Folliculin Research Articles

Multinucleated tumor cells and micropapillary morphology appear to be predictors of poor prognosis in renal cell carcinoma with papillary and oncocytic features

Renal cell carcinoma with papillary and oncocytic features (RCC-PO) are poorly understood, partially due to conflicting results in multiple studies. The histological features that predict behavior of RCC-PO have not been elucidated. The aim is to review clinicopathologic features and to correlate clinical outcomes of patients with RCC-PO to further expand our knowledge on these heterogeneous tumors. An archival search was done for “RCC” and “papillary,” and tumors with >50% papillary and oncocytic features were included. Clinicopathologic data including tumor size, grade, stage, molecular and immunohistochemical testing when performed, and follow-up data were collected. Using multivariate analyses, correlation between histological features, tumor stage and prognosis were analyzed. Sixty-one patients with RCC-PO were identified of which 49 (80%) were male with a median age of 65 (range: 36–93) years, and a mean tumor size of 5.2 (range: 1–21.5) cm. Micropapillary features were seen in 4, bizarre nuclei (at least 3 times larger or with irregular shape) in 6, multinucleated tumor cells (MTC) in 15, single or small clusters (SSC) (made of 2–3 tumor cells) located away from areas of necrosis in 16, and striking eosinophilic cytoplasmic inclusions in 3 tumors, respectively. Thirty-six (59%) tumors were high-grade (WHO/ISUP grade 3–4), and 23 (38%) had a high stage (≥pT3 or pN1). Tumors were positive for AMACR (15/16) and CK7 (13/17), with preserved FH (7/7) staining and were all negative for CD117 (0/7), ALK, TFE3, cathepsin K, Melan A, and HMB45 (0/4, each). Three tumors underwent chromosomal microarray (CMA) plus gene fusion assay, and FISH and germline testing for FLCN and MET gene alterations by PCR were done on 1 each. Ten (16%) patients had a local recurrence (LR) or metastasis after nephrectomy; 4 died of disease (2 had tumors with micropapillary features), with a median follow-up of 7 (range: 0.01–19) years. Tumors with micropapillary features showed significantly higher RCC-PO-related mortality (50% vs. 3.5%, p < 0.001). In multivariable analysis, SSC correlated with a higher stage (HR: 11.95; p = 0.005); micropapillary features (HR: 18.42; p = 0.017) and MTC (HR: 180.22; p = 0.036) with presence of metastasis/LR; and micropapillary features with a higher RCC-PO-related mortality (HR: 60.35; p = 0.036). RCC-PO are cytogenetically heterogeneous with overlapping features of various renal neoplasms. Micropapillary features and MTC appear to be independent predictors of poor outcomes in these tumors.

Molecular Pathogenesis of Renal Neoplasms in Patients with Birt–Hogg–Dubé Syndrome

Birt–Hogg–Dubé syndrome (BHDS) is an autosomal dominant disease characterized by skin, lung, and renal manifestations. This syndrome is caused by a germline mutation in the FLCN gene, which leads to disruption in multiple downstream pathways. Renal cell carcinomas are one of the serious clinical manifestations of the disease, which usually presents as bilateral and multiple tumors. Morphologically, most of these tumors are classified as hybrid oncocytic tumors. Recent advances in molecular techniques have shed light on the pathogenesis of these renal tumors. In this review, we evaluate and summarize the current knowledge of BHDS, pathologic changes, and its molecular basis with the focus on the renal hybrid oncocytic tumor (HOT), their pathogenesis, and molecular underpinning.

ERN GENTURIS clinical practice guidelines for the diagnosis, surveillance and management of people with Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé syndrome (BHD syndrome) is an autosomal dominant multisystem disorder with variable expression due to pathogenic constitutional variants in the FLCN gene. Patients with BHD syndrome are predisposed to benign cutaneous fibrofolliculomas/trichodischomas, pulmonary cysts with an associated risk of spontaneous pneumothorax, and renal cell carcinoma. A requirement for updated International consensus recommendations for the diagnosis and management of BHD syndrome was identified. Based on a comprehensive literature review and expert consensus within the fields of respiratory medicine, urology, radiology, dermatology, clinical oncology and clinical genetics, updated recommendations for diagnosis, surveillance and management in BHD syndrome were developed. With the widespread availability of FLCN genetic testing, clinical scenarios in which a diagnosis should be considered and criteria for genetic testing were defined. Following a clinical and/or molecular diagnosis of BHD syndrome, a multidisciplinary approach to disease management is required. Regular renal cancer surveillance is recommended in adulthood and life-long, but the evidence base for additional tumour surveillance is limited and further research warranted. Recommendations for the treatment of cutaneous, pulmonary and renal manifestations are provided. Awareness of BHD syndrome needs to be raised and better knowledge of the clinical settings in which the diagnosis should be considered should enable earlier diagnosis. Further details, including areas for future research topics are available at: https://www.genturis.eu/l=eng/Guidelines-and-pathways/Clinical-practice-guidelines.html .

