Ovarian cancer mutational processes drive site-specific immune evasion.

High-grade serous ovarian cancer (HGSOC) is an archetypal cancer of genomic instability1-4 patterned by distinct mutational processes5,6, tumour heterogeneity7-9 and intraperitoneal spread7,8,10. Immunotherapies have had limited efficacy in HGSOC11-13, highlighting an unmet need to assess how mutational processes and the anatomical sites of tumour foci determine the immunological states of the tumour microenvironment. Here we carried out an integrative analysis of whole-genome sequencing, single-cell RNA sequencing, digital histopathology and multiplexed immunofluorescence of 160 tumour sites from 42 treatment-naive patients with HGSOC. Homologous recombination-deficient HRD-Dup (BRCA1 mutant-like) and HRD-Del (BRCA2 mutant-like) tumours harboured inflammatory signalling and ongoing immunoediting, reflected in loss of HLA diversity and tumour infiltration with highly differentiated dysfunctional CD8+ T cells. By contrast, foldback-inversion-bearing tumours exhibited elevated immunosuppressive TGFß signalling and immune exclusion, with predominantly naive/stem-like and memory T cells. Phenotypic state associations were specific to anatomical sites, highlighting compositional, topological and functional differences between adnexal tumours and distal peritoneal foci. Our findings implicate anatomical sites and mutational processes as determinants of evolutionary phenotypic divergence and immune resistance mechanisms in HGSOC. Our study provides a multi-omic cellular phenotype data substrate from which to develop and interpret future personalized immunotherapeutic approaches and early detection research.

Molecular characterization of high-grade serous ovarian cancers occurring in younger and older women.

OBJECTIVES: To determine if the mutational landscapes and genomic features of homologous recombination DNA repair defects (HRD) vary between younger and older patients with high-grade serous ovarian cancer (HGSOC). METHODS: Younger and older women were defined as bottom and top age quartiles, respectively. HGSOCs from 15 younger (median 49 years, range 35-53) and 15 older women (median 72 years, range 70-87) were subjected to whole-exome sequencing (WES). For validation, HGSOC WES data were obtained from The Cancer Genome Atlas (TCGA), including 38 younger (median 45 years, range 34-50) and 30 older women (median 74 years, range 68-84). Mutational profiles, BRCA1/2 status, genomic HRD features, and for TCGA cases RNA-sequencing-based HRD transcriptomic signatures were assessed. RESULTS: In the institutional cohort, pathogenic germline BRCA1/2 mutations were more frequent in younger (5/15) than older women (0/15, p = 0.042). No somatic BRCA1/2 mutations were identified. HGSOCs from older patients preferentially displayed aging-related mutational signatures and, in contrast to younger patients, harbored CCNE1 amplifications (3/15, 20%). In the TCGA cohort, pathogenic germline BRCA1 (younger 8/38, older 0/30, p = 0.007) but not BRCA2 mutations (young 3/38, older 4/30, p = 0.691) were more frequent in younger patients. Again, no somatic BRCA1/2 mutations were identified. HGSOCs from younger women more frequently displayed genomic features of HRD (all, p < 0.05), a significant HRD gene-signature enrichment, but less frequently CCNE1 amplification (p = 0.05). Immunoreactive CLOVAR subtypes were more common in HGSOCs from younger women, and proliferative subtypes in HGSOCs from older women (p = 0.041). CONCLUSIONS: HGSOC patients diagnosed at an older age less frequently harbor pathogenic BRCA1 germline mutations and genomic features of HRD than younger women. Individualized treatment options, particularly pertaining to use of PARP inhibitors, in older women may be warranted.

Genomic profiling of primary and recurrent adult granulosa cell tumors of the ovary.

