Prevalence of uterine and adnexal involvement in pulmonary lymphangioleiomyomatosis: a clinicopathologic study of 10 patients

Synergistic effects of mTOR inhibitors with VEGFR3 inhibitors on the interaction between TSC2-mutated cells and lymphatic endothelial cells

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease affecting the lung, kidney, and lymphatic system with a molecular mechanism of tuberous sclerosis complex 2 (TSC2) mutations. Vascular endothelial growth factor D (VEGF-D), a ligand for vascular endothelial growth factor receptor 3 (VEGFR3), is a diagnostic biomarker of LAM and is associated with lymphatic circulation abnormalities. This study explored the interaction between LAM cells and lymphatic endothelial cells (LECs) and the effects of rapamycin on this interaction, which may help to identify new targets for LAM treatment. This study used direct and indirect cocultures of TSC2-null cells and LECs. The xenograft model was applied to explore the therapeutic feasibility. Single-cell sequencing revealed increased LECs in the lungs of LAM patients through activation of pathways involved in lymphangiogenesis. TSC2-null cells attracted LECs and promoted tube formation. VEGF-D/VEGFR3 was a key mediator of the above interaction. Rapamycin can directly inhibit recruitment but not the tube formation of LECs in vitro. The combination of rapamycin with VEGFR3 inhibitors not only enhanced the effect of rapamycin but also inhibited lymphatic related manifestations including the tube formation and the lymphatic metastasis. Our findings demonstrated that LAM cells recruit LECs and promote tube formation via VEGF-D/VEGFR3. Rapamycin only partially blocked this interaction. The synergistic effects of rapamycin and VEGFR3 inhibitors suggest a novel strategy for the treatment of LAM and other TSC2-mutated diseases.

[Incidental diagnosis of lymphangioleiomyomatosis in gynecological surgery-a case series]

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a rare, slow progressing, low-grade neoplasia that primarily effects young women. The disease is well known for its pulmonary involvement with cystic destruction, but extra-pulmonary disease may occur. LAM is associated with mutations in the TSC 1 or TSC 2 genes and may develop sporadically or in the context of hereditary disease tuberous sclerosis complex (TSC). Incident LAM may represent the sentinel finding of the disease.

OBJECTIVE

Raising awareness for rare extrapulmonary LAM lesions in retroperitoneum and pelvic cavity.

METHODS

Data-based research was performed for LAM in gynecological surgical specimens. H&E-stained slides were re-examined, and immunohistochemical stains were re-evaluated. Clinical data were retrieved for the presence pulmonary LAM or TSC.

RESULTS

A total of 13 cases were identified. The age of the patients ranged from 32 to 77 years, and 8/13 were ≤ 55 years. Two women had a history of pulmonary LAM and TSC. Most women underwent surgery for gynecological malignancy. On histological examination, 10/13 patients presented LAM in 1 to 9 lymph nodes with a lesion size of 0.5 to 12.0 mm, mainly located subcapsular or in the nodal parenchyma. Three of the 13 women showed extranodal involvement of the retroperitoneum, myometrium, and the hilum of the ovary. Immunohistochemically LAM was positive for HMB45, desmin, and smooth muscle actin.

CONCLUSION

LAM is a rare systemic disease that mainly involves the lungs. Nevertheless, extra-pulmonary manifestations may occur. It is important to report the incidental finding of even small foci of LAM within the pathology report. Incidental LAM may represent the sentinel lesion for pulmonary LAM and/or TSC.

PEComas: A review of imaging and clinical features

Perivascular epithelioid cell tumors (PEComas) are a group of rare mesenchymal tumors, which demonstrate varied imaging appearances and treatment options. These tumors may arise de novo or in the setting of systemic disorders, such as tuberous sclerosis. Some PEComas are benign and easily resected while others may represent systemic or metastatic disease with limited therapeutic options. The purpose of this review is to introduce the topic of perivascular epithelioid cell tumors and the most common tumors within the PEComa family as well as discuss the epidemiology, morphology, radiographic appearance, and treatment options of these rare tumors.

Omics research in lymphangioleiomyomatosis: status and challenges

INTRODUCTION

Lymphangioleiomyomatosis (LAM) is a rare and progressive disorder that usually arises in the lung and almost exclusively affects women of childbearing age. In recent years, a number of molecules have been shown to be differentially expressed between patients with LAM and healthy control individuals, and some of these molecules, in addition to vascular endothelial growth factor D (VEGF-D), have the potential to be novel biomarkers.

AREAS COVERED

This review summarizes the recent advances in omics research, including genomics, transcriptomics, proteomics, and metabolomics, in LAM biomarker discovery. It also retrieves the literature on LAM biomarkers studied by omics techniques in the last 10 years using PubMed and other retrieval tools.

EXPERT OPINION

Further research on expanded sample sizes can be conducted to construct specific models to study the role of these molecules in the pathogenesis of LAM and clarify the underlying mechanisms involved. In the future, in terms of technology, the combination of various omics methods is expected to result in novel biomarker discovery.

Lymphangioleiomyomatosis and pregnancy: a mini-review

Lymphangioleiomyomatosis(LAM) is a slow progressive, rare cystic lung disease in women of reproductive age, associated with infiltration of the lung by atypical smooth muscle like cells, leading to the cystic destruction of the lung parenchyma. As LAM exclusively affects women of childbearing age, it can arise or exacerbate during pregnancy. Many patients with LAM are discouraged from pregnancy, although there is not much objective evidence effect on fertility. Patients diagnosed with LAM during pregnancy experience worse outcomes, so the safety of pregnancy is a vexing problem. What was worse, treatment strategies are limited on the effects of LAM on pregnancy outcomes. Pregnancy could be considered in LAM patients. Successful delivery in women with LAM depends on the condition of the LAM, which is in turn dependent on obstetricians and respiratory physicians. In this review, we describe the epidemiology, pathogenesis, diagnosis, clinical features and the treatment strategies of LAM during pregnancy.

A Case Report of Malignant Perivascular Epithelioid Cell Tumors of the Uterus and Literature Review

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors originating from perivascular epithelioid cells. In gynecological system, the uterus is one of the most common sites affected by PEComas. Most PEComas are benign, and patients usually have a good prognosis. However, malignant uterus PEComa is rare, and better comprehensive epidemiological investigations are needed. To date, there are a few reported cases of uterus PEComa. We herein report a rare case of malignant PEComa occurred in the uterine corpus and cervix, possibly accompanied by pulmonary lymphangioleiomyomatosis (PLAM). In addition, 55 cases of malignant uterus PEComa were picked out and collected in the data base of PubMed and Medline. On the one hand, the age of onset, population distribution, clinical manifestations, metastatic sites and routes of metastasis were analysed. On the other hand, a summary of the epidemiology, pathogenesis, diagnosis, and treatments of uterus PEComa was given.

