Hereditary leiomyomatosis and renal cell carcinoma syndrome associated uterine smooth muscle tumors: Bridging morphology and clinical screening

Fumarate Hydratase-Deficient Leiomyoma of the Uterine Corpus: Comparative Morphologic Analysis of Protein-Deficient Tumors With and Without Pathogenic Germline Fumarate Hydratase Gene Mutations

Deficiency of fumarate hydratase (FH) protein expression in uterine corpus leiomyomas may be attributable to either germline or somatic mutations of the FH gene, the former being definitional for the hereditary leiomyomatosis and renal cell cancer syndrome. The authors assess whether, using previously reported FH-associated morphologic features, FH protein-deficient uterine corpus leiomyomas associated with a pathogenic germline mutations of the FH gene (group 1) are distinguishable from FH protein-deficient uterine corpus leiomyomas without such mutations (and whose FH protein loss is presumed to be attributable to somatic/epigenetic inactivation or other unknown phenomena: group 2). Groups 1 and 2 were compared regarding a variety of clinicopathologic features, including 7 core "FH-associated" tumoral morphologic features: staghorn vasculature; alveolar-type edema; bizarre nuclei; chain-like tumor nuclei; hyaline cytoplasmic globules; prominent nucleoli, intranuclear inclusions, and perinucleolar halos; and prominent eosinophilic/fibrillary cytoplasm. Among 2418 patients diagnosed with uterine corpus leiomyoma during the study period, FH-associated morphologic features were reported in 1.5% (37 patients), and FH immunohistochemistry was performed in 29 (1.19%). Fourteen (48.27%) of the 29 patients showed FH protein deficiency by immunohistochemistry. Twelve patients underwent germline testing, of which 8 (66.7%) were classified as group 1 and 4 (33.3%) as group 2. FH protein-deficient tumors were larger (10.44 vs 4.08 cm, P  =  0.01) and associated with younger patients (42.05 vs 47.97, P  =  0.004) than 370 randomly selected uterine leiomyoma controls. Groups 1 and 2 showed no significant differences in patient age and tumor size. In group 1 tumors, the FH-associated morphologic features were generally present diffusely; all group 1 tumors displayed ≥5 FH-associated features, whereas all group 2 tumors displayed <5 FH-associated features (means 6.5  ±  0.53 vs 3.5  ±  1.00, P < 0.001). Notably, eosinophilic/fibrillary cytoplasm and alveolar-type edema were each significantly more prevalent in group 1 tumors than group 2 tumors (P  =  0.018 for both). No single morphologic feature was found to be completely sensitive and specific in making the distinction between group 1 and 2 tumors. Our findings suggest that groups 1 and 2 are unlikely to be morphologically distinguishable by individual morphologic features. Whether there is a combination of features that can reliably make this distinction is unclear and will require additional studies with larger cohorts.

FH deficient uterine leiomyomas-a case series

Introduction

Fumarate hydratase (FH) deficient uterine leiomyomas account for only 0.4 % of all uterine leiomyomas. They are characterized by some distinct histological features and may be associated with Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome.

Methods

Herein we present a series of five cases of FH deficient uterine leiomyomas in patients with a mean age of 30 years. All five patients underwent myomectomy. Three of these cases had an outside histopathologic diagnosis ranging from Smooth muscle tumor of uncertain malignant potential (STUMP) to Leiomyosarcoma while two cases were operated at our centre. All five cases were reported as suggestive of FH deficient leiomyomas and were advised germline testing along with genetic counselling.

Results

Immunohistochemically four of the cases showed moderate to strong positivity for 2-SC with a complete loss or reduced expression of FH while one case showed absence of 2-SC staining.

Discussion

Mutations in FH lead to reduced enzyme activity and accumulation of fumarate leading to a complete loss or aberrant reduced expression seen on immunohistochemistry, which confirms the diagnosis. It is important to differentiate it from a leiomyosarcoma or other malignant spindle cell tumors as these tumors follow a benign course. Their association with HLRCC also needs to be established for a suitable follow up since HLRCC-associated RCCs are often aggressive.

Conclusion

Management of such leiomyomas is myomectomy or hysterectomy with advice of genetic testing to rule out HLRCC. Histomorphology and immunohistochemistry are imperative for a correct and timely diagnosis.