A novel variant in the FLCN gene in a Chinese family with Birt-Hogg-Dubé syndrome.

This study aimed to identify disease-causing variants within a Chinese family affected by Birt-Hogg-Dubé syndrome (BHDS), which arises from an autosomal dominant inheritance pattern attributed to variants in the folliculin (FLCN) gene, recognized as a tumor suppressor gene. A Chinese proband diagnosed with BHDS due to renal tumors underwent next-generation sequencing (NGS), revealing a novel variant in the FLCN gene. Sanger sequencing was subsequently performed on blood samples obtained from family members to confirm the presence of this variant. A novel germline frameshift variant (NM_144997.5:c.977dup) was identified in five individuals among the screened family members, marking the first report of this variant. Additionally, a somatic frameshift variant (NM_144997.5:c.1252del) was detected in the renal tumors of the proband. No variant was detected in unaffected family members. A novel heterozygous variant was identified in exon 9 of the FLCN gene, which broadens the spectrum of FLCN variants. We recommend that molecular analysis of the FLCN gene be performed in patients with suspected BHDS and their families.

Investigating the Impact of Birt–Hogg–Dubé Syndrome Associated Folliculin (FLCN) and Retinitis Pigmentosa 2 (RP2) Loss on Cilia Function and Morphology

Folliculin (FLCN), a GTPase-activating protein (GAP), has been linked to Birt–Hogg–Dubé syndrome, the mTORC1 signaling pathway and cilia. Disruptions in cilia structure and function lead to a group of diseases known as ciliopathies. Birt-Hogg-Dubé syndrome is one of 35 different ciliopathy diseases and there are more than 250 genes that cause ciliopathy diseases. FLCN interacts with kinesin-2 along cilia. The specific role of FLCN in regulating Kinesin-IFT trafficking has, however, remained unclear. In the current study, we investigated the effects of flcn-1 loss (the human ortholog of FLCN) on kinesin and IFT trafficking in C. elegans. The loss of flcn-1 alone did not result in any apparent alterations to kinesin or IFT trafficking within the cilia. However, when we combined the deletion of flcn-1 with the deletion of Retinitis Pigmentosa 2 (RP2), another GAP protein, the ciliary entry of a non-ciliary membrane protein TRAM-1 (Translocation Associated Membrane Protein 1) occured. Additionally, although cilia length was unaltered, our analysis of double mutants revealed the extra branch in wing AWB cilia morphology but not the single rod-like PHA/PHB cilia. In summary, our study reveals the previously unknown functions of FLCN in ciliary gating and cilia morphology in C. elegans

Characterizing the tumor suppressor activity of FLCN in Birt-Hogg-Dubé syndrome through transcriptiomic and proteomic analysis.

Birt-Hogg-Dubé (BHD) syndrome patients are uniquely susceptible to all renal tumour subtypes. The underlying mechanism of carcinogenesis is unclear. To study cancer development in BHD, we used human proximal kidney (HK2) cells and found that long-term folliculin (FLCN) knockdown was required to increase their tumorigenic potential, forming larger spheroids in non-adherent conditions. Transcriptomic and proteomic analysis uncovered links between FLCN, cell cycle control and the DNA damage response (DDR) machinery. HK2 cells lacking FLCN had an altered transcriptome profile with cell cycle control gene enrichment. G1/S cell cycle checkpoint signaling was compromised with heightened protein levels of cyclin D1 (CCND1) and hyperphosphorylation of retinoblastoma 1 (RB1). A FLCN interactome screen uncovered FLCN binding to DNA-dependent protein kinase (DNA-PK). This novel interaction was reversed in an irradiation-responsive manner. Knockdown of FLCN in HK2 cells caused a marked elevation of γH2AX and RB1 phosphorylation. Both CCND1 and RB1 phosphorylation remained raised during DNA damage, showing an association with defective cell cycle control with FLCN knockdown. Furthermore, Flcn-knockdown C. elegans were defective in cell cycle arrest by DNA damage. This work implicates that long-term FLCN loss and associated cell cycle defects in BHD patients could contribute to their increased risk of cancer.