Clinicopathological Impacts of Expression of Neuronal Markers in Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a tuberous sclerosis complex (TSC)-associated tumor, characterized by the expression of neural crest lineages including neuronal markers. Neural crest cells can differentiate into multiple cell types that contribute to tissues associated with TSC-related tumors, and TSC-related tumors could be specifically associated with distinct neural crest subtypes. This study aimed to clarify the clinicopathological effects of expression of neuronal markers in LAM. Lung tissues from 40 patients with LAM (of whom 13, 1, and 26 had undergone lung transplantation, lobectomy, and partial lung resection, respectively) were immunohistochemically analyzed. All patients were women, and their median age was 36 years (range: 24-62 y). All patients who underwent lung transplantation or lobectomy were classified as LAM histologic score (LHS)-3, whereas those who underwent partial lung resection were classified as LHS-1. LAM cells expressed peripherin (65%), and neuron-specific βIII-tubulin (43%). A comparison of the early (LHS-1) and advanced (LHS-3) stages of LAM revealed that neuron-specific βIII-tubulin was significantly expressed in the early stage of LAM ( P = 0.0009). Neuron-specific βIII-tubulin-positive LAM was associated with younger age ( P < 0.0001), the coexistence of renal angiomyolipoma ( P = 0.027), and the absence of retroperitoneal LAM ( P = 0.045). Furthermore, based on the expression levels of immunohistochemical markers in LAM, 2 distinct clusters with different expression levels of neuronal markers were observed. Approximately 40% to 60% of patients with LAM expressed neuron-specific βIII-tubulin and peripherin. Neuronal expression may be associated with disease severity.

A hint for abnormal thoracic shadow: look behind the heart

Can you diagnose this woman with a history of uterine fibroids in the previous year and a recent finding of intrathoracic mass on chest radiography? https://bit.ly/44mQ9Jj.

Single-cell multiomic analysis identifies a HOX-PBX gene network regulating the survival of lymphangioleiomyomatosis cells

Lymphangioleiomyomatosis (LAM) is a rare, progressive lung disease that predominantly affects women. LAM cells carry TSC1/TSC2 mutations, causing mTORC1 hyperactivation and uncontrolled cell growth. mTORC1 inhibitors stabilize lung function; however, sustained efficacy requires long-term administration, and some patients fail to tolerate or respond to therapy. Although the genetic basis of LAM is known, mechanisms underlying LAM pathogenesis remain elusive. We integrated single-cell RNA sequencing and single-nuclei ATAC-seq of LAM lungs to construct a gene regulatory network controlling the transcriptional program of LAM cells. We identified activation of uterine-specific HOX-PBX transcriptional programs in pulmonary LAMCORE cells as regulators of cell survival depending upon HOXD11-PBX1 dimerization. Accordingly, blockage of HOXD11-PBX1 dimerization by HXR9 suppressed LAM cell survival in vitro and in vivo. PBX1 regulated STAT1/3, increased the expression of antiapoptotic genes, and promoted LAM cell survival in vitro. The HOX-PBX gene network provides promising targets for treatment of LAM/TSC mTORC1-hyperactive cancers.

Estradiol Augments Tumor-Induced Neutrophil Production to Promote Tumor Cell Actions in Lymphangioleiomyomatosis Models

Lymphangioleiomyomatosis (LAM) is a rare cystic lung disease caused by smooth muscle cell-like tumors containing tuberous sclerosis (TSC) gene mutations and found almost exclusively in females. Patient studies suggest LAM progression is estrogen dependent, an observation supported by in vivo mouse models. However, in vitro data using TSC-null cell lines demonstrate modest estradiol (E2) responses, suggesting E2 effects in vivo may involve pathways independent of direct tumor stimulation. We previously reported tumor-dependent neutrophil expansion and promotion of TSC2-null tumor growth in an E2-sensitive LAM mouse model. We therefore hypothesized that E2 stimulates tumor growth in part by promoting neutrophil production. Here we report that E2-enhanced lung colonization of TSC2-null cells is indeed dependent on neutrophils. We demonstrate that E2 induces granulopoiesis via estrogen receptor α in male and female bone marrow cultures. With our novel TSC2-null mouse myometrial cell line, we show that factors released from these cells drive E2-sensitive neutrophil production. Last, we analyzed single-cell RNA sequencing data from LAM patients and demonstrate the presence of tumor-activated neutrophils. Our data suggest a powerful positive feedback loop whereby E2 and tumor factors induce neutrophil expansion, which in turn intensifies tumor growth and production of neutrophil-stimulating factors, resulting in continued TSC2-null tumor growth.

A Case of Uterine Lymphangioleiomyomatosis Complicated by Tuberous Sclerosis Complex

Lymphangioleiomyomatosis (LAM) is one of the presentations of perivascular epithelioid cell neoplasm that is frequently complicated by tuberous sclerosis complex (TSC). Here, we report an uncommon case of uterine LAM treated with everolimus, which is a mechanistic target of rapamycin (mTOR) inhibitor. A 42-year-old female patient (gravida 0) with a history of TSC presented with abdominal pain. Pelvic magnetic resonance imaging showed multiple masses in the uterine myometrium, suggesting tumors that may contain internal hemorrhagic components. The lesions were suspected as the root cause of her symptoms. After everolimus was administered for a previously diagnosed renal angiolipoma, her uterine tumors temporarily decreased in size. Subsequently, laparoscopic hysterectomy and bilateral salpingectomy were performed since she could not tolerate everolimus for a long period due to the medication's side effects. Furthermore, the patient was diagnosed with LAM through histopathological examination after surgical resection. Therefore, it is advisable to suspect and investigate uterine LAM when a patient with a history of TSC presents with irregular genital bleeding or abdominal pain. Moreover, mTOR inhibitors may be a treatment option, in addition to surgery, in cases of uterine LAM exacerbation.