The use of Clinicopathological, immunohistochemistry and molecular detection in the diagnosis of fumarate hydratase-deficient uterine leiomyomas

BACKGROUND

Fumarate hydratase-deficient uterine leiomyomas (FH-dUL) are rare, accounting for only 0.4-1.6% of uterine leiomyomas. FH germline mutation gene is associated with hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC).

METHODS

In this study, we aim to investigate Clinicopathological features and FH mutation in FH-dUL. We performed a retrospective analysis of 300 cases of uterine leiomyoma, diagnosed from January 2017 to December 2021, within the archives of the Department of Pathology at Peking University People's Hospital. In our review of the immunohistochemical(IHC) staining was performed on 300 uSMTs to detect FH deficiency.

RESULTS

We identified 21cases (21/300,7%) of FH-dUL. Nineteen cases (6.33%) displayed negative FH. Twenty-one cases (7%) displayed 2SC diffuse plasma and nuclear staining. The most common FH-d morphological features included staghorn vasculature ( 100%,21/21), alveolar-pattern oedema (71.43%, 15/21), scattered bizarre nuclei (23.81%, 5/21), eosinophilic cytoplasmic (rhabdoid) inclusions (47.62%, 10/21), significant eosinophilic nucleolus with peri-nucleolus hollowing (23.81%, 5/21), ovoid nuclei sometimes arranged in chains (9.52%, 2/21). DNA sequencing for the 21 cases was performed using Next Generation Sequencing (NGS). 6 cases were detected significant variations for the FH gene, 11 cases were detected FH gene mutation forvariants of uncertain significance (VUS), and 2 cases were detected a TP53 gene mutation. No related mutations were detected in the other two cases.

CONCLUSIONS

FH-dUL is rare. The combination of predictive Clinicopathological evaluation,FH and 2SC IHC test, and molecular test were helpful for the screening of FH-dUL from uSMTs,or even the screening of HLRCC.

The Role of Morphology in Predicting Fumarate Hydratase-deficient Uterine Leiomyomas in Young Women

Hereditary leiomyomatosis and renal cell carcinoma is caused by germline mutations in the fumarate hydratase (FH) gene and is associated with an increased incidence of leiomyomas and a potentially aggressive variant of renal cell carcinoma. Pathologic evaluation of uterine leiomyoma can provide an opportunity for early recognition of the syndrome. We reviewed all archived slides of the cases to identify the characteristic morphologic features described for FH-deficient leiomyomas. We performed immunohistochemistry on whole sections of patients with uterine leiomyoma to evaluate for both FH and 2-succinocysteine (2SC) expression. Of the 106 cases, 19 showed the characteristic eosinophilic nucleoli with perinuclear halos, and 24 revealed a characteristic eosinophilic cytoplasmic inclusion consisting of pink globules present within the cytoplasm. Both of these morphologic findings were present together in 15 cases, and hemangiopericytomatous vessels were detected in 23 cases. The loss of FH protein expression was detected in 14 out of 106 cases (13%), and 13 out of 106 cases (12%) were positive for 2SC. We detected 10 cases with both 2SC-positive and FH expression loss. The presence of eosinophilic nucleoli with perinuclear halos and eosinophilic cytoplasmic inclusion was associated with both loss of FH protein expression and 2SC positivity ( P < 0.001). These findings underscore the importance of hematoxylin and eosin-based predictive morphology in FH-deficient uterine leiomyomas. Therefore, morphologic assessment of uterine leiomyomas for features of FH deficiency can serve as a screening tool for hereditary leiomyomatosis and renal cell carcinoma syndrome, allowing patients to be divided according to their hereditary risk assessment.

