Two forms of the tumor lesion have been described: encapsulated circumscribed type (lipoblastoma), and a noncapsulated diffuse infiltrative type (lipoblastomatosis).

Develops from embryonic remnants of white fat tissue.

Primarily occurs in young children (

Presents in superficial tissues of arms and legs (deeper in lipoblastomatosis), though mediastinum, retroperitoneum, trunk, head and neck may be affected.

Lobulated tissue composed of immature fat cells separated by fibro-vascular septa and areas with a myxoid matrix. The lobules contain lipoblasts in different stages of differentiation, ranging from primitive, spindle-shaped cells to lipoblasts simulating mature fat cells. Differential diagnosis, particularly in older children or in diffuse lipoblastoma, include myxoid liposarcoma and atypical lipoma and may be based on distinct cytogenetic abnormalities.

Surgical excision.

These tumors have an excellent prognosis but local recurrence is possible expecially in diffuse lesions.

Pseudodiploid karyotype with clonal chromosomal rearrangements involving the 8q11-13 region. Gain of chromosome 8 is reported.

Detectable by metaphase and/or interphase FISH using specific PLAG1 probes.

RP11-140I16, BAC227k20, YAC164H5, RP11-299N14, YAC947h7.

PLAG1 (Pleomorphic adenoma gene 1)

8q12.1

7313 bp mRNA

PLAG1, (together with PLAGL1 and PLAGL2), belongs to a subfamily of C2H2 zinc finger transcription factors that activate transcription.

HAS2 (hyaluronan synthase 2)

8q24.13

COL1A2 (collagen, type I, alpha 2)

7q21.3

HAS2-PLAG1, COL1A2-PLAG1 Chromosomal rearrangements in tumor tissue determine PLAG1 transcriptional up-regulation.

5 COL1A2 - 3 PLAG1 has been described in one case of t(7;8)(p22;q13)

Alternative splicing variants which included or lacked PLAG1 exon 2.

HAS2-PLAG1 and COL1A2-PLAG1 both encode a full-lenght PLAG1 protein.