Pelvic Lymph Node Lymphangiomyomatosis Found During Surgery for Gynecological Fallopian Tube Cancer: A Case Report and Literature Review

Background

Lymphangioleiomyomatosis (LAM) is a rare low-grade metastatic tumor with an unknown origin that spreads through lymphatic vessels. It is characterized by the proliferation of smooth muscle-like or epithelioid tumor cells in the lung and axial lymphatic system. Extrapulmonary LAM is a localized disease with a low incidence rate, and the location of the related lesions is atypical. It is difficult to diagnose. The LAM of pelvic lymph nodes is hidden. It is usually found through gynecological oncology surgery.

Case presentation

We report a 57-year-old postmenopausal woman with a pelvic mass and vaginal bleeding as the main symptoms. The patient had no history of pulmonary LAM, tuberous sclerosis complex (TSC), or renal angiomyolipoma and had not used exogenous hormones. We performed a total hysterectomy, bilateral adnexectomy, greater omentum resection, and pelvic lymphadenectomy under laparoscopy. The postoperative pathology confirmed high-grade serous carcinoma of the left fallopian tube, and four lymph nodes were found in the pelvic lymph nodes, suggesting lymphangiomyomatosis. Immunohistochemical results also showed that these cells could express markers of smooth muscle cells and melanoma cells. The patient was treated with chemotherapy after the operation. Chest CT did not suggest lung LAM during the postoperative follow-up, and there was no tumor recurrence.

Conclusion

The diagnosis of this disease is challenging. At the same time, due to insufficient clinical samples, it is still unknown whether there is a potential relationship between pelvic and peritoneal lymph node LAM found in the surgical staging of gynecological tumors and lung LAM and/or TSC. There is no evidence that pelvic and peritoneal lymph node LAM will increase the risk of pulmonary LAM. Therefore, additional clinical data are required to analyze and summarize the relationship between pelvic and peritoneal lymph node LAM, pulmonary LAM, and the source of LAM. We present a case of pelvic lymph node LAM and propose a hypothesis that the pathogenesis of endometriosis can be used for reference in the study of this disease.

Acute and repeated haemoperitoneum: a challenging case of lymphangioleiomyomatosis with uterine PEComa

A 39-year-old woman presented in the emergency ward for abdominal pain and acute anemiation. Abdominal-thoracic CT scan showed haemoperitoneum, with a parauterine mass and a pathological pulmonary pattern suspicious for lymphangioleiomyomatosis (LAM), a systemic disease belonging to perivascular epithelioid cell tumours (PEComas). Gynaecological ultrasound showed a hypoechoic irregular solid mass of the uterine right wall. Ultrasonographic virtual organ computer-aided analysis showed the mass completely formed by arteriovenous vessels, and that allowed distinction from leiomyosarcoma. Repeated haemoperitoneum required uterine artery embolisation. Mass revascularisation occurred in the following 7 days. A laparotomic hysterectomy with removal of the uterus and right parametrium was performed in epidural analgesia. Histological features were consistent with the diagnosis of uterine PEComa of uncertain malignant features, in the presence of coexisting pulmonary LAM. In women with LAM, acute haemoperitoneum may indicate the presence of a uterine PEComa whose diagnosis can be challenging.

Lymphangioleiomyomatosis: pathogenesis, clinical features, diagnosis, and management

Lymphangioleiomyomatosis (LAM) is a slowly progressive, low-grade, metastasising neoplasm of women, characterised by infiltration of the lung parenchyma with abnormal smooth muscle-like cells, resulting in cystic lung destruction. The invading cell in LAM arises from an unknown source and harbours mutations in tuberous sclerosis complex (TSC) genes that result in constitutive activation of the mechanistic target of rapamycin (mTOR) pathway, dysregulated cellular proliferation, and a programme of frustrated lymphangiogenesis, culminating in disordered lung remodelling and respiratory failure. Over the past two decades, all facets of LAM basic and clinical science have seen important advances, including improved understanding of molecular mechanisms, novel diagnostic and prognostic biomarkers, effective treatment strategies, and comprehensive clinical practice guidelines. Further research is needed to better understand the natural history of LAM; develop more powerful diagnostic, prognostic, and predictive biomarkers; optimise the use of inhibitors of mTOR complex 1 in the treatment of LAM; and explore novel approaches to the development of remission-inducing therapies.

Evidence for shared genetic risk factors between lymphangioleiomyomatosis and pulmonary function

Introduction

Lymphangioleiomyomatosis (LAM) is a rare low-grade metastasising disease characterised by cystic lung destruction. The genetic basis of LAM remains incompletely determined, and the disease cell-of-origin is uncertain. We analysed the possibility of a shared genetic basis between LAM and cancer, and LAM and pulmonary function.

Methods

The results of genome-wide association studies of LAM, 17 cancer types and spirometry measures (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC ratio and peak expiratory flow (PEF)) were analysed for genetic correlations, shared genetic variants and causality. Genomic and transcriptomic data were examined, and immunodetection assays were performed to evaluate pleiotropic genes.

Results

There were no significant overall genetic correlations between LAM and cancer, but LAM correlated negatively with FVC and PEF, and a trend in the same direction was observed for FEV1. 22 shared genetic variants were uncovered between LAM and pulmonary function, while seven shared variants were identified between LAM and cancer. The LAM-pulmonary function shared genetics identified four pleiotropic genes previously recognised in LAM single-cell transcriptomes: ADAM12, BNC2, NR2F2 and SP5. We had previously associated NR2F2 variants with LAM, and we identified its functional partner NR3C1 as another pleotropic factor. NR3C1 expression was confirmed in LAM lung lesions. Another candidate pleiotropic factor, CNTN2, was found more abundant in plasma of LAM patients than that of healthy women.

Conclusions

This study suggests the existence of a common genetic aetiology between LAM and pulmonary function.

Sporadic uterine Lymphangioleiomyomatosis (LAM): Report of a unique case arising in the lower uterine segment with short review

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Extrapulmonary lymphangioleiomyomatosis is rare and can be associated with tuberous sclerosis.

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Recognition of lymphangioleiomyomatosis is important for early disease screening and genetic testing.

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Lymphangioleiomyomatosis in lower uterine segment is very rare and can be overlooked.