Adult-type granulosa cell tumor (aGCT) is a rare malignant ovarian sex cord-stromal tumor, harboring recurrent FOXL2 c.C402G/p.C134W hotspot mutations in 97% of cases. These tumors are considered to have a favorable prognosis, however aGCTs have a tendency for local spread and late recurrences, which are associated with poor survival rates. We sought to determine the genetic alterations associated with aGCT disease progression. We subjected primary non-recurrent aGCTs (n = 7), primary aGCTs that subsequently recurred (n = 9) and their matched recurrences (n = 9), and aGCT recurrences without matched primary tumors (n = 10) to targeted massively parallel sequencing of ≥410 cancer-related genes. In addition, three primary non-recurrent aGCTs and nine aGCT recurrences were subjected to FOXL2 and TERT promoter Sanger sequencing analysis. All aGCTs harbored the FOXL2 C134W hotspot mutation. TERT promoter mutations were found to be significantly more frequent in recurrent (18/28, 64%) than primary aGCTs (5/19, 26%, p = 0.017). In addition, mutations affecting TP53, MED12, and TET2 were restricted to aGCT recurrences. Pathway annotation of altered genes demonstrated that aGCT recurrences displayed an enrichment for genetic alterations affecting cell cycle pathway-related genes. Analysis of paired primary and recurrent aGCTs revealed that TERT promoter mutations were either present in both primary tumors and matched recurrences or were restricted to the recurrence and absent in the respective primary aGCT. Clonal composition analysis of these paired samples further revealed that aGCTs display intra-tumor genetic heterogeneity and harbor multiple clones at diagnosis and relapse. We observed that in a subset of cases, recurrences acquired additional genetic alterations not present in primary aGCTs, including TERT, MED12, and TP53 mutations and CDKN2A/B homozygous deletions. Albeit harboring relatively simple genomes, our data provide evidence to suggest that aGCTs are genetically heterogeneous tumors and that TERT promoter mutations and/or genetic alterations affecting other cell cycle-related genes may be associated with disease progression and recurrences.

Immunohistochemical assessment of HRAS Q61R mutations in breast adenomyoepitheliomas.

AIMS: Breast adenomyoepitheliomas (AMEs) are uncommon tumours. Most oestrogen receptor (ER)-positive AMEs have mutations in phosphoinositide 3-kinase (PI3K) pathway genes, whereas ER-negative AMEs usually harbour concurrent mutations affecting the HRAS Q61 hotspot and PI3K pathway genes. Here, we sought to determine the sensitivity and specificity of RAS Q61R immunohistochemical (IHC) analysis for detection of HRAS Q61R mutations in AMEs. METHODS AND RESULTS: Twenty-six AMEs (14 ER-positive; 12 ER-negative) previously subjected to massively parallel sequencing (n = 21) or Sanger sequencing (n = 5) of the HRAS Q61 hotspot locus were included in this study. All AMEs were subjected to IHC analysis with a monoclonal (SP174) RAS Q61R-specific antibody, in addition to detailed histopathological analysis. Nine ER-negative AMEs harboured HRAS mutations, including Q61R (n = 7) and Q61K (n = 2) mutations. Five of seven (71%) AMEs with HRAS Q61R mutations were immunohistochemically positive, whereas none of the AMEs lacking HRAS Q61R mutations (n = 17) were immunoreactive. RAS Q61R immunoreactivity was restricted to the myoepithelium in 80% (4/5) of cases, whereas one case showed immunoreactivity in both the epithelial component and the myoepithelial component. RAS Q61R immunohistochemically positive AMEs were associated with infiltrative borders (P < 0.001), necrosis (P < 0.01) and mitotic index in the epithelial (P < 0.05) and myoepithelial (P < 0.01) components. RAS Q61R IHC assessment did not reveal Q61K mutations (0/2). CONCLUSIONS: IHC analysis of RAS Q61R shows high specificity (100%) and moderate sensitivity (71%) for detection of HRAS Q61R mutations in breast AMEs, and appears not to detect HRAS Q61K mutations. IHC analysis of RAS Q61R may constitute a useful technique in the diagnostic workup of ER-negative AMEs.

KIT genetic alterations in breast cancer.

AIMS: Activating somatic mutations or gene amplification of KIT result in constitutive activation of its receptor tyrosine kinase, which is targetable in various solid tumours. Here, we sought to investigate the presence of KIT genetic alterations in breast cancer (BC) and characterise the histological and genomic features of these tumours. METHODS: A retrospective analysis of 5,575 BCs previously subjected to targeted sequencing using the FDA-authorised Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Targets (MSK-IMPACT) assay was performed to identify BCs with KIT alterations. A histological assessment of KIT-altered BCs was conducted, and their repertoire of genetic alterations was compared with that of BCs lacking KIT genetic alterations, matched for age, histological type, oestrogen receptor/HER2 status and sample type. RESULTS: We identified 18 BCs (0.32%), including 9 primary and 9 metastatic BCs, with oncogenic/likely oncogenic genetic alterations affecting KIT, including activating somatic mutations (n=4) or gene amplification (n=14). All KIT-altered BCs were of high histological grade, although no distinctive histological features were observed. When compared with BCs lacking KIT genetic alterations, no distinctive genetic features were identified. In two metastatic KIT-altered BCs in which the matched primary BC had also been analysed by MSK-IMPACT, the KIT mutations were found to be restricted to the metastatic samples, suggesting that they were late events in the evolution of these cancers. CONCLUSIONS: KIT genetic alterations are vanishingly rare in BC. KIT-altered BCs are of high grade but lack distinctive histological features. Genetic alterations in KIT might be late events in the evolution and/or progression of BC.

