A Primary Telangiectatic Mandibular Osteosarcoma With Germ-Line Malignancy-Associated DNA Damage Repair Gene Polymorphisms: A Case Report

Primary mandibular telangiectatic osteosarcomas are very rare lesions, with only nine cases reported. Histologically, these lesions show multiple cystic blood-filled cavities traversed by neoplastic bone in septa lined by high-grade malignant cells. Here, we report an 81-year-old woman who presented with a mandibular mass, which was surgically resected and analyzed by histologic examination and whole exome DNA sequencing. A diagnosis of telangiectatic osteosarcoma was given. Comparative sequencing data analysis of paired benign and tumor DNA revealed 1577 variants unique to the tumor DNA, which clustered into several gene families, including those regulating DNA repair and apoptosis. Comparison of benign and tumor DNA revealed many shared gene polymorphisms associated with an increased cancer risk. These included polymorphisms in the ATM, p53, BRCA1, and BRCA2 and many other genes. Interestingly, the patient's family history showed an unusually high cancer incidence, likely related to these cancer risk–associated polymorphisms. To our knowledge, this is the first-time sequencing applied to a mandibular telangiectatic osteosarcoma. Our findings may shed light on the molecular origins of these rare tumors and how they may relate to other tumors in related kindreds.


Introduction
Osteosarcomas are primary bone tumors composed of malignant mesenchymal osteoblast-like cells which produce a disorganized osteoid and/or bone matrix and whose growth depends on tumor-type specific cancer stem cells [1,2].Interestingly, they are the earliest identified human cancers and have been found in a 1.7-million-year-old hominin fossil from South Africa and in 77-million-year-old dinosaur bones [3,4].Osteosarcomas are classified based on anatomic location (axial/appendicular, central/surface), histologic grade, and the predominant matrix component; osteoblastic; chondroblastic; or fibroblastic.Uncommon osteosarcoma subtypes include surface osteosarcomas (parosteal and periosteal) and the telangiectatic subtype [1,2].

Case Report
An 81-year-old woman presented with temporal region headaches, right mandibular pain, and a slowly growing right mandibular lesion.The patient's past medical history included hypertension, type II diabetes, stroke, and hyperlipidemia.Positron emission tomography/computed tomography imaging revealed an exophytic mass, measuring 5 0 × 4 0 cm (Figure 1).The patient underwent a right segmental mandibulectomy, and the removed specimen measured 10 0 × 6 5 × 6 5 cm and weighed 144 g.The specimen contained soft tissue and skeletal muscle adherent to the mandible, and the mucosal surface was markedly distorted by multiple soft to firm, tan, exophytic nodules, the largest of which measured 3 5 × 3 1 × 2 5 cm (Figure 2).Hematoxylin and eosin-stained sections of the tumor revealed pleomorphic epithelioid cells in a matrix containing osteoid, numerous blood-filled spaces lined by pleomorphic epithelioid cells, with occasional giant cell formation and abnormal mitoses (Figure 3).A diagnosis of moderately differentiated mandibular telangiectatic osteosarcoma with lymphovascular invasion, without lymph node involvement, was rendered, stage pT1, pN0, pathologic stage group IA.Interestingly, the patient's family history revealed a high incidence of cancer in her paternal relatives, including a father with lung cancer; three paternal uncles with colon cancer, oral cancer, or melanoma; a paternal aunt with uterine cancer, leukemia, and a brain tumor; and a paternal grandmother who had uterine cancer.Additionally, the patient's 40-year-old son had melanoma (Figure 4).
Based on the rarity of this tumor and the high cancer incidence in the patient's family, DNA sequencing of the patient's tumor and benign tissue DNA was performed.Tumor and nontumor (benign parotid tissue) DNA samples were collected from the specimen (Figure 2).Tissue was taken for sequencing analysis prior to formalin fixation.The DNA was extracted and examined by Agilent TapeStation 2200.The DNA size distribution ranged from 600 bp to over 45 kb with a peak at 16 kb.The DNA library was prepared using Illumina's Nextera Rapid Capture Expanded Exome Kits.Pair end sequencing was performed at 2 × 76 on Illumina's NextSeq 500 system with Mid Output Kit (150 cycles).FASTQ files were generated by BaseSpace Onsite System.Read alignment and variant call analyses were completed by BWA Enrichment (BaseSpace Onsite System, Illumina) and visualized with Illumina Variant Studio.The quality filter was applied to remove variant calls with low quality.In the tumor DNA, we identified 43,106 single nucleotide variations, 1849 insertions, and 2185 deletions.Seven thousand eight hundred thirty-seven single nucleotide variations were missense variants.Sixty-six deletions and 36 insertions were inframe variants.Comparative analysis between tumor and nontumor DNA disclosed that 1577 predicted deleterious variants were unique to the tumor sample.These variants were seen in coding region, intron, and 3 ′ or 5 ′ UTR regions.Among 1577 variants, 801 variants were seen in coding region only, resulting in missense and frame shift mutation, in which 266 variants were homozygous mutations.Some mutants clustered in several gene families, including the mucin (MUC4, MUC6, MUC17, and MUC20), HLA (HLA-A, HLA-B, HLA-C, HLA-DQA, HLA-DQB, and HLA-DBR), zinc finger (ZNF221, ZNF417, ZNF517, ZNF595, ZNF774, and ZNF831), cytochrome p450 (CYP2A7, CYP27C1), DNA repair (GADD45B, MSH4, and TDG), and cell cycle regulating gene families (MCM4, RBBP8NL, PER3, CDK11B, CDC27, CCNE1, and TP53).
In addition to the unique variants in tumor DNA, multiple missense variants in DNA damage/repair-related genes were identified in both the benign and tumor DNAs.These variants may affect DNA repair functions in base excision repair, strand break joining, repair of DNA-topoisomerase crosslinks, mismatch excision repair, nucleotide excision repair, nonhomologous end joining, and homologous recombination.Some of the variants found are listed in Table 1.These shared common variants between benign and tumor DNA indicate that these are constitutional germline variations (polymorphisms) of the patient.