Isolation and characterisation of lymphatic endothelial cells from lung tissues affected by lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare pulmonary disease characterised by the proliferation of smooth muscle-like cells (LAM cells), and an abundance of lymphatic vessels in LAM lesions. Studies reported that vascular endothelial growth factor-D (VEGF-D) secreted by LAM cells contributes to LAM-associated lymphangiogenesis, however, the precise mechanisms of lymphangiogenesis and characteristics of lymphatic endothelial cells (LECs) in LAM lesions have not yet been elucidated. In this study, human primary-cultured LECs were obtained both from LAM-affected lung tissues (LAM-LECs) and normal lung tissues (control LECs) using fluorescence-activated cell sorting (FACS). We found that LAM-LECs had significantly higher ability of proliferation and migration compared to control LECs. VEGF-D significantly promoted migration of LECs but not proliferation of LECs in vitro. cDNA microarray and FACS analysis revealed the expression of vascular endothelial growth factor receptor (VEGFR)-3 and integrin α9 were elevated in LAM-LECs. Inhibition of VEGFR-3 suppressed proliferation and migration of LECs, and blockade of integrin α9 reduced VEGF-D-induced migration of LECs. Our data uncovered the distinct features of LAM-associated LECs, increased proliferation and migration, which may be due to higher expression of VEGFR-3 and integrin α9. Furthermore, we also found VEGF-D/VEGFR-3 and VEGF-D/ integrin α9 signaling play an important role in LAM-associated lymphangiogenesis.

Lymphangioleiomyoma of the Uterus and Pelvic Lymph Nodes: A Report of 3 Cases, Including the Potentially Earliest Manifestation of Extrapulmonary Lymphangioleiomyomatosis

We present 3 cases of extrapulmonary lymphangioleiomyomatosis (LAM) identified incidentally in the uterine corpus and pelvic nodes resected for other reasons. One patient, a 47-yr-old female with corpus cancer, underwent a total hysterectomy and nodal dissection; the other 2 patients, aged 44 and 49 yr, underwent simple hysterectomy for corpus leiomyomas. None of the patients had evidence of tuberous sclerosis complex or any significant lesions in other organs. An area of spindle cell proliferation, intimately associated with dilated and tortuous lymphatic vessels, was found in the myometrium of all 3 patients, and nodal involvement with spindle cell proliferation was observed in the patient with corpus cancer. The spindle cells had faintly eosinophilic cytoplasm and a bland appearance. They were immunoreactive for α-SMA, gp100 (HMB45), and Melan-A. Tumor cell clusters lined with a single layer of lymphatic endothelium were floating in the lymphatic vessel lumen. These lesions were diagnosed as lymphangioleiomyoma in the uterine corpus and associated lymph nodes. Two of the cases seemed to be the earliest manifestations of extrapulmonary LAM, and the other case represents early-phase metastasis of LAM from the uterus. The present cases support the speculation that the uterus is the primary source of LAM cells.

Single-Cell Transcriptomic Analysis Identifies a Unique Pulmonary Lymphangioleiomyomatosis Cell

Rationale: Lymphangioleiomyomatosis (LAM) is a metastatic neoplasm of reproductive-age women associated with mutations in tuberous sclerosis complex genes. LAM causes cystic remodeling of the lung and progressive respiratory failure. The sources and cellular characteristics of LAM cells underlying disease pathogenesis remain elusive.Objectives: Identification and characterization of LAM cells in human lung and uterus using a single-cell approach.Methods: Single-cell and single-nuclei RNA sequencing on LAM (n = 4) and control (n = 7) lungs, immunofluorescence confocal microscopy, ELISA, and aptamer proteomics were used to identify and validate LAMCORE cells and secreted biomarkers, predict cellular origins, and define molecular and cellular networks in LAM.Measurements and Main Results: A unique cell type termed LAMCORE was identified, which was distinct from, but closely related to, lung mesenchymal cells. LAMCORE cells expressing signature genes included known LAM markers such as PMEL, FIGF, CTSK, and MLANA and novel biomarkers validated by aptamer screening, ELISA, and immunofluorescence microscopy. LAM cells in lung and uterus are morphologically indistinguishable and share similar gene expression profiles and biallelic TSC2 mutations, supporting a potential uterine origin for the LAMCORE cell. Effects of LAM on resident pulmonary cell types indicated recruitment and activation of lymphatic endothelial cells.Conclusions: A unique population of LAMCORE cells was identified in lung and uterus of patients with LAM, sharing close transcriptomic identity. LAM cell selective markers, secreted biomarkers, and the predicted cellular molecular features provide new insights into the signaling and transcriptional programs that may serve as diagnostic markers and therapeutic targets to influence the pathogenesis of LAM.

Perivascular epithelioid cell tumors (PEComa) of the gynecologic tract

PEComas of the female genital tract are rare mesenchymal neoplasms that are most common in the uterus, but also may occur in other gynecologic locations. As they morphologically and immunohistochemically resemble smooth muscle tumors, distinction between the two entities is often challenging, and may be aided by molecular analysis. Thus far, two distinct molecular groups-classic PEComas with TSC mutations and TFE3-translocation associated PEComas with TFE3 fusions have been described. Recognition of the first group is imperative as these patients may benefit from targeted therapy with mTOR inhibitors, if malignant. This review will focus on recognition of the morphologic and immunophenotypic features of PEComas, as well as the role of molecular testing in their diagnosis and treatment, analysis of the different algorithms to predict behavior, and differential diagnosis.

Sphingolipid, fatty acid and phospholipid metabolites are associated with disease severity and mTOR inhibition in lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a rare multisystem disease almost exclusively affecting women which causes loss of lung function, lymphatic abnormalities and angiomyolipomas. LAM occurs sporadically and in people with tuberous sclerosis complex (TSC). Loss of TSC gene function leads to dysregulated mechanistic target of rapamycin (mTOR) signalling. As mTOR is a regulator of lipid and nucleotide synthesis, we hypothesised that the serum metabolome would be altered in LAM and related to disease severity and activity.

METHODS

Ultrahigh performance liquid chromatography-tandem mass spectroscopy was used to examine the serum metabolome of 79 closely phenotyped women with LAM, including 29 receiving treatment with an mTOR inhibitor and 43 healthy control women.

RESULTS

Sphingolipid, fatty acid and phospholipid metabolites were associated with FEV₁ in women with LAM (eg, behenoyl sphingomyelin adjusted (adj.) p=8.10 × 10^-3). Those with higher disease-burden scores had abnormalities in fatty acid, phospholipid and lysolipids. Rate of loss of FEV₁ was associated with differences in acyl-carnitine, acyl-glycines, acyl-glutamine, fatty acids, endocanbinoids and sphingolipids (eg, myristoleoylcarnitine adj. p=0.07). In TSC-LAM, rapamycin affected modules of interrelated metabolites which comprised linoleic acid, the tricarboxylic acid cycle, aminoacyl-tRNA biosynthesis, cysteine, methionine, arginine and proline metabolism. Metabolomic pathway analysis within modules reiterated the importance of glycerophospholipid metabolites (adj. p=0.047).