A retrospective cohort study of genetic referral and diagnosis of Birt-Hogg-Dubé Syndrome in patients with Trichodiscoma and Fibrofolliculoma skin lesions.

Birt-Hogg-Dubé (BHD) syndrome is a genetic condition caused by pathogenic variants in the FLCN gene resulting in benign skin lesions, spontaneous pneumothorax, and increased risk for a variety of renal tumors. Skin manifestations of BHD include trichodiscoma (TD) and fibrofolliculoma (FF), which may represent the same pathologic entity. These lesions can identify BHD patients, who upon positive genetic testing can be considered for life-long surveillance for renal neoplasms. To characterize patients diagnosed with TD and FF including rates and outcomes of genetics referral. Retrospective chart reviews of patients with confirmed or possible diagnosis of TD or FF at the University of Michigan from September 2002 through October 2020 to assess pathologic findings, personal and family history of BHD manifestations, referral for genetic evaluation, and genetic testing results. 64 patients had a pathologic diagnosis of TD or FF, 16 of whom (25%) were referred to cancer genetics. Fourteen patients completed genetic evaluation, 9 of whom were diagnosed with BHD (64%), with 6 unique pathogenic variants in FLCN. Providers should consider referral for genetic evaluation for patients with biopsy-proven TD or FF, as early diagnosis of BHD provides the opportunity for early detection and treatment of other BHD-associated conditions.

P24 Folliculin silencing in human hair follicles ex vivo upregulates intrafollicular mechanistic target of rapamycin complex 1 activity: a new model for studying Birt–Hogg–Dubé syndrome

Abstract Introduction and aims Birt–Hogg–Dubé (BHD) syndrome is a rare multisystem disorder caused by germline pathogenic variants in the FLCN gene. BHD skin tumours predominantly affect facial skin, confer a significant psychosocial burden, and there is a lack of nonsurgical therapies. Here we report a novel ex vivo human model to study the impact of FLCN loss in human hair follicles (HFs), the putative origin of BHD skin tumours. Methods Organ-cultured human anagen HFs and scalp skin were treated with small interfering RNA targeting FLCN (n = 2 donors) for 6 days ex vivo, followed by quantitative real-time polymerase chain reaction (qRT-PCR), and quantitative immunohistomorphometry (qIHM). Results Successful FLCN knockdown was confirmed at both the mRNA (34% reduction compared with nontargeting control levels measured by qRT-PCR) and protein level (12% reduction in FLCN expression measured by qIHM). In FLCN-silenced HFs (n = 14, two donors), our preliminary Results demonstrated an increase in p-S6 expression, a direct downstream kinase of mechanistic target of rapamycin complex (mTORC)1 signalling. This was spatially restricted to the hair bulb and proximal outer root sheath keratinocytes, and was significantly greater than quantified in nontargeting control HFs (P &amp;lt; 0.05). Conclusions FLCN silencing in ex vivo cultured, healthy human HFs and scalp skin provides a novel, instructive and accessible preclinical research model. We aim to delineate whether FLCN interacts with the key endogenous inhibitor of mTORC1 activity, TSC2, in future work, to gain insight into the role of FLCN in the pathobiology of BHD and the maintenance of healthy human HFs.

Abstract 6265: FLCN variants and their role in parathyroid cancer and atypical parathyroid tumors

Abstract Parathyroid carcinoma (PC) is rare, poses challenges in definitive diagnosis and treatment, and carries a high rate of recurrence and mortality. Atypical parathyroid tumors (APT) have histopathologic features of malignancy but lack unequivocal evidence of invasion and are of uncertain malignant potential. Analysis of genetic alterations that may play a role in PC development, particularly those that might serve as markers of malignant potential, is important for further understanding this disease. FLCN is a gene found on chromosome 17 that encodes folliculin, a ubiquitously expressed protein with roles in multiple cellular processes such as apoptosis and cell signaling. Inactivating FLCN mutations cause Birt-Hogg-Dubé syndrome (BHD), an autosomal dominant condition characterized by benign fibrofolliculomas, pulmonary cysts and spontaneous pneumothorax, and increased risk of renal cancer. Benign parathyroid tumors had previously been reported in a few BHD patients and recently one study has reported a link between FLCN mutations and parathyroid carcinoma. Germline frameshift mutations in FLCN, accompanied by somatic loss of the normal allele, were reported in two unrelated PC patients, both with clinical features suggestive of BHD, but no established diagnosis of BHD. An identical somatic frameshift FLCN mutation was reported in one PC and one APT. Interestingly, the authors noted low coverage of FLCN on whole exome sequencing, resulting in the failure to detect variants identified by Sanger sequencing, thus raising the possibility that prior studies may have missed FLCN variants. To better understand the frequency of germline or somatic FLCN mutations in PC and APT, we performed Sanger sequence analysis of the entire coding region of the FLCN gene on available tumor DNA from 11 PCs and 15 APTs. We identified no inactivating FLCN mutations in any of the PC or APT samples examined. A germline missense variant, resulting in a p.Gly325Val change, predicted to be benign/tolerated by in silico analyses, was seen in one PC and a synonymous variant (c.1233G&amp;gt;A) was seen in one APT. The absence of pathogenic mutations in our series parathyroid carcinoma and atypical parathyroid tumors suggests that FLCN mutations are rare in these parathyroid tumors. Nevertheless, germline FLCN testing and/or additional screening for BHD-related lesions in parathyroid carcinoma patients merits further consideration and study. Citation Format: Callie Burke, Justin Bellizzi, Jessica Costa-Guda, Andrew Arnold. FLCN variants and their role in parathyroid cancer and atypical parathyroid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6265.

