Low-grade Osteosarcomatous Dedifferentiation of an Atypical Lipomatous Tumor in a Pediatric Patient

• Published in: Pediatric and developmental pathology Vol. 23; no. 3; p. 240
• Main Authors: Kukull, Benjamin J, Khalighi, Mazdak A, Gundle, Kenneth R, Hansford, Barry G, Corless, Christopher L, Davis, Jessica L
• Format: Journal Article
• Language: English
• Published: United States 01.06.2020
• Subjects: Adolescent; Cell Dedifferentiation; Diagnosis, Differential; Female; Gene Amplification; Humans; Liposarcoma - diagnosis; Liposarcoma - genetics; Liposarcoma - pathology; Neoplasm Grading; Neoplasm Recurrence, Local - diagnosis; Neoplasm Recurrence, Local - genetics; Neoplasm Recurrence, Local - pathology; Osteosarcoma - diagnosis; Proto-Oncogene Proteins c-mdm2 - genetics; Soft Tissue Neoplasms - diagnosis; Soft Tissue Neoplasms - genetics; Soft Tissue Neoplasms - pathology; MDM2; liposarcoma; atypical lipomatous tumor; osteosarcoma
• ISSN: 1615-5742
• DOI: 10.1177/1093526619889130

Atypical and malignant lipomatous tumors are infrequent in the pediatric population. Within this uncommon cohort, the morphologically and genetically related spectrum of atypical lipomatous tumor/well-differentiated liposarcoma/dedifferentiated liposarcoma (ALT/WDL/DDLS) is markedly rare. Their shared characteristic molecular aberration is a genomic amplicon of a region of chromosome 12q, including the oncogenes and . We present an unusual case of a pediatric patient with an ALT, with recurrence after 2 years in the form of a bone-forming mass, radiologically and pathologically mimicking parosteal osteosarcoma, a tumor also molecularly characterized by amplification of and . However, with ample histologic sampling, a single focus of lipogenic differentiation was identified, thus representing the first near complete low-grade osteosarcomatous dedififferentation reported within ALT/WDL/DDLS and the first ever in pediatric patient. The case serves a reminder of a diagnosis differential and pitfalls within -amplified tumors.