CONCLUSIONS

Women with LAM have altered lipid metabolism. The associations between these metabolites, multiple markers of disease activity and their potential biological roles in cell survival and signalling, suggest that lipid species may be both disease-relevant biomarkers and potential therapeutic targets for LAM.

Neutrophil elastase from myeloid cells promotes TSC2-null tumor growth

Chronic inflammation promotes progression of many cancers, with circulating myeloid-derived suppressor cell (MDSC) levels correlating with poor prognosis. Here we examine effects of MDSCs on lymphangioleiomyomatosis (LAM), a rare disease occurring almost exclusively in women whereby estrogen-sensitive metastatic TSC2-null tumors grow throughout the lungs, markedly reducing pulmonary function. The LAM cell origin remains unknown; however, previous work demonstrated that Tsc2 inactivation in the mouse uterus induced estrogen-dependent myometrial tumors with nearly all features of LAM. Half of these animals developed metastatic myometrial tumors in the lungs, suggesting that LAM cells might originate from the myometrium, possibly explaining its overwhelming female prevalence and estrogen-sensitivity. Here we report that MDSC levels, and in particular granulocytic myeloid cell levels, are elevated in the periphery and in tumors of uterine-specific Tsc2-null mice. Importantly, MDSC depletion or inhibition of their recruitment impairs myometrial tumor growth. RNA and protein analysis of Tsc2-null myometrial tumors and xenografts demonstrate high expression and activity of the serine protease neutrophil elastase (NE), with selective qPCR studies indicating a stromal origin of the NE. Notably, treatment with sivelestat, a known NE inhibitor already approved for human use in some countries, reduces tumor growth similar to MDSC depletion. Furthermore, NE promotes Tsc2-null tumor cell growth, migration, and invasion in vitro. Finally, NE-expressing myeloid cells are present throughout the lungs of LAM patients but not controls. These data suggest that NE derived from granulocytic myeloid cells might directly promote LAM tumor cell progression and could be a novel therapeutic target for LAM.

Isolated sporadic uterine lymphangioleiomyoma with unusual clinical and pathological features

We report a unique uterine neoplasm, favoured to represent an isolated extrapulmonary lymphangioleiomyoma with unusual pathological features, in a postmenopausal woman without tuberous sclerosis complex. The large neoplasm consisted of smooth muscle fascicles and cystic spaces lined by lymphatic cells, which were negative for the melanocytic staining that is characteristically positive in lymphangioleiomyomatosis (LAM). There are fewer than 30 cases of uterine LAM reported, none of which have demonstrated this morphology or these immunohistochemical findings. The origin of LAM cells in the more typical pulmonary LAM remains unclear; the unusual features in this case may represent a distinct pathological entity or a rare variant of typical extrapulmonary LAM, and may contribute to determining the cellular origin of these rare tumours. Conversely, this may represent a case of 'prepulmonary' LAM, providing supporting evidence for a possible gynaecological origin of these tumours in the broader affected (almost exclusively female) population.

Pulmonary lymphangioleiomyomatosis: A proposed state of neoplastic senescence

Pulmonary lymphangioleiomyomatosis (PLAM) is a disease strongly associated with tuberous sclerosis. In PLAM patients, with and without clinical tuberous sclerosis, mutations in the tuberous sclerosis complex involving the proteins hamartin and tuberin have been found. These proteins are key regulators of the mTOR pathway. mTOR activation is a key step in normal cellular senescence. The hypothesis proposed here is that mutations in the tuberous sclerosis complex leading to mTOR activation result in the specialized LAM cells acquiring many of the cellular characteristics of the normal senescent cell, a state that I propose to characterize as a state of neoplastic senescence. Using this hypothesis as a theoretical basis, many of the enigmatic features of the pathogenesis and clinical behavior of PLAM can be explained. In addition, the hypothesis may lead to new insights into possible therapeutic interventions for this disease.

Uterine PEComas: A Morphologic, Immunohistochemical, and Molecular Analysis of 32 Tumors

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms that may show overlapping morphology and immunohistochemistry with uterine smooth muscle tumors. In this study, we evaluated the morphologic, immunohistochemical, and molecular features of 32 PEComas, including 11 with aggressive behavior. Two distinct morphologies were observed: classic (n=30) and those with a lymphangioleiomyomatosis appearance (n=2). In the former, patients ranged from 32 to 77 (mean: 51) years and 13% had tuberous sclerosis. Tumors ranged from 0.2 to 17 (mean: 5.5) cm with 77% arising in the corpus. Epithelioid cells were present in 100% and a spindled component was seen in 37%. Nuclear atypia was low (53%), intermediate (17%), or high (30%). Mitoses ranged from 0 to 36 (mean: 6) and 0 to 133 (mean: 19) per 10 and 50 high-power fields, with atypical mitoses present in 30%. Thin and delicate vessels were noted in 100%, clear/eosinophilic and granular cytoplasm in 93%, stromal hyalinization in 73%, necrosis in 30%, and lymphovascular invasion in 10%. All tumors were positive for HMB-45, cathepsin K, and at least one muscle marker, with most expressing melan-A (77%) and/or MiTF (79%). A PSF-TFE3 fusion was identified in one while another showed a RAD51B-OPHN1 fusion. Follow-up ranged from 2 to 175 (mean: 41) months, with 63% of patients alive and well, 20% dead of disease, 13% alive with disease, and 3% dead from other causes. In the latter group (n=2), patients were 39 and 49 years old, one had tuberous sclerosis, while the other had pulmonary lymphangioleiomyomatosis. Both tumors expressed HMB-45, cathepsin K, and muscle markers, but lacked TFE3 and RAD51B rearrangements. The 2 patients are currently alive and well. Application of gynecologic-specific criteria (≥4 features required for malignancy: size ≥5 cm, high-grade atypia, mitoses >1/50 high-power fields, necrosis, and lymphovascular invasion) for predicting outcome misclassified 36% (4/11) of aggressive tumors; thus, a modified algorithm with a threshold of 3 of these features is recommended to classify a PEComa as malignant.