Folliculin gene-negative Birt-Hogg-Dube syndrome: a case report

Introduction and importance: Birt-Hogg-Dube (BHD) is a rare genetic disorder that results from a mutation in the folliculin (FLCN) gene. Manifestations include pulmonary cysts, fibrofolliculomas, renal tumors, and pneumothoraces. Genetic testing can be used to confirm the diagnosis when suspected. BHD syndrome is diagnosed in patients with negative FLCN gene results using diagnostic criteria. Case presentation: A male in his 20s presented with recurrent pneumothoraces. A physical examination revealed bumps on his face and upper body. A chest computed tomography scan revealed cystic lesions. Blood tests, ESR, and CRP levels were unremarkable. Punch skin biopsy revealed fibrofolliculomas. Genetic testing for the FLCN mutation returned negative. His history, physical exam, imaging, and histopathology suggested BHD syndrome despite having a negative family history and genetic analysis. Eventually, the patient was diagnosed with FLCN gene-negative BHD syndrome. Clinical discussion: More than a hundred families have been identified to have BHD worldwide. There are a few cases in the literature describing patients phenotypically presenting with BHD despite having a negative genetic analysis. One study in Japan found 16 out of 157 individuals having a clinical presentation of BHD with no mutations. Also, decreased expression of the FLCN mRNA may lead to BHD. Conclusion: BHD syndrome can present with a negative FLCN gene mutation; however, patients must meet the known diagnostic criteria such as criteria made by Menko et al., Gupta et al., and Schmidt et al. in order to have a diagnosis of BHD syndrome. Also, a qualitative decrease of FLCN with the absence of mutations may also lead to BHD.

Primary sarcoma of prostate: A genomic landscape study.

181 Background: Primary sarcoma of prostate is exceedingly rare and not well-studied. We sought to describe the genomic landscape of this rare entity and identify potential therapy targets. Methods: From 19,057 cases of prostate cancers, only 11 (&lt;.01%) cases of primary sarcomas were identified and underwent comprehensive genomic profiling (CGP) using FDA-approved hybrid capture-based system to assess all classes of genomic alterations (GA). Genomic-based ancestry, genomic signature, gLOH, MSI and TMB status were determined by CGP. Germline status was predicted using a Somatic-Germline-Zygosity algorithm. PD-L1 expression was determined by IHC (Dako 22C3 TPC scoring). Results: The routine histology and IHC stains from all 11 cases were reviewed centrally. There were 9 stromal sarcomas, and 1 each leiomyosarcoma and rhabdomyosarcoma. All patients (median age 57) were clinically advanced stage at the time of CGP. The primary tumor site was used in 6 patients and metastatic sites (3 bone, 1 ureter and 1 lung metastasis) in 5 patients. The mean number of GA per case was 2.3 (1 to 4 GA/sample). The most frequent GA were in TP53 (36.4%), RB1 (27.3%), ATRX (18.2%). Potentially targetable GA were rare and included MTOR pathway inhibitors for GA in TSC2 and PTEN (1 case each) and PIK3CA inhibitors (GA in PIK3CA in 1 case). There were 3 cases with non “targetable” gene rearrangements including a STAT6- NAB2 fusion in a stromal sarcoma (possible solitary fibrous tumor of prostate), a BCOR- MAML3 fusion and a TMPRSS2- ERG fusion in a stromal sarcoma with an adjacent focus of Gleason 6 prostate adenocarcinoma. 1 case featured a predicted germline mutation of the FLCN gene. All cases were microsatellite stable. TMB ranged from 0 to 9.8 mutations/Mb with median of 3.4 mutations/Mb with no cases at ≥10 mutations/Mb. gLOH scores were low, ranging from 0% to 10.9% (median 2.6%). Genomic ancestry was European in 7 patients and Admixed American in 4 others. There were no specific genomic signatures identified. PD-L1 was tested in 4 cases (all negative). Conclusions: Prostate sarcoma is an exceedingly rare primary cancer of the prostate with limited opportunities for targeted therapy or immunotherapy strategies. These tumors do not appear to be driven by “targetable” gene fusions and individual “targetable” mutations are uncommon. [Table: see text]

