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Gross JM, Perret R, Coindre JM, Le Loarer F, Michal M, Michal M, Miettinen M, McCabe CE, Nair AA, Swanson AA, Thangaiah JJ, Torres-Mora J, Bonadio A, Voltaggio L, Epstein JI, Gupta S, Folpe AL, Schoolmeester JK. 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. Mod Pathol 2023; 36:100246. [PMID: 37307874 PMCID: PMC10530403 DOI: 10.1016/j.modpat.2023.100246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 06/01/2023] [Accepted: 06/06/2023] [Indexed: 06/14/2023]
Abstract
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.
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Affiliation(s)
- John M Gross
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Raul Perret
- Department of Biopathology, Institut Bergonié, Comprehensive Cancer Center, Bordeaux, France; Bordeaux Institute of Oncology, Université de Bordeaux, Institut Bergonié, Bordeaux, France
| | - Jean Michel Coindre
- Department of Biopathology, Institut Bergonié, Comprehensive Cancer Center, Bordeaux, France; Bordeaux Institute of Oncology, Université de Bordeaux, Institut Bergonié, Bordeaux, France; University of Bordeaux, Talence, France
| | - Francois Le Loarer
- Department of Biopathology, Institut Bergonié, Comprehensive Cancer Center, Bordeaux, France; Bordeaux Institute of Oncology, Université de Bordeaux, Institut Bergonié, Bordeaux, France; University of Bordeaux, Talence, France
| | - Michael Michal
- Department of Pathology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic
| | - Michal Michal
- Department of Pathology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic
| | - Markku Miettinen
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Chantal E McCabe
- Department of Quantitative Health Sciences, Division of Computational Biology, Mayo Clinic, Rochester, Minnesota
| | - Asha A Nair
- Department of Quantitative Health Sciences, Division of Computational Biology, Mayo Clinic, Rochester, Minnesota
| | - Amy A Swanson
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Judith J Thangaiah
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Jorge Torres-Mora
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Angelo Bonadio
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Lysandra Voltaggio
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Jonathan I Epstein
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Sounak Gupta
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Andrew L Folpe
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
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