Fumarate Hydratase and S-(2-Succinyl)-Cysteine Immunohistochemistry Shows Evidence of Fumarate Hydratase Deficiency in 2% of Uterine Leiomyosarcomas: A Cohort Study of 348 Tumors

Approximately 1% to 1.5% of uterine leiomyomas are fumarate hydratase (FH)-deficient (FHd). A subset of these are associated with germline FH mutations. However, the prevalence and clinicopathologic characteristics of FHd uterine leiomyosarcoma (uLMS) remain unknown. Clinicopathologic data were collected for 348 uLMS. Morphologic features associated with FH deficiency (staghorn-type vessels, alveolar-pattern edema, macronucleoli with perinucleolar clearing, eosinophilic cytoplasmic inclusions, and chain-like nuclear arrangement) were documented. All 348 tumors were studied by FH immunohistochemistry. Eighty-nine were also studied by S-(2-succinyl)-cysteine (2SC) immunohistochemistry. Seven (2%) FHd uLMS were identified. Five showed uniformly negative FH and diffusely positive 2SC immunostaining; 1 showed variably negative to weak to strong FH and diffusely positive 2SC immunostaining; and 1 showed retained FH staining alongside positive 2SC confined to a morphologically distinct subclone. Three of 7 patients had extrauterine disease at presentation, and 3 of 6 had persistent disease or died from disease. Macronucleoli with perinucleolar clearing were significantly more common in FHd uLMS (7/7) than in uLMS with retained FH (182/341; P =0.017). Disease-specific survival, disease-free survival, and other morphologic features of FH deficiency did not differ significantly between FHd and FH-retained tumors. Our data emphasize that immunohistochemical FH deficiency does not preclude malignancy in uterine smooth muscle tumors. However, the biological significance and molecular basis of FH deficiency in uLMS, including any relationship to germline FH mutation, remain unknown, and a larger multi-institutional effort is necessary to gather sufficient FHd uLMS for more robustly powered clinicopathologic and for molecular characterization.

Fumarate hydratase gene germline variants and mosaicism associated with pheochromocytoma and paraganglioma

Fumarate hydratase (FH) catalyzes the conversion of fumaric acid to L-malic acid. Heterozygous variants of the human fumarate hydratase gene (FH) predispose to hereditary leiomyomatosis and renal cell cancer and, rarely, pheochromocytoma/paraganglioma (PPGL). No mosaic variant in FH has been reported yet. Using next-generation sequencing, five individuals with FH variants were found in 319 PPGL patients. Immunohistochemistry staining and loss of heterozygosity analysis in tumor tissues were performed to determine the pathogenicity of the variants. Deep targeted sequencing was performed on the peripheral blood DNA of a pheochromocytoma (PCC) patient with uterine leiomyomas. Finally, two of the five variants were found to be pathogenic. A germline variant (c.817G>A, p.Ala273Thr) was found in a patient with a PPGL family history. A mosaic variant (c.206G>A, p.Gly69Asp) with an allelic ratio of 5% in blood DNA was confirmed in the PCC patient with uterine leiomyomas. No metastatic PPGL was observed in the two PPGL patients with FH pathogenic variants. In summary, we report mosaicism in FH and the first PPGL pedigree with an FH pathogenic germline variant. Both germline variants and mosaicism should be taken into account during genetic testing.

Phenotypic and Genetic Complexity in Pediatric Movement Disorders

The complex and evolving nature of clinical phenotypes have made genetically diagnosing pediatric patients with movement disorders difficult. Here, we describe this diverse complexity in the clinical and genetic features of a pediatric cohort examined by whole-exome sequencing (WES) and demonstrate the clinical benefit of WES as a diagnostic tool in a pediatric cohort. We evaluated 75 patients with diverse single or combined movement phenomenologies using WES. WES identified 42 variants in 37 genes (56.0%). The detection rate was highest in patients with dystonia (11/13, 84.6%), followed by ataxia (21/38, 55.3%), myoclonus (3/6, 50.0%), unspecified dyskinesia (1/4, 25.0%), tremor (1/1, 100%), respectively. Most genetically diagnosed patients (90.5%) were affected by other neurologic or systemic manifestations; congenital hypotonia (66.7%), and epilepsy (42.9%) were the most common phenotypes. The genetic diagnosis changed the clinical management for five patients (6.7%), including treatments targeting molecular abnormalities, and other systemic surveillance such as cancer screening. Early application of WES yields a high diagnostic rate in pediatric movement disorders, which can overcome the limitations of the traditional phenotype-driven strategies due to the diverse phenotypic and genetic complexity. Additionally, this early genetic diagnosis expands the patient’s clinical spectrum and provides an opportunity for tailored treatment.