Neuroendocrine tumours of the breast: a genomic comparison with mucinous breast cancers and neuroendocrine tumours of other anatomic sites.

AIMS: Breast neuroendocrine tumours (NETs) constitute a rare histologic subtype of oestrogen receptor (ER)-positive breast cancer, and their definition according to the WHO classification was revised in 2019. Breast NETs display histologic and transcriptomic similarities with mucinous breast carcinomas (MuBCs). Here, we sought to compare the repertoire of genetic alterations in breast NETs with MuBCs and NETs from other anatomic origins. METHODS: On histologic review applying the new WHO criteria, 18 breast tumours with neuroendocrine differentiation were reclassified as breast NETs (n=10) or other breast cancers with neuroendocrine differentiation (n=8). We reanalysed targeted sequencing or whole-exome sequencing data of breast NETs (n=10), MuBCs type A (n=12) and type B (n=11). RESULTS: Breast NETs and MuBCs were found to be genetically similar, harbouring a lower frequency of PIK3CA mutations, 1q gains and 16q losses than ER-positive/HER2-negative breast cancers. 3/10 breast NETs harboured the hallmark features of ER-positive disease (ie, PIK3CA mutations and concurrent 1q gains/16q losses). Breast NETs showed an enrichment of oncogenic/likely oncogenic mutations affecting transcription factors compared with common forms of ER-positive breast cancer and with pancreatic and pulmonary NETs. CONCLUSIONS: Breast NETs are heterogeneous and are characterised by an enrichment of mutations in transcription factors and likely constitute a spectrum of entities histologically and genomically related to MuBCs. While most breast NETs are distinct from ER-positive/HER2-negative IDC-NSTs, a subset of breast NETs appears to be genetically similar to common forms of ER-positive breast cancer, suggesting that some breast cancers may acquire neuroendocrine differentiation later in tumour evolution.

Cancer-Causative Mutations Occurring in Early Embryogenesis.

Mosaic mutations in normal tissues can occur early in embryogenesis and be associated with hereditary cancer syndromes when affecting cancer susceptibility genes (CSG). Their contribution to apparently sporadic cancers is currently unknown. Analysis of paired tumor/blood sequencing data of 35,310 patients with cancer revealed 36 pathogenic mosaic variants affecting CSGs, most of which were not detected by prior clinical genetic testing. These CSG mosaic variants were consistently detected at varying variant allelic fractions in microdissected normal tissues (n = 48) from distinct embryonic lineages in all individuals tested, indicating their early embryonic origin, likely prior to gastrulation, and likely asymmetrical propagation. Tumor-specific biallelic inactivation of the CSG affected by a mosaic variant was observed in 91.7% (33/36) of cases, and tumors displayed the hallmark pathologic and/or genomic features of inactivation of the respective CSGs, establishing a causal link between CSG mosaic variants arising in early embryogenesis and the development of apparently sporadic cancers. SIGNIFICANCE: Here, we demonstrate that mosaic variants in CSGs arising in early embryogenesis contribute to the oncogenesis of seemingly sporadic cancers. These variants can be systematically detected through the analysis of tumor/normal sequencing data, and their detection may affect therapeutic decisions as well as prophylactic measures for patients and their offspring. See related commentary by Liggett and Sankaran, p. 889. This article is highlighted in the In This Issue feature, p. 873.

Keratinocyte growth factor in focus: A comprehensive review from structural and functional aspects to therapeutic applications of palifermin.

