Clinicopathological analysis of multifocal micronodular pneumocyte hyperplasia associated with tuberous sclerosis in Japan

Lymphangioleiomyomatosis as a potent lung cancer risk factor: Insights from a Japanese large cohort study

BACKGROUND AND OBJECTIVE

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease associated with the functional tumour suppressor genes TSC1 and TSC2 and causes structural destruction in the lungs, which could potentially increase the risk of lung cancer. However, this relationship remains unclear because of the rarity of the disease.

METHODS

We investigated the relative risk of developing lung cancer among patients diagnosed with LAM between 2001 and 2022 at a single high-volume centre in Japan, using data from the Japanese Cancer Registry as the reference population. Next-generation sequencing (NGS) was performed in cases where tumour samples were available.

RESULTS

Among 642 patients diagnosed with LAM (sporadic LAM, n = 557; tuberous sclerosis complex-LAM, n = 80; unclassified, n = 5), 13 (2.2%) were diagnosed with lung cancer during a median follow-up period of 5.13 years. All patients were female, 61.5% were never smokers, and the median age at lung cancer diagnosis was 53 years. Eight patients developed lung cancer after LAM diagnosis. The estimated incidence of lung cancer was 301.4 cases per 100,000 person-years, and the standardized incidence ratio was 13.6 (95% confidence interval, 6.2-21.0; p = 0.0008). Actionable genetic alterations were identified in 38.5% of the patients (EGFR: 3, ALK: 1 and ERBB2: 1). No findings suggested loss of TSC gene function in the two patients analysed by NGS.

CONCLUSION

Our study revealed that patients diagnosed with LAM had a significantly increased risk of lung cancer. Further research is warranted to clarify the carcinogenesis of lung cancer in patients with LAM.

[Genetic diffuse cystic lung disease in adults]

Multiple cystic lung diseases comprise a wide range of various diseases, some of them of genetic origin. Lymphangioleiomyomatosis (LAM) is a disease occurring almost exclusively in women, sporadically or in association with tuberous sclerosis complex (TSC). Patients with LAM present with lymphatic complications, renal angiomyolipomas and cystic lung disease responsible for spontaneous pneumothoraces and progressive respiratory insufficiency. TSC and LAM have been ascribed to mutations in TSC1 or TSC2 genes. Patients with TSC are variably affected by cutaneous, cognitive and neuropsychiatric manifestations, epilepsy, cerebral and renal tumors, usually of benign nature. Birt-Hogg-Dubé syndrome is caused by mutations in FLCN encoding folliculin. This syndrome includes lung cysts of basal predominance, cutaneous fibrofolliculomas and various renal tumors. The main complications are spontaneous pneumothoraces and renal tumors requiring systematic screening. The mammalian target of rapamycin (mTOR) pathway is involved in the pathophysiology of TSC, sporadic LAM and Birt-Hogg-Dubé syndrome. MTOR inhibitors are used in LAM and in TSC while Birt-Hogg-Dubé syndrome does not progress towards chronic respiratory failure. Future challenges in these often under-recognized diseases include the need to reduce the delay to diagnosis, and to develop potentially curative treatments. In France, physicians can seek help from the network of reference centers for the diagnosis and management of rare pulmonary diseases.

Recurrent pneumothoraces with diffuse small ground-glass and solid nodules

Multifocal micronodular pneumocyte hyperplasia (MMPH) is the lesser known pulmonary manifestation of tuberous sclerosis. It manifests radiologically as diffuse small ground-glass and solid nodules. Accurate diagnosis is essential as it can be mistaken for miliary tuberculosis or malignant lesions which necessitates specific treatment. Constellation of radiological features such as multicentric disease at onset and stability over time can help to distinguish MMPH from its differentials. Histologically, MMPH is characterized by hamartomatous proliferation of type II pneumocytes with a lack of high nuclear to cytoplasmic ratio. MMPH confers a benign prognosis unlike its differentials. Therefore, accurate diagnosis is paramount in ensuring appropriate care is delivered. Here, we describe the radiological and histological features of MMPH in a patient with genetically proven tuberous sclerosis complex and co-existing lymphangioleiomyomatosis.