Risk of breast cancer in patients with lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare metastasizing pulmonary disease that shares some clinical, cellular, and molecular similarities with metastatic breast cancer to lung. LAM cells have been identified circulating in various body fluids of patients and, intriguingly, diverse evidence indicates that these cells may originate from a different organ to the lung. Following on from these observations, we hypothesized the existence of a common risk basis between LAM and breast cancer, and suggested increased risk of breast cancer among LAM patients. Here, by studying two additional LAM cohorts with more detailed epidemiological, life-style, and disease-related data, we show consistent results; a potential excess of estrogen-receptor-positive young breast cancer cases in LAM. This observation further suggests the need of prospective studies to precisely assess the association between both diseases.

MR findings of uterine PEComa in patients with tuberous sclerosis: report of two cases

Tuberous sclerosis complex (TSC), a rare autosomal dominant neurocutaneous disorder, is characterized by the presence of benign congenital tumors in multiple organs. Neoplasms with perivascular epithelioid cell differentiation (PEComas), including angiomyolipoma (AML) and lymphangioleiomyomatosis (LAM), can occur in association with TSC. This report describes two cases of uterine PEComas presenting characteristic MR imaging features reflecting pathological findings. From MR images, both cases showed single or multiple large, irregularly shaped or lobulated hemorrhagic lesions within the myometrium. They differed from typical adenomyotic cysts in their large size and irregular margins. Histopathologic analysis revealed that the hemorrhage was caused by adenomyosis and tumor cells that proliferated in surrounding stroma of the hemorrhagic lesions, compatible with PEComas. Microscopic observation revealed an infiltrative growth pattern of PEComas, with small nodules formed. The tumor lesions, however, were difficult to detect on MR images. The myometrium showed normal appearance on both T1-weighted and T2-weighted images in both cases. We speculate that PEComas may infiltrate extensively into the myometrium even when the myometrium shows almost normal radiologic appearance.

Extrapulmonary uterine lymphangioleiomyomatosis (LAM) and dysfunctional uterine bleeding: the first presentation of LAM in a tuberous sclerosis complex patient

Lymphangioleiomyomatosis (LAM) is a rare disease that typically affects women of childbearing age. It most commonly affects the lungs (P-LAM) but can occasionally occur in extra-pulmonary sites (E-LAM). There is a strong association between LAM and the tuberous sclerosis complex (TSC). We report a case of a 42-year-old female TSC sufferer who presented with dysfunctional uterine bleeding. She was not known to have LAM. An endometrial biopsy revealed a spindled-cell lesion suspicious of leiomyosarcoma, which correlated with cross-sectional imaging. She underwent a hysterectomy that showed a bizarre (symplastic) leiomyomatous endometrial polyp with background uterine LAM. We discuss the clinical and pathological implications of this unusual case of E-LAM and the importance of clinicopathological correlation in TSC sufferers. The association of uterine LAM with TSC is important and LAM should be considered as a differential of dysfunctional uterine bleeding and a benign mimic to uterine leiomyosarcoma in patients with TSC.

Clinicopathological analysis of clinically occult extrapulmonary lymphangioleiomyomatosis in intra-pelvic and para-aortic lymph nodes associated with pelvic malignant tumors: A study of nine patients

The clinicopathological and immunohistochemical characteristics of clinically occult extrapulmonary lymphangioleiomyomatosis in lymph nodes (LN-LAM) being dissected during surgical staging of pelvic malignancy have not been well investigated. We assessed samples from nine female patients (median age, 61). None had past or familial history of tuberous sclerosis and had LAM lesions other than LN such as lung. The primary malignancies included four endometrial endometrioid carcinomas, one endometrial carcinosarcoma, three ovarian serous carcinomas and one urothelial carcinoma. Median follow-up was 43 months. The number of affected LNs ranged from 1 to 15 (median, 2) with sizes ranging from 1 to 13 mm (median, 3.0). Six cases had clinically occult LN-LAM only within the pelvic LNs, two only within para-aortic LNs, and one within both pelvic and para-aortic lymph nodes. Immunohistochemically, LAM cells exhibited a strong diffuse positivity for β-catenin and E-cadherin in all nine cases. Clinically occult LN-LAM mainly affects peri- or post-menopausal women. On rare occasions, occult LN-LAM may manifest as systemic LAM, including in the lung. β-catenin and E-cadherin carry potential utility as additional diagnostic markers.

Diagnostic management of occult nodal lymphangioleiomyomatosis detected during pelvic cancer staging. Localized finding or systemic disease?

Background

Lymphangioleiomyomatosis (LAM) is a neoplastic disease that generally arises in the lung (pLAM) and may be associated with "Tuberous sclerosis complex" (TSC). Occasionally, LAM can arise at the extrapulmonary sites (eLAM), such as the mediastinum, the retroperitoneum or the lymph nodes. 25-30% of the patients affected by pLAM develop eLAM. In asymptomatic patients, the presence of mediastinal and retroperitoneal eLAM preceded that of pLAM by usually 1-2 years. Nevertheless, some authors reported that the nodal eLAM, detected during pelvic cancer staging, arise in patents without pLAM and/or TSC. In this paper we review the Literature of this rare condition suggesting its diagnostic management.

Results

To date, it has been reported 30 cases. The mean age at diagnosis is 55 years and around 30% of patients are postmenopausal. In only 2 cases was diagnosed a following p-LAM. One patient with endometrioid carcinoma and pelvic nodal eLAM reported TSC2 germiline mutation. None case was associated with both p-LAM and TSC.

Conclusions

The retrospective probability to have p-LAM in patients with staging pelvic nodal e-LAM is 6,6% (4/30) lower than the probability to have e-LAM in patients affected by p-LAM (25-30%). In both this association is more probable sporadically than associated with TSC. The association between cancer staging pelvic nodal e-LAM and TSC is low (3%; 1/30). The p-LAM developed are asymptomatic with a behavior, regardless of hormonal status, similar to lesions diagnosed in postmenopausal although further studies are mandatory to confirm it.