A pathogenic variant in the FLCN gene presenting with pure dementia: is autophagy at the intersection between neurodegeneration and cancer?

Folliculin, encoded by FLCN gene, plays a role in the mTORC1 autophagy cascade and its alterations are responsible for the Birt-Hogg-Dubé (BHD) syndrome, characterized by follicle hamartomas, kidney tumors and pneumothorax. We report a 74-years-old woman diagnosed with dementia and carrying a FLCN alteration in absence of any sign of BHD. She also carried an alteration of MAT1A gene, which is also implicated in the regulation of mTORC1. The MAT1A variant could have prevented the development of a FLCN-related oncological phenotype. Conversely, our patient presented with dementia that, to date, has yet to be documented in BHD. Folliculin belongs to the DENN family proteins, which includes C9orf72 whose alteration has been associated to neurodegeneration. The folliculin perturbation could affect the C9orf72 activity and our patient could represent the first human model of a relationship between FLCN and C9orf72 across the path of autophagy.

IMPACT OF MITOCHONDRIAL MALFUNCTION IN AGING IS MEDIATED BY IMPAIRED LYSOSOMES AND ENDOPLASMIC RETICULUM

Abstract The hallmarks of aging are well established, and include mitochondrial malfunction, deregulated nutrient sensing, loss of proteostasis, and senescence, among others. While these hallmarks are all part of the aging process, they have typically been studied independently. We have found that mitochondrial malfunction can affect lysosomal activity, impacting nutrient sensing, and our that the crosstalk between mitochondria and other organelles such as endoplasmic reticulum and lysosomes affects cellular senescence, proteostasis and intercellular communication. Chronic mitochondrial malfunction causes perturbations in the lysosomal membrane which affect the function of this organelle as well as the recruitment of folliculin (FLCN) to the lysosomes. FLCN regulates the balance between anabolism (stimulating mTORC1) and catabolism (repressing AMPK). Increased recruitment of FLCN to the lysosomal membrane in cells subjected to chronic mitochondrial malfunction results in hyperactive mTORC1 and inhibition of AMPK signaling, thus aberrantly promoting anabolism under conditions that are not optimal. Furthermore, peroxisomal β-oxidation increases, and expression of proteasome subunits decreases, with consequent perturbation of proteostasis. Overall, the impact of chronic mitochondrial malfunction over lysosomes triggers multiple perturbations in organelles and organelle crosstalk that culminate in aberrant nutrient sensing, metabolic rewiring, proteostasis impairment, senescence and release of sterile inflammation-related proteins to the extracellular medium that denote alterations in intercellular communication. We will build on these findings to explore an overall picture of organelle homeostasis in aging and in age-related diseases.

SAT562 Metastatic Oncocytic (Formerly Hürthle Cell) Thyroid Carcinoma in a Patient With Birt-Hogg-Dubé Syndrome