Palifermin (Kepivance™) is the first therapeutic approved by the Food and Drug Administration for preventing and managing the oral mucositis provoked by myelotoxic and mucotoxic therapies. Palifermin is a recombinant protein generated from human keratinocyte growth factor (KGF) and imitates the function of endogenous KGF. KGF is an epithelial mitogen involved in various biological processes which belongs to the FGF family. KGF possesses a high level of receptor specificity and plays an important role in tissue repair and maintaining of the mucosal barrier integrity. Based on these unique features, palifermin was developed to enhance the growth of damaged epithelial tissues. Administration of palifermin has shown success in the reduction of toxicities of chemotherapy and radiotherapy, and improvement of the patient's quality of life. Notwithstanding all merits, the clinical application of palifermin is limited owing to its instability and production challenges. Hence, a growing number of ongoing researches are designed to deal with these problems and enhance the physicochemical and pharmaceutical properties of palifermin. In the current review, we discuss KGF structure and function, potential therapeutic applications of palifermin, as well as the latest progress in the production of recombinant human KGF and its challenges ahead.

Whole-exome sequencing analysis of juvenile papillomatosis and coexisting breast carcinoma.

Juvenile papillomatosis (JP) of the breast is a rare benign mass-forming lesion occurring in young women, which is histologically characterized by a constellation of proliferative changes and large cysts, giving it the gross appearance of Swiss cheese. A subset of patients with JP report a family history of breast carcinoma and/or coexisting or subsequent breast carcinoma. We performed whole-exome sequencing of the hyperplastic epithelial component of three JPs, including one with coexisting ductal carcinoma in situ (DCIS) and invasive ductal carcinoma of no special type (IDC-NST). JPs harbored clonal somatic PIK3CA hotspot mutations in two cases. In the JP with coexisting DCIS and IDC-NST, these lesions were clonally related to the associated JP, sharing a clonal PIK3CA E542K somatic hotspot mutation. JP showed a paucity of copy number alterations, whereas the associated DCIS and IDC-NST showed concurrent 1q gains/16q losses, hallmarks of estrogen receptor (ER)-positive breast cancers. We observed JP to harbor a dominant aging-related mutational signature, whereas coexisting DCIS and IDC-NST showed greater exposure to an APOBEC signature. Taken together, our findings suggest that, at least in a subset of cases, JP might constitute the substrate from which DCIS and invasive breast carcinomas develop.

TERT promoter hotspot mutations and gene amplification in metaplastic breast cancer.

Metaplastic breast cancers (MBCs) are characterized by complex genomes, which seem to vary according to their histologic subtype. TERT promoter hotspot mutations and gene amplification are rare in common forms of breast cancer, but present in a subset of phyllodes tumors. Here, we sought to determine the frequency of genetic alterations affecting TERT in a cohort of 60 MBCs with distinct predominant metaplastic components (squamous, 23%; spindle, 27%; osseous, 8%; chondroid, 42%), and to compare the repertoire of genetic alterations of MBCs according to the presence of TERT promoter hotspot mutations or gene amplification. Forty-four MBCs were subjected to: whole-exome sequencing (WES; n = 27) or targeted sequencing of 341-468 cancer-related genes (n = 17); 16 MBCs were subjected to Sanger sequencing of the TERT promoter, TP53 and selected exons of PIK3CA, HRAS, and BRAF. TERT promoter hotspot mutations (n = 9) and TERT gene amplification (n = 1) were found in 10 of the 60 MBCs analyzed, respectively. These TERT alterations were less frequently found in MBCs with predominant chondroid differentiation than in other MBC subtypes (p = 0.01, Fisher's exact test) and were mutually exclusive with TP53 mutations (p < 0.001, CoMEt). In addition, a comparative analysis of the MBCs subjected to WES or targeted cancer gene sequencing (n = 44) revealed that MBCs harboring TERT promoter hotspot mutations or gene amplification (n = 6) more frequently harbored PIK3CA than TERT wild-type MBCs (n = 38; p = 0.001; Fisher's exact test). In conclusion, TERT somatic genetic alterations are found in a subset of TP53 wild-type MBCs with squamous/spindle differentiation, highlighting the genetic diversity of these cancers.

Pleomorphic adenomas and mucoepidermoid carcinomas of the breast are underpinned by fusion genes.

