Discordance Between the Initial Diagnosis of Sarcomas and Subsequent Histopathological Revision and Molecular Analyses in a Sarcoma Reference Center in Brazil.

PURPOSE: To investigate the discordance in sarcoma diagnoses between nonspecialized institutions following revision by dedicated sarcoma pathologists at a reference center in Brazil and the relevance of molecular pathology in this context. METHODS: We conducted a retrospective analysis of sarcoma samples initially analyzed at outside laboratories and subsequently reviewed by two specialized pathologists between January 2014 and December 2020. After obtaining demographic and tumor characteristics, pathology results were matched and classified as complete discordance (CD; benign v malignant, sarcoma v other malignancies), partial concordance (similar diagnosis of connective tumor, but different grade/histological subtype/differentiation), and complete concordance (CC). The concordance for histology or grade, and the role of molecular assessments supporting the diagnosis were also independently determined. Statistical analyses were conducted through the kappa coefficient of agreement and adherence by χ2 test, χ2 test by Person, and Fisher exact test. RESULTS: In total, 197 cases were included, with samples obtained predominately from male patients (57.9%) and localized/primary tumors (86.8%). Following revision, the most frequent final diagnoses were undifferentiated pleomorphic sarcoma (17.8%), well-differentiated/dedifferentiated liposarcoma (8.6%), and leiomyosarcoma (7.6%). CD was found in 13.2%, partial discordance in 45.2%, and CC in 41.6% of reviews (P < .001). We found a concordance for histology or grade of 53.5% (P < .001) and 51.8% (P < .001), respectively. Molecular assessments, comprising next-generation sequencing panels (79.5%) and fluorescent in situ hybridization (20.5%), were performed in 44 (22.3%) cases, with findings classified as of diagnostic relevance in 31.8%. CONCLUSION: In nearly 60% of the cases, the initial sarcoma diagnosis was modified when revised by a reference center and dedicated pathologists, assisted by molecular pathology techniques. These results justify the assembly of referral networks in countries with limited health care resources.

Breakpoint characterization of a novel large intragenic deletion of MUTYH detected in a MAP patient: case report.

BACKGROUND: MUTYH-associated polyposis (MAP) is a recessive, hereditary, colorectal cancer-predisposing syndrome caused by biallelic mutations in the MUTYH gene. Most MUTYH pathogenic variants are missense mutations, and until recently no gross genomic deletions had been described. CASE PRESENTATION: We have identified a large deletion in the MUTYH gene: a > 4.2 kb deletion encompassing exons 4-16. This is the second description of this rearrangement, which has been recently described as the first large deletion in this gene. The clinically suspected MAP patient was homozygous for this mutation and presented with no amplification products for 14 exons of MUTYH on initial screening. Deletion breakpoints were refined to base pair level through array comparative genomic hybridization (aCGH) analysis followed by sequencing. The identified breakpoints were located within intron 3 and 146 bp downstream of the 3' end of the gene, with the presence of an AluJr element adjacent to the distal breakpoint. The presence of a 2 bp insertion at the junction suggests the involvement of the non-homologous end joining (NHEJ) repair mechanism, possibly facilitated by rearrangement-promoting elements. Examination of the MUTYH locus revealed a high Alu density that may make this region prone to rearrangements. CONCLUSION: Large deletions are a possible mechanism for loss of function of the MUTYH gene, and investigation of such mutations may be important in identifying causative mutations in MAP patients.