Novel genetic characteristics of multifocal micronodular pneumocyte hyperplasia (MMPH): a case report with frequent BRAF mutations analyzed by next-generation sequencing supporting benign behaviors of MMPH

A woman in her 30s, who was clinically diagnosed with tuberous sclerosis complex, underwent lung transplantation due to lymphangioleiomyomatosis with concomitant multifocal micronodular pneumocyte hyperplasia (MMPH). Histologically, MMPH lesions demonstrated variety in histology; some showed homogenous cells with mild nuclear atypia and elastic fibers proliferation, and the others showed enlarged nuclei without elastic fibers. Because the natural history of MMPH is not well characterized, we used next-generation sequencing to perform a comprehensive genetic analysis for the MMPH lesions to explore their malignant potential. Regardless of their histological variety, three of four lesions had BRAF missense mutations, especially the types frequently detected in atypical adenomatous hyperplasia that is considered to be benign rather than a precursor of adenocarcinoma. None of them had major driver mutations of lung adenocarcinoma, except for BRAF mutations. In conclusion, our study of the lesions from this patient indicated the benign characteristic of MMPH.

Effect of everolimus on multifocal micronodular pneumocyte hyperplasia in tuberous sclerosis complex

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a benign proliferation of alveolar type II cells presenting as multiple pulmonary nodules at chest imaging, which is frequently seen in patients with tuberous sclerosis complex (TSC). We report a case of a woman with TSC and MMPH who received everolimus, a mechanistic target of rapamycin (mTOR) inhibitor, for the treatment of a subependymal giant cell astrocytoma (SEGA). After 3 months of therapy, a remarkable decrease in density of all pulmonary MMPH lesions was observed, without any change in size. This shows that everolimus is active on MMPH similarly to its effects on SEGA, renal angiomyolipomas, and pulmonary lymphangioleiomyomatosis in TSC, and suggests that the dysregulated activation of mTOR which characterizes TSC also plays a role in the pathogenesis of MMPH.

Familial multifocal micronodular pneumocyte hyperplasia with a novel splicing mutation in TSC1: Three cases in one family

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare pulmonary disease, generally manifesting as a tuberous sclerosis complex (TSC), characterised by multiple, small ground-glass nodular shadows on chest computed tomography (CT). Histological examination typically reveals multicentric, well-demarcated, nodular type II pneumocystic growth. Herein, we describe three cases of this rare pulmonary disease occurring within one family. Using reverse transcription polymerase chain reaction (RT-PCR) and direct DNA sequencing, we identified a novel germline mutation, a point mutation in TSC1 intron 5, which yielded a splice variant and loss of function of TSC1. Furthermore, immunohistochemical staining indicated the expression of phospho-p70S6K and phospho-4E-BP1, suggesting that TSC1 function was impaired by the novel gene mutation in MMPH cells.

Clinical Course of Histologically Proven Multifocal Micronodular Pneumocyte Hyperplasia in Tuberous Sclerosis Complex: A Case Series and Comparison with Lymphangiomyomatosis

BACKGROUND

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare pulmonary manifestation of tuberous sclerosis complex (TSC). Because of its rarity, no previous study has described the detailed clinical course of this disease.

OBJECTIVES

This study aimed to clarify the longitudinal clinical characteristics of subjects with MMPH.

METHODS

Nine patients with MMPH diagnosed at Hokkaido University Hospital were retrospectively analyzed. Changes in computed tomography findings and pulmonary function were compared during the follow-up period. Serum levels of KL-6, surfactant protein (SP)-A, and SP-D were measured to clarify their potentials as blood biomarkers of the disease. Fourteen cases of lymphangiomyomatosis (LAM) were also included to compare their clinical characteristics with those of subjects with MMPH.

RESULTS

Of the 9 patients, 7 were female and 2 were male. The median age at diagnosis was 43 years (range, 19-56), and all cases were diagnosed following incidental abnormal radiographic findings. During the follow-up, 1 patient died of lung cancer, but others were radiographically stable and had stable pulmonary function. Serum levels of SP-A in 5 patients (mean, 146.4 ng/mL) and SP-D in 6 patients (mean, 337.3 ng/mL) were elevated in subjects with MMPH, whereas KL-6 levels were within the reference range (mean, 230 U/mL) in all patients. Levels of SP-A and SP-D were significantly higher in subjects with MMPH than those with LAM (p < 0.05).