Primary pleomorphic adenomas (PAs) and mucoepidermoid carcinomas (MECs) of the breast are vanishingly rare. Here we sought to determine whether breast PAs and MECs would be underpinned by the fusion genes reported to occur in their salivary gland counterparts. Our study included three breast PAs and one breast MEC, which were subjected to RNA sequencing (PAs, n = 2; MEC, n = 1) or to Archer FusionPlex sequencing (PA, n = 1). Our analyses revealed the presence of the HMGA2-WIF1 fusion gene in breast PA3, the CTNNB1-PLAG1 fusion gene in breast PA2, and the CRTC1-MAML2 fusion gene in the breast MEC analyzed (1/1). No oncogenic fusion genes were detected in breast PA1, and no additional oncogenic fusion genes were detected in the cases studied. The presence of the fusion genes identified was validated by fluorescence in situ hybridization (n = 1), reverse transcription-PCR (n = 1), or by both methods (n = 1). Taken together, our findings indicate that PAs and MECs arising in the breast resemble their salivary gland counterparts not only phenotypically but also at the genetic level. Furthermore, our data suggest that the molecular analysis of breast PAs and MECs might constitute a useful tool to aid in their differential diagnosis.

The genomic landscape of metastatic histologic special types of invasive breast cancer.

Histologic special types of breast cancer (BC) account for ~20% of BCs. Large sequencing studies of metastatic BC have focused on invasive ductal carcinomas of no special type (IDC-NSTs). We sought to define the repertoire of somatic genetic alterations of metastatic histologic special types of BC. We reanalyzed targeted capture sequencing data of 309 special types of BC, including metastatic and primary invasive lobular carcinomas (ILCs; n = 132 and n = 127, respectively), mixed mucinous (n = 5 metastatic and n = 14 primary), micropapillary (n = 12 metastatic and n = 8 primary), and metaplastic BCs (n = 6 metastatic and n = 5 primary), and compared metastatic histologic special types of BC to metastatic IDC-NSTs matched according to clinicopathologic characteristics and to primary special type BCs. The genomic profiles of metastatic and primary special types of BC were similar. Important differences, however, were noted: metastatic ILCs harbored a higher frequency of genetic alterations in TP53, ESR1, FAT1, RFWD2, and NF1 than primary ILCs, and in CDH1, PIK3CA, ERBB2, TBX3, NCOR1, and RFWD2 than metastatic IDC-NSTs. Metastatic ILCs displayed a higher mutational burden, and more frequently dominant APOBEC mutational signatures than primary ILCs and matched metastatic IDC-NSTs. ESR1 and NCOR mutations were frequently detected in metastatic mixed mucinous BCs, whereas PIK3CA and TP53 were the most frequently altered genes in metastatic micropapillary and metaplastic BCs, respectively. Taken together, primary and metastatic BCs histologic special types have remarkably similar repertoires of somatic genetic alterations. Metastatic ILCs more frequently harbor APOBEC mutational signatures than primary ILCs and metastatic IDC-NSTs.

Whole-Exome Sequencing Analysis of the Progression from Non-Low-Grade Ductal Carcinoma In Situ to Invasive Ductal Carcinoma.

PURPOSE: Ductal carcinoma in situ (DCIS) is a nonobligate precursor of invasive breast cancer. Here, we sought to investigate the level of intralesion genetic heterogeneity in DCIS and the patterns of clonal architecture changes in the progression from DCIS to invasive disease. EXPERIMENTAL DESIGN: Synchronous DCIS (n = 27) and invasive ductal carcinomas of no special type (IDC-NSTs; n = 26) from 25 patients, and pure DCIS (n = 7) from 7 patients were microdissected separately and subjected to high-depth whole-exome (n = 56) or massively parallel sequencing targeting ≥410 key cancer-related genes (n = 4). Somatic genetic alterations, mutational signatures, clonal composition, and phylogenetic analyses were defined using validated computational methods. RESULTS: DCIS revealed genetic alterations similar to those of synchronously diagnosed IDC-NSTs and of non-related IDC-NSTs from The Cancer Genome Atlas (TCGA), whereas pure DCIS lacked PIK3CA mutations. Clonal decomposition and phylogenetic analyses based on somatic mutations and copy number alterations revealed that the mechanisms of progression of DCIS to invasive carcinoma are diverse, and that clonal selection might have constituted the mechanism of progression from DCIS to invasive disease in 28% (7/25) of patients. DCIS displaying a pattern of clonal selection in the progression to invasive cancer harbored higher levels of intralesion genetic heterogeneity than DCIS where no clonal selection was observed. CONCLUSIONS: Intralesion genetic heterogeneity is a common feature in DCIS synchronously diagnosed with IDC-NST. DCIS is a nonobligate precursor of IDC-NST, whose mechanisms of progression to invasive breast cancer are diverse and vary from case to case.

Cytomegalovirus and Langerhans Cell Histiocytosis: Is There a Link?