Clinicopathological and molecular characteristics of fumarate-hydratase-deficient uterine smooth muscle tumors: A single-center study of 52 cases

AIMS

The fumarate hydratase (FH) gene germline mutations cause hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC), predisposing carriers to uterine and cutaneous leiomyomas and renal cell carcinoma (RCC). In this study, we aim to investigate morphology and the correlation between FH mutation in FH-deficient (FH-d) uterine smooth muscle tumors (uSMTs).

METHODS AND RESULTS

We conducted immunohistochemical staining in 161 cases of uSMTs to detect FH deficiency. We identified 52 (52/161, 32%) cases of FH-d, including 34 leiomyomas with bizarre nuclei, 10 uSMTs of uncertain malignant potential (STUMPs), 4 cellular leiomyomas, 3 usual type leiomyomas, and 1 leiomyosarcoma. Patients with FH-d were aged 24-67 years (median, 40 years). The most common FH-d morphological features included staghorn-shaped blood vessels (87%), bizarre nuclei (81%), alveolar pattern edema (65%), macronucleoli surrounded by a halo (65%), cytoplasmic eosinophilic globules (56%), and chain-like distribution of smooth muscle cells (52%). A targeted next generation sequence was performed in 11 of 52 FH-d tumors. Five (5/11, 45%) cases were found with FH germline mutations, including four leiomyomas with bizarre nuclei and one STUMP. The median age of patients with germline FH mutation was 30 years. The germline mutations including three pathogenic, one likely pathogenic, and one rare uncertain clinical significance variants.

CONCLUSIONS

Our results revealed that FH-d uSMTs usually exhibit the distinct morphology features and high frequency of FH germline mutations. The combination of predictive morphology evaluation, FH immunotype and molecular testing is helpful for the screening of HLRCC in uSMTs.

Key changes to the world health organisation (who) classification of female genital tumours introduced in the 5TH edition (2020)

An updated World Health Organisation (WHO) Classification of Female Genital Tumours was published in Autumn 2020. We discuss the major new additions and changes from the prior 2014 Classification with discussion of the reasons underlying these. A feature of the new Classification is the greater emphasis on key molecular events with integration of morphological and-molecular features. Most of the major changes from the prior Classification pertain to uterine (corpus and cervix) and vulval tumours but changes in all organs are covered.

Fumarate hydratase variant prevalence and manifestations among individuals receiving germline testing

BACKGROUND

Germline variants in fumarate hydratase (FH) are associated with autosomal dominant (AD) hereditary leiomyomatosis and renal cell cancer (HLRCC) and autosomal recessive (AR) fumarase deficiency (FMRD). The prevalence and cancer penetrance across different FH variants remain unclear.

METHODS

A database containing 120,061 records from individuals undergoing cancer germline testing was obtained. FH variants were classified into 3 categories: AD HLRCC variants, AR FMRD variants, and variants of unknown significance (VUSs). Individuals with variants from these categories were compared with those with negative genetic testing.

RESULTS

FH variants were detected in 1.3% of individuals (AD HLRCC, 0.3%; AR FMRD, 0.4%; VUS, 0.6%). The rate of AD HLRCC variants discovered among reportedly asymptomatic individuals without a clear indication for HLRCC testing was 1 in 2668 (0.04%). In comparison with those with negative genetic testing, the renal cell carcinoma (RCC) prevalence was elevated with AD HLRCC variants (17.0% vs 4.5%; P < .01) and VUSs (6.4% vs 4.5%; P = .02) but not with AR FMRD variants.

CONCLUSIONS

The prevalence of HLRCC discovered incidentally on germline testing is similar to recent population carrier estimates, and this suggests that this is a relatively common cancer syndrome. Compared with those with negative genetic testing, those with VUSs had an elevated risk of RCC, whereas those with AR FMRD variants did not.

