Soft tissue
Adipose tissue tumors
Other benign lesions
Lipoblastoma / lipoblastomatosis
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Last author update: 20 December 2022
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PubMed Search: Lipoblastoma / lipoblastomatosis
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Cytology description | Cytology images | Positive stains | Negative stains | Molecular / cytogenetics description | Molecular / cytogenetics images | Videos | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Abdul-Ghafar J, Haidari M, Ud Din N. Lipoblastoma / lipoblastomatosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposelipoblastoma.html. Accessed April 26th, 2024.
Definition / general
- Benign, rapidly growing neoplasm composed of embryonal white fat with variable degrees of myxoid changes (Mod Pathol 2021;34:584, J Clin Med 2022;11:1938)
- Occurs predominantly in infancy, early childhood and very rarely in adulthood (J Clin Med 2022;11:1938)
- Lipoblastoma: superficial, localized, well circumscribed; complete excision easy; common type
- Lipoblastomatosis: deep, diffuse, irregular borders; complete excision difficult; rare type (J Clin Med 2022;11:1938)
Essential features
- Benign, rapidly growing neoplasm that is commonly superficial and well defined
- 75 - 90% are seen before the age of 3 years, with male predilection (M:F = 2.8:1)
- Mostly occurs in trunk and extremities
- Lobular architecture with intersecting fibrovascular septa, myxoid changes and a spectrum of fat cell maturation
- Positive stains are S100, CD34 (adipocytes and vascular network), desmin (mesenchymal cells)
Terminology
- Lipoblastoma: well circumscribed and superficial (J Clin Med 2022;11:1938)
- Lipoblastomatosis: deep seated with ill defined borders (J Clin Med 2022;11:1938)
- Not recommended: fetal lipoma, fetal fat tumor, fetocellular lipoma, embryonal lipoma, congenital lipomatoid tumor, lipoblastic tumor of childhood
ICD coding
- ICD-O: 8881/0 - lipoblastomatosis
- ICD-10: D17.9 - benign lipomatous neoplasm, unspecified
- ICD-11: 2E80.1 & XH8L55 - lipoblastoma / lipoblastomatosis
Epidemiology
- 18 - 20% of adipocytic tumors (J Int Med Res 2021;49:300060520981362)
- 75 - 90% are seen before 3 years of age (J Clin Med 2022;11:1938)
- Rarely in adulthood (J Clin Med 2022;11:1938)
- Most common in males (M:F = 2.8:1) (BMC Res Notes 2018;11:42)
- Can be associated with cleft lip, cleft palate, cephalic malformations and neurologic disorders (Exp Ther Med 2021;22:903)
Sites
- Common in trunk and extremities (Exp Ther Med 2021;22:903, BMC Res Notes 2018;11:42)
- Less common sites:
- Head and neck
- Abdomen and mesentery
- Retroperitoneum and pelvis
- Inguinoscrotal or labial region
- Perineum and mediastinum (Exp Ther Med 2021;22:903)
- Very rare sites: lung, liver, heart, colon and parotid gland (J Clin Med 2022;11:1938)
Pathophysiology
- Exhibits pseudodiploid or hyperdiploid karyotypes combined with structural alteration of 8q11-q13, which leads to PLAG1 rearrangement (J Clin Med 2022;11:1938)
- Numerical change in one or more extra copies of chromosome 8, with or without concurrent rearrangement of 8q11-q13 (J Clin Med 2022;11:1938)
Etiology
- Unknown at this time (Pediatr Hematol Oncol 2017;34:212)
Clinical features
- Rapidly growing, painless, soft tissue mass with swelling (BMC Res Notes 2018;11:42)
- Usually, the rapid growth of the mass causes the symptoms
- Colonic and mesenteric cases have been associated with intussusception and volvulus (BMC Res Notes 2018;11:42)
- Mediastinal or cervical tumors may appear with stridor (Cancer Imaging 2012;12:484)
- No metastasis recorded (Exp Ther Med 2021;22:903, J Clin Med 2022;11:1938)
Diagnosis
- Standard diagnostic approach is histopathologic examination with immunohistochemistry as an adjunct (Exp Ther Med 2021;22:903)
- FISH and RNA sequencing are also useful (Mod Pathol 2021;34:584)
- Radiologic findings alone cannot rule out malignancy (Turk Patoloji Derg 2020;36:1)
Radiology description
- Radiologic findings alone cannot rule out malignancy (Turk Patoloji Derg 2020;36:1)
- Ultrasound:
- Usually is the first imaging examination (Korean J Radiol 2020;21:341)
- Fluid collection, vascularity detection in color Doppler (Indian J Radiol Imaging 2021;31:710)
- Hyperechoic, admixed with the surrounding muscle tissue and parallel to the skin, as an elliptical or rounded mass lesion (Turk Patoloji Derg 2020;36:1)
- Xray (plan radiography):
- Only as a shadow of soft tissue
- Without calcification or specific features (J Med Case Rep 2017;11:338)
- Magnetic resonance imaging (MRI):
- Lobulated fatty mass with a variable amount of nonenhancing cystic area
- Internal fibrous partitions intermixed with enhancing soft tissue mass
- Difficult to differentiate from myxoid liposarcoma (J Med Case Rep 2017;11:338)
- Computed tomography (CT scan):
- Well limited lobulated mass, showing greasy density similar to that of subcutaneous fat
- Crossed by internal septa (Int J Surg Case Rep 2021;84:106050)
Radiology images
Contributed by Nasir Ud Din, M.B.B.S.
