Detailed Morphologic and Immunohistochemical Characterization of Myomectomy and Hysterectomy Specimens From Women With Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome (HLRCC)

Abstract

Hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC), caused by a germline mutation in the fumarate hydratase (FH) gene, predisposes patients to uterine and cutaneous smooth muscle tumors and an aggressive type of renal cell carcinoma. Almost all women with HLRCC develop symptomatic uterine leiomyomas resulting in surgery at young ages, presenting an ideal opportunity for early detection of these patients and the implementation of surveillance measures for renal cell carcinoma. FH-deficient uterine leiomyomas can show characteristic morphologic features (FH-d morphology) that have been previously described. Immunohistochemistry (IHC) for FH can also be helpful in detecting FH deficiency in leiomyomas, which manifests as complete loss of staining for FH. However, the distribution and topography of FH-d morphology and FH loss by IHC in the context of multiple leiomyomas in patients with HLRCC has not been evaluated. The aim of this study is to describe in detail the clinical and pathologic characteristics of uterine leiomyomas from women with HLRCC. Six patients with proven FH germline mutations were included. All available slides were reviewed and FH IHC staining was performed on multiple blocks when possible. Clinical data were extracted from online medical records. All 6 patients presented with symptomatic uterine fibroids and underwent myomectomy (age 24 to 36 y), followed by hysterectomy in 2 patients (age 31 and 40 y). Specimens showed conventional leiomyomas, cellular leiomyomas and leiomyomas with bizarre nuclei. FH-d morphology was present in leiomyomas from all patients and was typically observed as a diffuse finding in the majority of slides across different leiomyoma types. FH-d morphology was absent in some leiomyoma sections from one patient and the morphologic features were focal and subtle in leiomyomas from 2 patients. Both hysterectomy specimens were also notable for showing scattered irregular tongues and nodules of smooth muscle proliferation (leiomyomatosis-like) in the background myometrium. Immunohistochemical staining of multiple slides per patient for FH showed either retained staining in all sections (2/6 cases), loss of staining in all sections (1 case) or variable staining across different leiomyomas (3 cases). In conclusion, patients with HLRCC undergo surgery at young ages for highly symptomatic uterine leiomyomas. FH-d morphology is usually a diffuse and well developed finding across different leiomyomas but may be absent or focal and subtle. FH IHC can show variable results and presence of retained FH staining should not be used to exclude the possibility of HLRCC. Referral for genetic counselling and testing should be considered in a young patient with uterine leiomyomas showing FH-d morphology even if immunohistochemical staining for FH is retained.

Targeted sequencing of FH-deficient uterine leiomyomas reveals biallelic inactivating somatic fumarase variants and allows characterization of missense variants

“…This successful approach allowed us to identify a cluster of missense variants associated with immunohistochemical protein reduction, proving that missense variants contribute to FH deficient ULs. We agree with previous concerns [ 15 , 17 , 18 ] that some pathogenic missense variants in individuals with HLRCC might be missed using only FH IHC as screening method. The proposedly more reliable 2SC IHC is currently not available for routine use.…”

“…Immunohistochemistry (IHC) can be used to confirm the morphological suspicion. Loss of staining for the FH gene product FH is an intuitive direct marker, but recent reports of retained staining in tumors with pathogenic missense variants raised concerns about its validity as marker for FH deficiency [ 15 , 18 ]. In contrast, staining for 2SC (S-(2-succinyl) cysteine), a covalent protein modification that accumulates when the FH in cells is nonfunctional, has excellent statistical performance despite being an indirect marker of enzyme function [ 19 , 23 , 24 ].…”

“…In contrast, staining for 2SC (S-(2-succinyl) cysteine), a covalent protein modification that accumulates when the FH in cells is nonfunctional, has excellent statistical performance despite being an indirect marker of enzyme function [ 19 , 23 , 24 ]. Unfortunately, the 2SC antibody is currently not commercially available which excludes the use in a clinical setting [ 15 , 16 , 18 ]. Despite considerable research efforts, the question about an optimal pathologist-based screening method for HLRCC-associated ULs remains unanswered.…”

Prevalence of somatic and germline mutations of Fumarate hydratase in uterine leiomyomas from young patients

“…This hospital‐based retrospective study revealed seven FH‐negative cases among 153 unselected leiomyomas from female patients aged up to 30 years. In keeping with recent findings, our study has demonstrated that FH‐deficient/mutated leiomyomas exhibit reproducible morphological features despite some degree of variation . This observation, as well as documented data in the literature, emphasises the rationale and importance of evaluation of potential HLRCC patients in a cost‐effective manner.…”

“…Unlike a low penetrance phenotype for RCCs, nearly all patients with FH‐deficient HLRCC syndrome present with early‐onset uterine leiomyomas that tend to be multiple, large and symptomatic, usually leading to myomectomy and even hysterectomy at less than 30 years of age . Importantly, characteristic morphological features common to FH‐deficient/mutated leiomyomas, including hypercellularity, eosinophilic hyaline globules, prominent nucleoli and perinucleolar halos, nuclear atypia, staghorn vasculature, fibrillary/neurophil‐like cytoplasm and alveolar oedema, have been reproducibly recognised . Given the high prevalence of leiomyoma specimens submitted for histopathological evaluation, evaluation for FH ‐ deficient/mutated leiomyomas by trained gynaecological pathologists and general surgical pathologists could identify patients with HLRCC at an earlier age and allow entry into surveillance prior to the development of aggressive, metastatic RCCs .…”