Uterine leiomyomatosis in adolescents and young adults (AYAs) may represent a narrow phenotypic variant of FH tumour predisposition syndrome

FH Tumour Predisposition Syndrome, also known as Hereditary Leiomyomatosis and renal cell cancer (HLRCC), or Reed Syndrome, is an autosomal dominant condition clinically characterized by multiple cutaneous leiomyomas, multiple early-onset uterine leiomyomas and early-onset renal cell cancer. Here we report a young female with FH Tumour Predisposition Syndrome with no clinical features except early-onset uterine leiomyomas. Whilst there is a significant history of uterine leiomyomas in her family, there is no history of cutaneous leiomyomas or renal cell cancer (RCC). Uterine leiomyomatosis in young adults may represent a narrow phenotypic variant of FH Tumour Predisposition Syndrome. It is important that young women who present with multiple leiomyomata or leiomyomata with atypical features are referred for molecular genetic testing.

[FH-deficient renal cell carcinoma expands the spectrum of renal papillary tumors]

Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a distinct entity, which shows a biallelic inactivation of the FH gene that consequently leads to FH protein expression and function loss, respectively. This alteration leads to an accumulation of the oncometabolite fumarate in the citrate cycle and various disorders of the cell balance and DNA processing. FH-deficient RCC often shows a morphologically overlapping spectrum with papillary renal cell carcinoma (type 2), whereby a typical mixture of growth patterns including tubulo-cystic, cribriform, and/or solid differentiation can be observed. A characteristic but non-specific morphological feature is prominent eosinophilic, virus-inclusion body-like nucleoli with perinucleolar halos. Tumoral immunohistochemical loss of FH expression supports the diagnosis but may be preserved in rare cases. Most FH-deficient RCCs show very aggressive biological behavior and are often metastasized at the time of diagnosis. The initial description encompassed RCC in association with the hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, which also includes cutaneous and uterine leiomyomas. However, current data also show an increasing proportion of sporadic cases, so that a distinction (hereditary vs. sporadic) seems appropriate. So far, few but promising data on effective systemic therapeutic options have been reported. In summary, precise diagnosis is of great importance due to the frequent aggressive biological behavior, potential need to deviate from the therapeutic standard, and the possible indicator of a hereditary disease.

Gene of the month: FH

Fumarate hydratase (FH), encoded by the FH gene, is an enzyme which catalyses the conversion of fumarate to L-malate as part of the tricarboxylic acid cycle. Biallelic germline mutations in FH result in fumaric aciduria, a metabolic disorder resulting in severe neurological and developmental abnormalities. Heterozygous germline mutations in FH result in hereditary leiomyomatosis and renal cell carcinoma, a cancer predisposition syndrome. FH deficiency has multiple oncogenic mechanisms including through promotion of aerobic glycolysis, induction of pseudohypoxia, post-translational protein modification and impairment of DNA damage repair by homologous recombination. FH-deficient neoplasms can present with characteristic morphological features that raise suspicion for FH alterations and also frequently demonstrate loss of FH immunoreactivity and intracellular accumulation of 2-succinocysteine, also detected by immunohistochemistry.

Primary Leiomyoma of the Visceral Pleura: An Unexpected Occurrence

BACKGROUND/AIM

Leiomyoma is a rare benign tumor originating from smooth muscle fibres. In the respiratory tract, these tumors are rare and in the pleura, cases are exceptional, with only a few reported so far. This is the main reason we decided to present this case of primary leiomyoma of the visceral pleura.

CASE REPORT

We present a case of a 51-year-old asymptomatic patient who, during a routine medical examination using standard chest radiography, presented with a 3 by 2 cm homogenous mass in the right superior pulmonary area, tangent to the chest wall (same level with the 3rd rib). Further investigation using computed tomography (CT) in the chest confirmed the presence of a 31/18 mm solid mass in the right upper lobe, in contact with the parietal pleura. Surgery was performed for two reasons: i) removal of the tumoral mass and ii) establishing a histopathological diagnosis. Intraoperatively, a well-defined, homogenous, ivory white non-infiltrating mass was discovered in the right upper lobe on the visceral pleura and in close proximity to the minor fissure. The mass was removed with negative surgical margins and was left with healthy tissue. Histopathological examination and immunohistochemistry came as a surprise, establishing our diagnosis of leiomyoma.

CONCLUSION

Primitive pleural leiomyoma must remain a possibility when considering the differential diagnosis of pleural tumors. The main course of treatment is complete surgical resection. In our case, long-term follow up did not present any local recurrence.