Abstract Disclosure: S. Vaid: None. R. Klein: None. P. Veeraraghavan: None. D.M. Blakaj: None. A. Agrawal: None. J. Sipos: None. S.I. Sherman: None. J. Klubo-Gwiezdzinska: None. S. Gubbi: None. Introduction: Birt-Hogg-Dubé syndrome (BHD) is a rare, autosomal dominant disorder due to a germline loss-of-function mutation in the folliculin (FLCN) gene. Clinical manifestations include pulmonary cysts, renal cell carcinoma, and skin tumors, while tumors of other sites such as thyroid are uncommon. Here, we report an extremely rare case of oncocytic thyroid carcinoma (OTC) in a patient with BHD. Clinical case: A 55-year-old male with BHD noted a lump in his neck which was identified as a 3 cm right thyroid nodule on sonogram. Medical history only included BHD, which was diagnosed based on the presence of pulmonary cysts and two family members with BHD. No family members had thyroid tumors, and the patient denied any history of radiation exposure. Fine needle aspiration biopsy was indeterminate (Bethesda III). A total thyroidectomy and central lymph node (LN) dissection was performed as LN metastases were identified on intraoperative frozen section. Histopathology revealed 3 foci of OTC, largest being 3.8 cm, with extrathyroidal extension into fibroadipose tissue, 3/31 LN metastases with the largest deposit of 0.5 cm without extranodal extension. A 156.6 mCi dose of I-131 radioiodine (RAI) was administered. No uptake was noted on the post-therapy scan. Four months later, new right lateral cervical lymphadenopathy was noted on computed tomogram (CT). A right lateral selective neck dissection was performed, which identified 3/28 metastatic LNs without extranodal extension. Next generation gene sequencing testing of the metastatic tumor revealed the pathogenic FLCN (H429fs*27) variant, along with TP53 (R248Q), and DAXX (L666fs*29) pathogenic variants. Over the next 20 months, serum thyroglobulin increased from 1.8 ng/ml to 121 ng/mL (normal: 1.6 - 59.9 ng/mL). Several sub-centimeter lung nodules and new right cervical lymphadenopathy were noted on CT, and these lesions demonstrated increased uptake on fluorodeoxyglucose positron emission tomography (PET/CT) and on Ga-68 DOTATATE PET/CT scans. Due to close proximity to the right internal jugular vein, the cervical lymphadenopathy was deemed to be inoperable. Stereotactic radiation was administered to the neck, which resulted in substantial shrinkage of the neck metastases. The patient continues to be on active surveillance, with tyrosine kinase inhibitors or peptide receptor radionuclide therapy being potential future systemic therapy options in case of disease progression. Conclusion: Thyroid tumors have been occasionally reported in BHD. While most of them are papillary or follicular tumors, only one case of OTC in BHD has been previously reported in the literature [1]. This report underscores the importance of screening for thyroid neoplasms in patients with BHD. Reference: 1. Panagiotidis et al. World J Nucl Med. 2018;17(2):123-125 Presentation Date: Saturday, June 17, 2023

THU514 Atypical Presentation Of Birt-Hogg-Dubé Syndrome With Poorly Differentiated Follicular Thyroid Cancer And Paraganglioma

Abstract Disclosure: K. Lertdetkajorn: None. J. Haw: None. J.E. Paysour: None. Background: Birt-Hogg-Dubé syndrome (BHDS) is a rare genetic disorder typically presenting with skin hamartomas, renal tumors, and lung cysts. BHD is caused by germline mutations of the folliculin (FLCN) gene. We present the case of a patient with follicular thyroid cancer and paraganglioma diagnosed with BHDS. Case: A 64-year-old female was noted to have progressive enlargement of a neck mass over six months following admission for a hypertensive emergency. CT neck demonstrated a heterogeneous mass centered within the left thyroid lobe measuring 10.4 x 8.6 x 7.6 cm with internal calcifications. TSH was normal. FNA of this mass was suspicious for follicular neoplasm, and she underwent a total thyroidectomy. The pathology reported poorly differentiated adenocarcinoma of the thyroid gland, follicular variant, pT3aN0M0 with positive margins, and lymph-vascular space invasion (LVI). FDG-PET/CT scan showed postsurgical changes of a total thyroidectomy with ill-defined FDG uptake along the left thyroid bed, 3 x 2.8 cm portacaval lymph node (SUV of 9.6) and focal soft tissue FDG avid rectal abnormality. MRI abdomen demonstrated a 4.0 x 4.1 x 3.2 cm soft tissue mass characterized by arterial hyperenhancement and washout in the portacaval region broadly interfacing with the IVC, main portal vein, and left renal vein. EGD was unremarkable, but an EUS demonstrated 3.7 x 3.5 hypoechoic, well-circumscribed, mild-vascular hypoechoic portocaval mass. FNA of this mass was consistent with paraganglioma. Laboratory results supported the diagnosis of paraganglioma with urine metanephrine 9661 mcg/24 h (224 - 832 mcg/24 h) and urine normetanephrine 9457 mcg/24 h (122 - 676 mcg/24 h). The patient was referred for genetic testing to investigate whether the co-existence of follicular thyroid cancer and paraganglioma was secondary to a genetic disorder. The germline genetic testing revealed the pathogenic variant, c.1436dup (p.Thr481Hisfs*5), identified in the FLCN gene with no detections of VHL or SDH complex variants, confirming the diagnosis of BHDS. The patient later underwent a colonoscopy and was found to have stage I colon cancer. Some early reports have shown an association between BHDS and colon tumors. The patient decided not to have any surgery at this time. She continues to follow up in the clinic and takes levothyroxine for suppressive goals. Octreotide LAR, along with blood pressure medications including phenoxybenzamine, was started to treat her paraganglioma. Conclusion: Patients with BHDS may present with atypical clinical manifestations. Genetic testing will aid in diagnosing a germline mutation in the FLCN gene. The association between thyroid cancer and BHDS has been reported previously; however, paraganglioma as a spectrum of BHDS has not been published. Further reported cases and research may provide additional data to investigate the relationship between BHDS and paraganglioma. Presentation: Thursday, June 15, 2023