Case Reports in Oncological Medicine
Sequencing of the tumor DNA revealed mutations clustered in the mucin (MUC4, MUC6, MUC17, and MUC20), HLA (HLA-A, HLA-B, HLA-C, HLA-DQA, HLA-DQB, and HLA-DBR), zinc finger (ZNF221, ZNF417, ZNF517, ZNF595, ZNF774, and ZNF831), cytochrome p450 (CYP2A7, CYP27C1), DNA repair (GADD45B, MSH4, and TDG), and cell cycle regulating gene families (MCM4, RBBP8NL, PER3, CDK11B, CDC27, CCNE1, and TP53).Genes within these families have all been found to be mutated/dysregulated on osteosarcomas, with TP53, MUC4, MUC6, MUC17, TDG, MCM4, PER3, CDC27, and CCNE1 mutation/dysregulation having specifically been previously identified in osteosarcomas [15,[19][20][21][22][23][24][25][26].Thus, our sequencing results match previous findings and give a detailed molecular analysis of a very rare osteosarcoma subtype.Additionally, the patient's family had an extensive cancer history descended from the patient's paternal grandmother (Figure 4).Comparison of the tumor and benign tissue sequencing revealed many shared gene polymorphisms that conferred an increased cancer risk (Table 1).Thus, the patient's family history of extensive cancer is likely related to these many shared cancer risk-associated gene polymorphisms.Taken together, we present a 10th case of a mandibular telangiectatic osteosarcoma and its sequencing results.We also present data on how cancer risk gene polymorphisms may affect specific individual and associated kindred.Further research will be needed to identify how multiple cancer risk-associated gene polymorphisms give rise to specific tumor types.

Figure 2 :
Figure 2: Intraoperative clinical photographs.(a) Surgical defect following composite segmental mandibulectomy with condylar disarticulation via lip split.(b) Surgical defect with mandibular reconstruction plate with alloplastic condylar prosthesis in place.(c) Anterolateral thigh flap in place for soft tissue reconstruction.Photograph of gross specimen (arrow, mandibular condyle).

Figure 3 :
Figure 3: High-power view of hematoxylin and eosin-stained section of the telangiectatic osteosarcoma.The black arrows show osteoid formation.The white arrow shows a blood-filled cyst, typical of this lesion.The tumor stroma is dominated by highly pleomorphic osteoid-producing malignant mesenchymal cells (green arrows).

FatherFigure 4 :
Figure 4: A diagram of the patient's family tree showing an increased cancer incidence descended from the patient's paternal grandmother.Women are depicted with black circles and men with white squares.

Table 1 :
A list of some of the increased cancer risk-associated germline polymorphisms identified the patient's benign and tumor DNA.The COSMIC (Catalog of Somatic Mutations in Cancer) Program was employed to identify the malignancy types associated with each polymorphism.