Molecular pathology of ADIPOCYTIC TUMORS – based on WHO 2020 Soft tissue and bone tumors.

LIPOMAS

The pathogenesis of lipomas is related to reactivated expression of the HMGA2 protein, which plays a role in the development of the mesodermal lineage during embryogenesis

1. ANGIOLIPOMA– The majority (80%) have been reported to have low-frequency PRKD2 mutations.
2. CHONDROID LIPOMA– is characterized by a recurrent t(11;16) (q13;p13) chromosomal translocation.
3. SPINDLE CELL/PLEOMORPHIC LIPOMA: is characterized 13q deletions /RB GENE.
4. MYOLIPOMA: Cytogenetic alterations of the HMGA2 gene have been reported in a few cases

LIPOSARCOMA

1. Atypical lipomatous tumour/well differentiated liposarcoma: characterized by supernumerary ring and giant marker chromosomes,containing amplified sequence of MDM2
2. DEDIFFERENTIATED liposarcoma– Amplified MDM2
3. MYXOID LIPOSARCOMA– Translocations producing FUS-DDIT3 or rarely EWSR1-DDIT3 fusion transcripts are pathognomonic
4. PLEOMORPHIC LIPOSARCOMA: Complex karyotypes. . The most frequent mutations involve TP53 and NF1.

OTHER ADIPOCYTIC TUMORS

1. HIBERNOMA: Cytogenetically, almost all hibernomas have breakpoints in chromosome arm 11q, with a distinctive clustering to 11q13.
2. LIPOBLASTOMA: The most common numerical change is one or more extra copies of chromosome 8, with or without concurrent rearrangement of 8q11-q13

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