Lipomatous lesion with septations
Images hosted on other servers:
Circumscribed, lobulated hyperechoic mass
Localized mass of soft tissue, without calcification
T1 fat saturation (MRI)
Cervical mass, greasy density
Prognostic factors
- Favorable: well circumscribed, encapsulated (J Clin Med 2022;11:1938)
- Up to 80% chance of recurrence for incompletely resected tumors (BMC Res Notes 2018;11:42)
- Excellent prognosis after complete excision (J Clin Med 2022;11:1938)
Case reports
- 12 month old boy with bilateral inguinal masses (Urol Case Rep 2019;26:100961)
- 23 month old girl with a painless mass on popliteal side of her thigh (J Med Case Rep 2017;11:338)
- 3 year old boy with a right hemithorax mass and respiratory problems (Respir Med Case Rep 2019;26:200)
- 37 year old man with a right side intrascrotal mass (BMJ Case Rep 2019;12:e231320)
- 80 year old woman with a left kidney mass (Ann Transl Med 2019;7:150)
Treatment
- Complete surgical excision (BMC Res Notes 2018;11:42, J Clin Med 2022;11:1938)
- 5 year follow up is recommended (BMC Res Notes 2018;11:42)
- No metastasis has been reported (J Clin Med 2022;11:1938)
Clinical images
Images hosted on other servers:
Right lower leg mass
Intraoperative aspect of lipoblastoma
Gross description
- Typically 2 - 5 cm in diameter but can be > 10 cm (Pediatr Hematol Oncol 2017;34:212)
- Soft, lobulated, yellow, white or tan mass (J Clin Med 2022;11:1938)
- May display myxoid nodules, cystic spaces or adipose nodules separated by fine white fibrous septa on the cut surface (BMC Res Notes 2018;11:42)
Gross images
Contributed by Nasir Ud Din, M.B.B.S.
Round mass
Cut surface
Multilobulated mass
Microscopic (histologic) description
- Consists of lobulated sheets of adipocytes (J Clin Med 2022;11:1938, BMC Res Notes 2018;11:42)
- Myxoid areas with plexiform vascular network and primitive mesenchymal cells (J Clin Med 2022;11:1938, BMC Res Notes 2018;11:42, Pediatr Blood Cancer 2009;52:132)
- Fat cells revealing a spectrum of maturation, ranging from primitive stellate or spindled mesenchymal cells to multivacuolated or small signet ring cell lipoblasts (J Clin Med 2022;11:1938, BMC Res Notes 2018;11:42)
- Lobule zonation is defined by arrangement of immature myxoid cells at periphery near fibrous septa and mature adipocytes at center of the lobule (BMC Res Notes 2018;11:42, J Clin Med 2022;11:1938)
- Myxoid areas may rarely mimic myxoid liposarcoma due to pooling of myxoid matrix (Am J Surg Pathol 1997;21:1131)
- Mature parts are similar to lipoma or fibrolipoma (Mod Pathol 2021;34:584)
- Tumor with late resection may show fibrolipomatous changes with no presence of lipoblasts (Mod Pathol 2021;34:584)
- Other histological findings are chondroid metaplasia, extramedullary hematopoiesis, chronic inflammation and sparsely multinucleated or floret cells (J Clin Med 2022;11:1938)
Microscopic (histologic) images
Contributed by Nasir Ud Din, M.B.B.S.
