Molecular genetic characterization of the 11q13 breakpoint in a desmoplastic fibroma of bone

Low-grade central fibroblastic osteosarcoma may be differentiated from its mimicker desmoplastic fibroma by genetic analysis

Background

We studied two cases of rare fibrous bone tumors, namely desmoplastic fibroma (DF) and low-grade central osteosarcoma (LGCOS) resembling desmoplastic fibroma (DF-like LGCOS). As the clinical presentation, imaging features and histopathology of DF and DF-like LGOS show much overlap, the objective of this study was to investigate the value of cytogenetic analysis, molecular pathology and immunohistochemistry in discrimination of these two mimickers.

Case presentation

A mutation in CTNNB (S45F) and nuclear beta-catenin immunostaining were observed in DF. DF-LGCOS had amplification of CDK4 and showed strong nuclear expression of CDK4 by IHC. Moreover, the karyotype of DF-LGCOS showed an interstitial heterozygous deletion of the long arm of chromosome 13 (q12q32), associated with loss of the RB1 tumor suppressor gene.

Conclusions

Karyotyping and molecular genetic analysis may contribute to a conclusive diagnosis.

The Hidden Genomic and Transcriptomic Plasticity of Giant Marker Chromosomes in Cancer

Genome amplification in the form of rings or giant rod-shaped marker chromosomes (RGMs) is a common genetic alteration in soft tissue tumors. The mitotic stability of these structures is often rescued by perfectly functioning analphoid neocentromeres, which therefore significantly contribute to cancer progression. Here, we disentangled the genomic architecture of many neocentromeres stabilizing marker chromosomes in well-differentiated liposarcoma and lung sarcomatoid carcinoma samples. In cells carrying heavily rearranged RGMs, these structures were assembled as patchworks of multiple short amplified sequences, disclosing an extremely high level of complexity and definitely ruling out the existence of regions prone to neocentromere seeding. Moreover, by studying two well-differentiated liposarcoma samples derived from the onset and the recurrence of the same tumor, we documented an expansion of the neocentromeric domain that occurred during tumor progression, which reflects a strong selective pressure acting toward the improvement of the neocentromeric functionality in cancer. In lung sarcomatoid carcinoma cells we documented, extensive "centromere sliding" phenomena giving rise to multiple, closely mapping neocentromeric epialleles on separate coexisting markers occur, likely due to the instability of neocentromeres arising in cancer cells. Finally, by investigating the transcriptional activity of neocentromeres, we came across a burst of chimeric transcripts, both by extremely complex genomic rearrangements, and cis/trans-splicing events. Post-transcriptional editing events have been reported to expand and variegate the genetic repertoire of higher eukaryotes, so they might have a determining role in cancer. The increased incidence of fusion transcripts, might act as a driving force for the genomic amplification process, together with the increased transcription of oncogenes.

Desmoid-type fibromatosis of the head and neck region in the paediatric population: a clinicopathological and genetic study of seven cases

AIMS

Desmoid-type fibromatosis (desmoid) is a locally aggressive (myo)fibroblastic lesion. It represents one of the more common fibrous tumours in children and adolescents. The head and neck region is more often involved than in adults.

METHODS AND RESULTS

We investigated the clinicopathological and genetic characteristics of seven paediatric desmoids at this anatomical site, including two cases of desmoplastic fibroma located in the mandible. There were two females and five males with an age range of 1.5-8 years. The sites of the soft tissue lesions were sinonasal (n = 4) and paramandibular (n = 1). All cases showed typical morphology and nuclear β-catenin expression. CTNNB1 gene sequencing, performed successfully in five cases, revealed mutations in three cases with one p.T41A (bone lesion), one p.S37A and one novel mutation, p.D32V (sinonasal soft tissue lesions). Six patients were treated by excision with positive margins in five cases. Follow-up, available for six patients (median 4 years), showed no evidence of disease in four cases, slow progression in one case, and recurrence with stable disease in the last case.

CONCLUSIONS

Our study provides evidence of genetic similarities in desmoid and desmoplastic fibroma. Additionally, we expanded the spectrum of mutations in CTNNB1 with one novel desmoid mutation.

Desmoplastic fibroma arising in the distal phalanx of the great toe: a case report

Desmoplastic fibroma (DF) of the bone is a rare locally aggressive tumor usually occurring in adolescents and young adults. These tumors most commonly occur in the mandibles and metaphyses of long bones but are extremely rare in small bones, often resulting in diagnostic problems. The occurrence of these tumors in the foot is especially limited. We report the clinical, radiographic, and histologic features of DF arising in the distal phalanx of the great toe and a review of the published data.

Maxillary desmoplastic fibroma with initial symptoms suggestive of sinusitis

Desmoplastic fibroma (DF) is a benign intra-osseous neoplasm characterized by the formation of abundant collagen fibers. It arises most commonly in the jaws and exhibits local aggressiveness and high recurrence rates after local resection. An uncommon case of expansive DF involving the right maxilla, maxillary sinus, and inferior orbital wall of a 49-year-old man whose initial symptoms were similar to acute sinusitis is presented, and the criteria for diagnosis and clinical management are discussed.