Systemic Treatment for Advanced and Metastatic Non-Clear Cell Renal Cell Carcinoma: Examining Modern Therapeutic Strategies for a Notoriously Challenging Malignancy.

Non-clear cell renal cell carcinoma (nccRCC) is a heterogeneous group of malignancies that represents 25% of renal cell carcinoma (RCC) cases. Treatment for non-clear cell histologies is mostly based on evidence from small phase II clinical trials or extrapolated from successful therapies in clear cell RCC because of the low incidence of non-clear cell pathology. Advances in genomic profiling have improved clinicians' understanding of molecular targets for nccRCC, such as altered mesenchymal epithelial transition (MET) gene status and fumarate hydratase (FH) gene inactivation, but patient outcomes remain poor and optimal management of this disease remains unclear. This review assesses outcomes by histologic subtype from 27 prospective and 13 ongoing clinical trials to identify therapeutic strategies for advanced or metastatic nccRCC. Vascular endothelial growth factor tyrosine kinase inhibitors (TKI), such as sunitinib, and mammalian target of rapamycin (mTOR) inhibitors, such as everolimus, have demonstrated efficacy and remain viable treatment options, with a preference for sunitinib. However, everolimus is preferred in patients with chromophobe RCC because folliculin (FLCN) gene mutations upregulate the mTOR pathway. Novel TKIs, such as cabozantinib, show improved outcomes in patients with papillary RCC because of targeted MET inhibition. Platinum-based chemotherapy continues to be the recommended treatment strategy for collecting duct and medullary RCC. Clinically meaningful antitumor activity has been observed across all non-clear cell histologies for immune checkpoint inhibitors, such as nivolumab, pembrolizumab, and ipilimumab. Ongoing trials are evaluating novel tyrosine kinase inhibitor and immunotherapy combination regimens, with an emphasis on the promising MET-inhibitor cabozantinib and pembrolizumab plus lenvatinib.

A retrospective cohort study investigating the etiology of primary spontaneous pneumothorax in children: Radiological and genetic analysis

Background/Aim: Spontaneous pneumothorax is a serious health concern due to its life-threatening nature. It occurs when air sacs in the lungs rupture, causing air to accumulate in the chest cavity and making normal breathing difficult. Primary spontaneous pneumothorax (PSP) refers to the accumulation of air in the pleural space without any traumatic or iatrogenic cause. The objectives of our study are to identify the predisposing factors in PSP patients, determine which patients should undergo genetic analysis, and present the results of a new treatment algorithm. Methods: This study is a retrospective cohort analysis of children diagnosed with PSP and admitted to the emergency department or pediatric surgery clinic. The study evaluates demographic data, radiological findings, and molecular genetic analyses of these patients. Treatment planning was conducted using thoracic computed tomography (CT) or high-resolution computed tomography (HRCT) after the acute phase, and eligible patients were selected for genetic analysis based on syndromes commonly associated with PSP. Results: The study included 14 patients, 10 boys and four girls, with an average age of 16.14 (0.95) years. PSP was detected on the right side in nine male patients and on the left side in one male patient, while in girls, it was detected on the right side in two patients and on the left side in two patients. Radiological findings included air cysts, fibrotic changes, and pleural thickening. Folliculin (FLCN) mutation was detected in two patients after genetic analysis. Conclusion: In the stratified treatment protocol, radiological findings were used as a guide, and the detection of possible syndromic mutations by genetic analysis was deemed important for future management.

A splicing mutation of the FLCN gene is associated with Birt-Hogg-Dubé syndrome characterized by familial and recurrent spontaneous pneumothorax: A case report.