Lobulation
Vasculature
Myxoid background
Lipoblasts in various stages
Lipoblasts and mesenchymal cells
Septation
Zonation
Primitive mesenchymal cells
Desmin IHC stain
CD34 IHC stain
Virtual slides
Images hosted on other servers:
Lipoblastoma / lipoblastomatosis
Cytology description
- Mixed population of lipoblasts and mature adipocytes (Cancer Cytopathol 2017;125:934)
- Myxoid background with a rich network of capillary vessels (Cancer Cytopathol 2017;125:934)
- May also show spindle cells and naked nuclei (Cancer Cytopathol 2017;125:934)
- Mostly no cytological atypia (Cancer Cytopathol 2017;125:934)
Cytology images
Images hosted on other servers:
Mature adipocytes and lipoblasts
Myxoid stromal with capillaries
Univacuolated and multivacuolated lipoblasts
Positive stains
- Adipocytes: S100, CD34 and CD56 (J Clin Med 2022;11:1938)
- Primitive mesenchymal cells: desmin (J Clin Med 2022;11:1938)
- Vascular endothelial cells: CD34 (BMC Res Notes 2018;11:42)
- Aberrant PLAG1 positivity (80%) (J Clin Med 2022;11:1938)
Negative stains
- MDM2, CDK4 and p16 (BMC Res Notes 2018;11:42)
Molecular / cytogenetics description
- Clonal rearrangements involving chromosomal region 8q11 > q13 (8q12) is the hallmark (BMC Res Notes 2018;11:42)
- Oncogene PLAG1 (pleomorphic adenoma gene 1) is located on band 8q12 (BMC Res Notes 2018;11:42)
- Other rare fusion partners of PLAG1 are COL1A2 (7q21.3), HAS2 (8q24.13), RAD51B (14q24.1), COL3A1 (2q32.2), RAB2A (8q12.1-q12.2) and BOC (3q13.2) (Mod Pathol 2021;34:584)
- Novel reported fusions are HNRNPC::PLAG1, SRSF3::PLAG1, PCMTD1::PLAG1, YWHAZ::PLAG1, CTDSP2::PLAG1 and PPP2R2A (Mod Pathol 2021;34:584)
Molecular / cytogenetics images
Images hosted on other servers:
PLAG1 RNA expression
Molecular confirmation of fusions
FISH / CISH of PLAG1 gene
Videos
Lipoblastoma histopathology
Sample pathology report
- Soft tissue, thigh, left, excisional biopsy:
- Benign adipocytic neoplasm with features favoring lipoblastoma (see comment)
- Tumor size: 7 x 6 x 4 cm
- Margins are free of tumor
- Comment: Histological examination shows an adipocytic neoplasm with a lobular architecture by intersecting fibrous septa and zonation along with myxoid areas. A spectrum of fat cell maturation, from primitive stellate to spindled mesenchymal cells, multivacuolated lipoblasts to mature fat cells are seen. Immunohistochemically, the tumor cells are showing positivity for S100 and CD34 and are negative for MDM2, CKD4 and p16. This constellation of morphological and immunohistochemical features strongly supports the diagnosis of lipoblastoma. This is a benign, rapidly growing soft tissue neoplasm prone to recur unless completely excised.
Differential diagnosis
- Pediatric lipoma:
- Does not show lipoblasts or primitive mesenchymal cells
- Not common in extremities
- Does not show chromosome 8 abnormalities (BMC Res Notes 2018;11:42)
- Hibernoma:
- Rare in children
- Brown fat cells that have a central nucleus and abundant finely granular cytoplasm
- 11q13 abnormalities (BMC Res Notes 2018;11:42)
- Pediatric myxoid liposarcoma:
- Very rare in children < 10 years old and always deeply situated
- Shows pools of stromal mucin (pulmonary edema pattern)
- Has hypercellular areas
- Shows nuclear atypia with no presence of lobulated growth
- Maturation of adipocytes occurs at periphery
- Does not show chromosome 8 abnormalities
- t(12;16) or t(12;22) (BMC Res Notes 2018;11:42)
- Atypical lipomatous tumor / well differentiated liposarcoma:
- Rare in children
- Atypical stromal cells and lipoblasts
- MDM2 and CDK4 are positive
- Majority are positive for p16 (J Clin Med 2022;11:1938)
Additional references
Board review style question #1
A 12 month old boy presents with a large, painless mass at lateral part of the left thigh. Excisional biopsy shows a well defined lobulated mass with fibrovascular septa, myxoid areas, aggregates of spindle cells and a mixture of mature and immature adipocytes. The adipocytic cells are positive for CD34 and CD56. The desmin is positive in spindle cells. The tumor cells are negative for MDM2 and p16. Which of the following is true regarding the above scenario?
- Adipocytic tumor with low malignant potential
- Findings are compatible with myxoid liposarcoma
- Radiological examinations are the main diagnostic tool
- The tumor cells are also positive for CKD4 IHC stain
- The tumor mainly exhibits PLAG1 rearrangement
Board review style answer #1
E. The tumor mainly exhibits PLAG1 rearrangement
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Reference: Lipoblastoma / lipoblastomatosis
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Board review style question #2
Which of the following is true about lipoblastoma / lipoblastomatosis?
- It is a highly infiltrative lesion, which leads the majority to recur
- It is common in women and complete resection is the treatment of choice
- It is the most common benign neoplasm with no chance of recurrence
- It usually appears as a superficial, round, lobulated mass with male predilection
- Negative CD34 IHC stain confirms the diagnosis of lipoblastoma
Board review style answer #2
D. It usually appears as a superficial, round, lobulated mass with male predilection
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