A case of uterine lymphangioleiomyomatosis in a young woman that was identified via peritonitis

Although lymphangioleiomyomatosis is often observed with tuberous sclerosis, uterine lymphangioleiomyomatosis is rare. Our patient was 36 years old (gravida 0, para 0). She had a history of tuberous sclerosis, and many myometrial cystic lesions were identified during assisted reproductive therapy. Although we administered a gonadotropin-releasing hormone analog, myometrial cystic lesions increased in size. Therefore, simple hysterectomy, bilateral salpingo-oophorectomy and pelvic lymph node biopsy were performed. Postoperative histology showed lymphangioleiomyomatosis and myometrial abscess. For uterine lesions in young women with tuberous sclerosis, the possibility of uterine lymphangioleiomyomatosis should also be considered.

Incidental lymphangioleiomyomatosis in the lymph nodes of gynecologic surgical specimens

OBJECTIVES

Incidentally discovered lymphangioleiomyomatosis (LAM) in sampled lymph nodes are infrequent but intractable issues for gynecologists. The aims of this study were to elucidate the prevalence of incidental nodal LAM in a consecutive cohort of gynecologic surgical specimens from Japanese patients, to document clinicopathological features of nodal LAM cases, and to investigate the association between the subsequent development of pulmonary LAM and tuberous sclerosis complex (TSC).

STUDY DESIGN

We retrospectively reviewed 1732 consecutive Japanese patients who underwent gynecologic surgery with lymph node sampling in the National Cancer Center Hospital between January 2004 and April 2017. The pathological diagnosis of LAM was performed by pathologists. Clinicopathological data were obtained from patients' electronic medical records.

RESULTS

We found that 0.46% (8/1732) of gynecologic surgical specimens with lymph node sampling showed incidental nodal LAM. The size of the lesions was less than 10 mm, and external iliac and obturator nodes were frequently affected. Although there has been no report of a case of incidental nodal LAM developing pulmonary LAM, we identified the first case of a 36-year-old woman who developed pulmonary LAM 7 years after the diagnosis of incidental nodal LAM. None of the 8 patients had a personal or family history of TSC.

CONCLUSIONS

Our case brings attention to the risk of developing subsequent pulmonary LAM. To date, insufficient long-term follow-up data of young patients have hindered us from drawing a definite conclusion that patients with incidental nodal LAM are not at risk for subsequent pulmonary LAM. Future studies should collect and share long-term follow-up data to elucidate the true risk of developing pulmonary LAM in women with incidental nodal LAM.

The Lymphangioleiomyomatosis Lung Cell and Its Human Cell Models

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, affecting lungs, kidneys, and lymphatics. It is caused by the proliferation of abnormal smooth muscle-like LAM cells, with mutations and loss of heterozygosity in the TSC1 or, more frequently, TSC2 genes. Isolated pulmonary LAM cells have been difficult to maintain in culture, and most studies of LAM lung cells involve mixtures of TSC2 wild-type and TSC2-null cells. A clonal population of LAM lung cells has not been established, making analysis of the cells challenging. Cell lines have been established from angiomyolipomas, a common manifestation of LAM, and from tumors from patients with TSC. Circulating LAM cells have also been isolated from blood and other body fluids. LAM cells may also be identified in clusters apparently derived from lymphatic vessels. Genetics, patterns of antigen expression, and signaling pathways have been studied in LAM lung tissue and in LAM cell models, although rarely all in the same study. We show here that LAM cells manifest differences in these characteristics, depending on the source investigated, suggesting further studies.

Uterine Mesenchymal Tumors: Hereditary Aspects

The topic of hereditary gynecologic malignancies readily evokes associations between Lynch syndrome and endometrial adenocarcinoma, or between BRCA mutations and tubo-ovarian serous carcinoma, but other familial associations are less well-known. Two hereditary syndromes are known to be related to uterine mesenchymal tumors: hereditary leiomyomatosis and renal cell carcinoma syndrome and the tuberous sclerosis complex. In the following review, we describe the current literature on these syndromes, summarizing their clinical, morphologic, immunophenotypic, and genetic data. It is possible that the surgical pathologic diagnosis is the first indication of a familial syndrome, thus emphasizing the importance of a pathologist's familiarity with these potentially suggestive lesions.

Uncommon hereditary gynaecological tumour syndromes: pathological features in tumours that may predict risk for a germline mutation

The most common hereditary gynaecological tumour syndromes are hereditary breast and ovarian cancer syndrome and Lynch syndrome. However, pathologists also may encounter gynaecological tumours in women with rare hereditary syndromes. Many of these tumours exhibit distinctive gross and microscopic features that are associated with a risk for an inherited gene mutation. The sensitivity and specificity of these tumour pathology features for predicting an inherited mutation vary depending on the syndrome. By recognising these tumour features, pathologists may potentially contribute to the diagnosis of an unsuspected syndrome by recommending referral of the patient for formal risk assessment by genetic counselling. Patients additionally benefit from diagnosis of an inherited syndrome because many also carry a lifetime risk for developing primary malignancies outside of the gynaecological tract. Early diagnosis of an inherited syndrome permits early screening, detection, and management of additional malignancies associated with the syndrome. This review highlights these rare syndromes and their tumour pathology, including Peutz-Jeghers syndrome (gastric type mucinous carcinoma of the cervix; ovarian sex cord tumour with annular tubules); hereditary leiomyoma renal cell carcinoma syndrome (uterine leiomyoma); tuberous sclerosis complex (uterine PEComa; uterine lymphangioleiomyomatosis); DICER1 syndrome (ovarian Sertoli-Leydig cell tumour; cervical embryonal rhabdomyosarcoma); rhabdoid tumour predisposition syndrome 2 (small cell carcinoma of the ovary, hypercalcaemic type); Cowden syndrome (endometrial endometrioid adenocarcinoma); naevoid basal cell carcinoma syndrome (ovarian fibroma); and Von Hippel-Lindau syndrome (clear cell papillary cystadenoma of the broad ligament).

Diagnosis and treatment of cystic lung disease

Cystic lung disease (CLD) is a group of lung disorders characterized by the presence of multiple cysts, defined as air-filled lucencies or low-attenuating areas, bordered by a thin wall (usually < 2 mm). The recognition of CLDs has increased with the widespread use of computed tomography. This article addresses the mechanisms of cyst formation and the diagnostic approaches to CLDs. A number of assessment methods that can be used to confirm CLDs are discussed, including high-resolution computed tomography, pathologic approaches, and genetic/ serologic markers, together with treatment modalities, including new therapeutic drugs currently being evaluated. The CLDs covered by this review are lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dube syndrome, lymphocytic interstitial pneumonia/follicular bronchiolitis, and amyloidosis.