Birt-Hogg-Dubé (BHD) syndrome is a rare autosomal recessive genetic disorder caused mainly by mutations in the tumor suppressor FLCN gene. Tumors caused by FLCN mutations are frequently benign and develop in skin, lungs, kidney, and other organs, leading to a variety of phenotypes that make early diagnoses of BHD challenging. A 51-year-old female was admitted to Shanghai Seventh People Hospital due to chest congestion and dyspnea that had persisted for 3 years and aggravated for 1 month. She had been diagnosed with pneumothorax prior to this submission, but the etiology was unknown. Chest computed tomography (CT) revealed multiple pulmonary cysts and pneumothorax, and her family members shared similar manifestation. Whole-exome sequencing analysis indicated a heterozygous FLCN splicing mutation (c.1432 + 1G > A; rs755959303), which was a pathogenic variant indicated in ClinVar. Based on FLCN mutation and the family history of pulmonary cysts and pneumothorax, BHD syndrome was finally diagnosed, which had been delayed for 3 years since her first pneumothorax. Pulmonary bullectomy and pleurodesis were finally conducted due to the poor effects of thoracic close drainage. Her pneumothorax was resolved, and no recurrence was found in 2 years. Our study highlights the importance of genetic analysis in diagnosis and clinical management of BHD syndrome.

Comparative analyses define differences between BHD-associated renal tumour and sporadic chromophobe renal cell carcinoma.

Birt-Hogg-Dubé (BHD) syndrome, caused by germline alteration of folliculin (FLCN) gene, develops hybrid oncocytic/chromophobe tumour (HOCT) and chromophobe renal cell carcinoma (ChRCC), whereas sporadic ChRCC does not harbor FLCN alteration. To date, molecular characteristics of these similar histological types of tumours have been incompletely elucidated. To elucidate renal tumourigenesis of BHD-associated renal tumours and sporadic renal tumours, we conducted whole genome sequencing (WGS) and RNA-sequencing (RNA-seq) of sixteen BHD-associated renal tumours from nine unrelated BHD patients, twenty-one sporadic ChRCCs and seven sporadic oncocytomas. We then compared somatic mutation profiles with FLCN variants and RNA expression profiles between BHD-associated renal tumours and sporadic renal tumours. RNA-seq analysis revealed that BHD-associated renal tumours and sporadic renal tumours have totally different expression profiles. Sporadic ChRCCs were clustered into two distinct clusters characterized by L1CAM and FOXI1 expressions, molecular markers for renal tubule subclasses. Increased mitochondrial DNA (mtDNA) copy number with fewer variants was observed in BHD-associated renal tumours compared to sporadic ChRCCs. Cell-of-origin analysis using WGS data demonstrated that BHD-associated renal tumours and sporadic ChRCCs may arise from different cells of origin and second hit FLCN alterations may occur in early third decade of life in BHD patients. These data further our understanding of renal tumourigenesis of these two different types of renal tumours with similar histology. This study was supported by JSPS KAKENHI Grants, RIKEN internal grant, and the Intramural Research Program of the National Institutes of Health (NIH), National Cancer Institute (NCI), Center for Cancer Research.

Exons 1–3 deletion in FLCN is associated with increased risk of pneumothorax in Chinese patients with Birt-Hogg-Dubé syndrome

BackgroundThe pathogenic variants responsible for Birt-Hogg-Dubé syndrome (BHDS) in folliculin (FLCN) gene mostly consist of point mutations. Although large intragenic deletions/duplications have been reported in several case reports, the relationship between large intragenic deletions/duplications and phenotype in BHDS remains unclear.MethodsWe retrospectively identified and reviewed patients with a large intragenic deletion spanning exons 1–3 and analyzed their phenotypic features to compare with those of point mutation carriers in our hospital from January 1, 2017 to August 31, 2022.ResultsTwenty unique point mutations (including 4 novel mutations) were detected in 62 patients from 45 families (90%). Exons 1–3 deletion were identified in 8 patients from 5 families (10%) that resided in the same region, Feidong County of Anhui Province, China. Breakpoint analysis indicated that all the deletion breakpoints were flanked by Alu repeats. The prevalence of exons 1–3 deletion carriers in Feidong County was 8.1-times higher than that for BHDS in Anhui Province, suggesting a clustered phenomenon of exons 1–3 deletion. Significantly increased risk of pneumothorax was observed in those with exons 1–3 deletion compared with point mutations (91% vs. 58%, p value 0.047). The risk of renal cancer may be higher in those with exons 1–3 deletion than for those with point mutations (18% vs. 4%, p > 0.05).ConclusionsLarge intragenic deletion of exons 1–3 in FLCN was identified as a local aggregation phenomenon in Feidong County, China, and was associated with a significantly higher risk of pneumothorax compared to those with point mutations.