BACKGROUND: Langerhans cell histiocytosis is a rare proliferative histiocytic disease of unknown etiology. Histologically, it is characterized by granuloma-like proliferation of Langerhans-type dendritic cells derived from bone marrow. Many investigators have suggested the possible role of viruses such as Epstein-Barr virus, human herpesvirus-6 (HHV-6), herpes simplex virus (HSV) types 1 and 2, and Cytomegalovirus in the pathogenesis of Langerhans cell histiocytosis. OBJECTIVES: In this study, we have investigated the presence of Cytomegalovirus in Langerhans cell histiocytosis in Iranian children. PATIENTS AND METHODS: In this retrospective study, we have investigated the presence of Cytomegalovirus DNA expression, using paraffin-embedded tissue samples of 30 patients with Langerhans cell histiocytosis and 30 age and site-matched controls by qualitative Polymerase Chain Reaction (PCR) method. RESULTS: No significant difference in prevalence of Cytomegalovirus presence between patients and controls was found. Cytomegalovirus was found by qualitative PCR in only 2 (6.66%) out of 30 patients and in 1 (3.3%) of 30 control samples with a P value of 1 (1.00 > 0.05) using chi-square test with OR: 2.07; 95% CI of OR: 0.18 - 24.15. CONCLUSIONS: Our findings do not support the hypothesis of a possible role for Cytomegalovirus in the pathogenesis of Langerhans cell histiocytosis.

Lack of BRAFV600E mutation in stage I and II of colorectal cancer.

AIM: We aimed to explore the frequency of BRAFV600E mutation in Iranian patients with colorectal cancer (CRC) as well as its association with clinic pathological characteristic of patients. BACKGROUND: CRC is the third leading cause of cancer related death. There is a growing body of data showing the association of BRAFV600E mutation with malignant transformation and clinical outcome of different tumors, including CRC. These findings suggest that BRAFV600E mutation can be used as diagnostic and/or prognostic biomarker for management of cancer patients. PATIENTS AND METHODS: A total of 85 patients with sporadic tumor were recruited. BRAFV600E mutation was investigated using sequencing of extracted DNAs from formalin-fixed paraffin-embedded (FFPE) tumor tissues. Electropherograms were analyzed using Laser-gene 6 software. RESULTS: More than 95% of patients were in stage I and II and none of them were in stage IV. Patients were mostly below 55 years old and tumors were dominantly located in the distal colon. Of note, no BRAFV600E mutations were detected in our population. CONCLUSION: Our results showed no V600E mutation in the BRAF gene in stage I and II of CRC patients. Further studies in multi-center settings are warranted to examine the prognostic and/or predictive value of this marker in different stages of colorectal cancer patients.

Detection of Epstein-Barr Virus DNA in Langerhans Cell Histiocytosis.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare histiocytic proliferation of unknown etiology. It is characterized by granuloma-like proliferation of Langerhans-type dendritic cells and mainly affects young children. Although multiple investigators have suggested the possible role of viruses, such as Epstein-Barr virus (EBV), human herpesvirus-6 (HHV-6), Herpes simplex virus (HSV) types 1 and 2, and Cytomegalovirus (CMV) in the pathogenesis of LCH, it remains, however, debated. OBJECTIVES: The EBV infection is reported to be associated with LCH. Nevertheless, no report could be found about involved Iranian children in English medical literature. In this study, we investigated the presence of EBV in Iranian children with LCH. PATIENTS AND METHODS: In this retrospective study, in which we investigated the prevalence of presence of EBV DNA in LCH, using paraffin-embedded tissue samples of 30 patients with LCH and 30 age and tissue-matched controls, who were operated for reasons other than infectious diseases (between the years 2002 and 2012), by real-time polymerase chain reaction (RT-PCR) method, in the department of pediatric pathology. No ethical issues arose in the study, because only the pathology reports were reviewed, retrospectively, and the patients were anonymous. RESULTS: There was a significant difference in prevalence of EBV presence between patients and controls. The EBV was found by RT-PCR in 19 (63.33%) out of 30 patients and only in eight (26.7%) of 30 control samples. The P = 0.004, was calculated using chi-square test (OR: 4.75; 95% CI: 1.58 ‒ 14.25). CONCLUSIONS: Our study is the first investigation performed on patients with LCH and its possible association with EBV in Iran. Considering the P = 0.004, which is statistically significant, the findings do support the hypothesis of a possible role for EBV in the pathogenesis of LCH. These results are in accordance with several previous investigations, with positive findings.