benign tumor (lipoblastoma) of four anatomical areas of the head and neck in an 8-months child. Diagnostic data, surgical procedure performed using microsurgical techniques and intraoperative neuromonitoring and the patient's condition in the long-term postoperative period are presented. The histological conclusion about the removal of the tumor with negative resection margins suggests favorable prognosis of the disease.

Identification of a novel BOC-PLAG1 fusion gene in a case of lipoblastoma.

Lipoblastoma is a rare benign adipose tissue tumor that occurs mostly in infants and children. Histological diagnosis of lipoblastoma is sometimes difficult because it closely resembles other lipomatous tumors. The detection of PLAG1 gene rearrangement is useful for the diagnosis of lipoblastoma. Four PLAG1 fusion partner genes are known in lipoblastoma: HAS2 at 8q24.1, COL1A2 at 7q22, COL3A1 at 2q32, and RAB2A at 8q12. Herein, we describe a novel fusion gene in a case of lipoblastoma of left back origin. We identified a potential PLAG1 fusion partner using 5' rapid amplification of cDNA ends, and sequence analysis revealed the novel fusion gene, BOC-PLAG1. The BOC-PLAG1 fusion transcript consists of the first exon of the BOC gene fused to exon 2 or exon 3 of the PLAG1 gene. PLAG1 expression was found to be 35.7 ±â€¯2.1 times higher in the tumor specimen than in human adipocytes by qRT-PCR. As a result of the translocation, the constitutively active promoter of BOC leads to PLAG1 overexpression. The identification of the BOC-PLAG1 fusion gene will lead to more accurate diagnosis of lipoblastoma.

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.

Myxoid Lipoblastoma and Mimickers on Fine-Needle Biopsy in a Child.

Image-guided percutaneous core needle biopsy is a standard and safe procedure for the diagnosis of both solid and hematological malignancies in children. Despite recent improvements, nondiagnosis biopsies persist. Lipoblastoma is a benign adipocytic tumor composed of embryonal fat admixed with mature adipocytes and occurring before the age of 1 year in one-third of cases. Lipoblastoma is usually easily diagnosed, but in some cases, diagnosis may be difficult on percutaneous biopsies, when the lipoblastic component is not well represented or when the tumor contains a prominent myxoid component mimicking other myxoid tumors. We report here a case of lipoblastoma with a predominant myxoid component and discuss differential diagnosis of myxoid lesions of infancy. In such cases, pathologic examination enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic studies, is needed to achieve accurate diagnosis, particularly on fine-needle biopsies.

[Myxoid lipoblastoma:a clinicopathological study of four cases].

Objective: To study clinicopathological features,diagnosis and differential diagnosis of myxoid lipoblastoma. Methods: Four cases of myxoid lipoblastoma, from 2010 to 2017 at Wuxi People's Hospital of Nanjing Medical University, the Affiliated Hospital of Xuzhou Medical University and Binhai People's Hospital, were studied by clinicopathological analysis, immunohistochemistry and in situ hybridization along with a literature review. Results: The age of the patients ranged from 1 to 6 years. Histologically, all tumors had thin fibrous capsule and irregular lobules separated by fibrous septa. The individual lobules consisted of myxoid stroma,prominent plexiform capillary network and stellate or spindle mesenchymal cells. Lipoblasts (S-100 positive) and mature adipocytes varies among different lobules. FISH revealed PLAG1 disruption in all 4 cases. MDM2 or CHOP alterations were not detected. None of the patients had tumor recurrence upon follow up from 12 to 80 months. Conclusions: Myxoid lipoblastoma is a very rare tumor, usually in the first 5 years of life. The clinical features of myxoid lipoblastoma and lipoblastoma are similar, while myxoid lipoblastoma has prominent myxoid change, a plexiform vascular pattern and rare mature fat cells. The patient age,S-100 positive lipoblasts and cytogenetic alteration are the key diagnostic features.