Lymphangioleiomyomatosis

Lymphangioleiomyomatosis is a rare multisystem disease predominantly affecting women that can occur sporadically or in association with tuberous sclerosis. Lung cysts progressively replace the lung parenchyma, which leads to dyspnea, recurrent pneumothorax, and in some cases respiratory failure. Patients may also have lymphatic disease in the thorax, abdomen, and pelvis, and renal angiomyolipomas. Treatment includes supportive care, bronchodilators, and for those with progressive disease, mammalian target of rapamycin (mTOR) inhibitors.

Minireview: Lymphangioleiomyomatosis (LAM): The "Other" Steroid-Sensitive Cancer

Lymphangioleiomyomatosis (LAM) is a devastating rare lung disease affecting primarily childbearing age women in which tumors consisting of abnormal smooth-muscle-like cells grow within the lungs and progressively lead to loss of pulmonary function. LAM cells metastasize to the lungs, predominantly through the lymphatics; however, the source of the LAM cell is still unknown. LAM cells contain inactivating mutations in genes encoding tuberous sclerosis 1 or 2, proteins that normally limit cell growth through suppression of mammalian target of rapamycin complex 1. As of today, sirolimus (an mammalian target of rapamycin complex 1 inhibitor) is the only treatment, available for LAM patients that is approved by the Food and Drug Administration; however, this drug and others in its class provide stabilization but not remission of LAM. One of the biggest problems in treating LAM is that both the origin of the LAM cells and the mechanism of the sexual dimorphism in LAM are still not understood. LAM cells express estrogen and progesterone receptors, and lung function declines during periods of high circulating estrogen levels. Moreover, numerous basic research studies find that estrogen is a key driving force in LAM cell proliferation, migration, and metastasis. In this review, we highlight recent insights regarding the role of steroid hormones in LAM and discuss possible explanations for the profound female sexual dimorphism of LAM.

Nonmalignant Adult Thoracic Lymphatic Disorders

The thoracic lymphatic disorders are a heterogeneous group of uncommon conditions that are associated with thoracic masses, interstitial pulmonary infiltrates, and chylous complications. Accurate diagnosis of the thoracic lymphatic disorders has important implications for the newest approaches to management, including embolization and treatment with antilymphangiogenic drugs. New imaging techniques to characterize lymphatic flow, such as dynamic contrast-enhanced magnetic resonance lymphangiogram, are redefining approaches to disease classification and therapy.

Gynecologic Manifestations of Less Commonly Encountered Hereditary Syndromes

This review covers gynecologic manifestations that may occur in rare hereditary syndromes. Recent advances in disorders, such as hereditary leiomyomatosis, renal cell carcinoma syndrome and tuberous sclerosis complex, are discussed as well as lesions that occur in von Hippel-Lindau syndrome, nevoid basal cell carcinoma syndrome, Cowden syndrome, Ollier disease/Maffucci syndrome, and Carney complex. Characteristic clinicopathologic features of each of these syndromes are discussed with an emphasis on the key features that enable pathologists to identify patients at highest risk for these diseases.

Estrogen maintains myometrial tumors in a lymphangioleiomyomatosis model

Lymphangioleiomyomatosis (LAM) is a rare disease in women. Patients with LAM develop metastatic smooth-muscle cell adenomas within the lungs, resulting in reduced pulmonary function. LAM cells contain mutations in tuberous sclerosis genes (TSC1 or TSC2), leading to up-regulation of mTORC1 activity and elevated proliferation. The origin of LAM cells remains unknown; however, inactivation of Tsc2 gene in the mouse uterus resulted in myometrial tumors exhibiting LAM features, and approximately 50% of animals developed metastatic myometrial lung tumors. This suggests that LAM tumors might originate from the uterine myometrium, possibly explaining the overwhelming prevalence of LAM in female. Here, we demonstrate that mouse Tsc2-null myometrial tumors exhibit nearly all the features of LAM, including mTORC1/S6K activation, as well as expression of melanocytic markers and matrix metalloproteinases (MMPs). Estrogen ablation reduces S6K signaling and results in Tsc2-null myometrial tumor regression. Thus, even without TSC2, estradiol is required to maintain tumors and mTORC1/S6K signaling. Additionally, we find that MMP-2 and -9, as well as neutrophil elastase (NE), are overexpressed in Tsc2-null myometrial tumors in an estrogen-dependent fashion. In vivo fluorescent imaging using MMP- or NE-sensitive optical biomarkers confirms that protease activity is specific to myometrial tumors. Similar to LAM cells, uterine Tsc2-null myometrial cells also overexpress melanocytic markers in an estrogen-dependent fashion. Finally, we identify glycoprotein NMB (GPNMB) as a melanocytic marker up-regulated in Tsc2-null mouse uteri and human LAM samples. Our data highlight the potential importance of estradiol in LAM cells, suggesting that anti-estrogen therapy may be a treatment modality. Furthermore, proteases and GPNMB might be useful LAM biomarkers.

EPIDEMIOLOGY, PATHOGENESIS and DIAGNOSIS of LYMPHANGIOLEIOMYOMATOSIS

INTRODUCTION

Lymphangioleiomyomatosis (LAM) is a disease of women characterized by cystic lung destruction, lymphatic involvement, and renal angiomyolipomas.

AREAS COVERED

LAM is caused by proliferation of abnormal smooth muscle-like LAM cells containing mutations and perhaps epigenetic modifications of the TSC1 or TSC2 genes, which encode, respectively, hamartin and tuberin, two proteins controlling the mechanistic target of rapamycin (mTOR) signaling pathway. LAM occurs sporadically or in association with tuberous sclerosis complex. LAM may present with dyspnea, recurrent pneumothorax or chylothorax. Pulmonary function tests show reduced flow rates and lung diffusion capacity. Exercise testing may reveal hypoxemia and ventilatory limitation. The severity and progression of disease may be assessed by computer tomography, and pulmonary function and exercise testing. mTOR inhibitors, (e.g., sirolimus) are effective in stabilizing lung function, and reducing the size of chylous effusions, lymphangioleiomyomas, and angiomyolipomas.

EXPERT OPINION

Different clinical phenotypes including variable rates of disease progression and variable responses to therapy are seen in LAM patients. No one test is available that predicts the course of disease at the time of diagnosis. Further research regarding the molecular biology of LAM clinical phenotypes is warranted. Recent advances in the characterization of the pathogenesis of LAM are leading to the development of new therapies.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.