CONCLUSIONS

Radiographic findings and pulmonary function were stable in all cases of MMPH. Serum SP-A and SP-D, but not KL-6, may be useful markers for suspicion of the presence of MMPH in patients with TSC.

Coexistence of pulmonary lymphangioleiomyomatosis and pulmonary angiomyolipoma

Background

Lymphangioleiomyomatosis (LAM) and angiomyolipoma are two different, but related rare diseases. To the best of our knowledge, pulmonary LAM and pulmonary angiomyolipoma have not previously been observed in the same patient.

Case presentation

A 38-year-old woman presented with a dry cough and left flank pain. She had a right nephrectomy for renal angiomyolipoma 17 years ago. A magnetic resonance imaging scan demonstrated a round mass in the left kidney. A chest computed tomography scan demonstrated scattered small thin-walled cysts and multifocal round nodules in both lungs. A lung biopsy via video-assisted thoracoscopic surgery revealed that the cysts and nodules were manifestations of LAM and angiomyolipomas, respectively. After sirolimus therapy, the renal angiomyolipoma and metastasized pulmonary angiomyolipomas shrank, but pulmonary cysts were unchanged.

Conclusions

LAM and angiomyolipoma are significantly associated, and may coexist in the lungs in rare cases. Sirolimus is effective for both renal angiomyolipoma and metastasized pulmonary angiomyolipomas.

Tuberous sclerosis complex diagnostic criteria update: recommendations of the 2012 Iinternational Tuberous Sclerosis Complex Consensus Conference

BACKGROUND

Tuberous sclerosis complex is highly variable in clinical presentation and findings. Disease manifestations continue to develop over the lifetime of an affected individual. Accurate diagnosis is fundamental to implementation of appropriate medical surveillance and treatment. Although significant advances have been made in the past 15 years in the understanding and treatment of tuberous sclerosis complex, current clinical diagnostic criteria have not been critically evaluated or updated since the last clinical consensus conference in 1998.

METHODS

The 2012 International Tuberous Sclerosis Complex Consensus Group, comprising 79 specialists from 14 countries, was organized into 12 subcommittees, each led by a clinician with advanced expertise in tuberous sclerosis complex and the relevant medical subspecialty. Each subcommittee focused on a specific disease area with important diagnostic implications and was charged with reviewing prevalence and specificity of disease-associated clinical findings and their impact on suspecting and confirming the diagnosis of tuberous sclerosis complex.

RESULTS

Clinical features of tuberous sclerosis complex continue to be a principal means of diagnosis. Key changes compared with 1998 criteria are the new inclusion of genetic testing results and reducing diagnostic classes from three (possible, probable, and definite) to two (possible, definite). Additional minor changes to specific criterion were made for additional clarification and simplification.

CONCLUSIONS

The 2012 International Tuberous Sclerosis Complex Diagnostic Criteria provide current, updated means using best available evidence to establish diagnosis of tuberous sclerosis complex in affected individuals.

Exacerbation and remission of pulmonary micronodules with lymphangioleiomyomatosis around the time of childbirth

We present a case of multifocal micronodular pneumocyte hyperplasia (MMPH), lymphangiomyomatosis (LAM) and angiomyolipoma (AML) in a 33-year-old woman with tuberous sclerosis complex referred to us during her first pregnancy. Computed tomography of the chest showed diffuse micronodules and cysts in both lungs. Compared to those before pregnancy, the number of micronodules increased evidently. We hypothesized the micronodules in both lungs were either LAM, MMPH, or a combination of the two. Bilateral renal AML also intensified. About one month after childbirth, LAM and renal AML decreased without treatment. Therefore, we observed that LAM and AML were affected by the pregnancy. To the best of our knowledge, this is the first case report regarding the reversible alteration of LAM without treatment.

Reversed Halo Sign in Tuberous Sclerosis Complex

We describe a reversed halo sign in a teenage girl with tuberous sclerosis complex (TSC). Lung manifestations of TSC include lung cysts corresponding to lymphangioleiomyomatosis and small nodules indicating multifocal micronodular pneumocyte hyperplasia (MMPH). However, a reversed halo sign in TSC has never been reported. The lesion was microscopically consistent with MMPH. Immunohistological findings also supported the notion that the lesion is associated with TSC.