Hamartoma of Mature Cardiac Myocytes: Case Report and Review of the Literature

Hamartoma of Mature Cardiac Myocytes presenting as a polypoid epicardial tumor in the interatrial groove and with gene fusions by copy number anomalies of chromosome 7

Hamartoma of Mature Cardiac Myocytes (HMCM) is an extremely rare cardiac tumor characterized by benign growth of differentiated mature striated cardiac myocytes, and usually involves the ventricular myocardium. We describe the case of a 15-year-old female who presented with a short history of atrial fibrillation and a polypoid epicardial tumor that was attached to the interatrial groove by a short pedicle. The resected specimen showed features consistent with HMCM. Although these tumors are not associated with any known molecular or cytogenetic abnormalities, we identified fusions transcripts along with complex copy number anomalies of chromosome 7.

Hamartoma of Mature Cardiac Myocytes: Systematic Review

BACKGROUND

While primary cardiac tumors are rare, it has been increasingly recognized due to improvement in screening measures. However, the hamartoma of mature cardiac myocytes has been underrecognized compared to other cardiac tumors, such as cardiac myxomas and papillary fibroelastomas, and is still potentially associated with critical consequences such as sudden death. This systematic review aims to summarize the evidence regarding the hamartoma of mature cardiac myocytes and characterize the presentations and symptoms for clinicians.

METHODS

Following the PRISMA statement, we searched MEDLINE and EMBASE for all peer-reviewed articles using keywords including "hamartoma of mature cardiac myocytes" from their inception to January 2nd, 2023.

RESULTS

We included 25 articles, including 34 cases, in this systematic review. Patients with hamartoma of mature cardiac myocytes commonly presented with nonspecific symptoms such as dyspnea (35.3%), although a few presented with sudden death and syncope. The left ventricle was the common site of origin (41.2%), followed by the right atrium and ventricle. Surgery was commonly pursued for diagnosis and treatment, while a few required cardiac transplants (8.8%), and 29.4% were diagnosed with autopsy or expired.

CONCLUSION

Hamartoma of mature cardiac myocytes is a potentially underrecognized primary cardiac tumor associated with treatable yet potentially critical consequences. Given the challenges of differentiating it from malignancy such as angiosarcoma, multimodal imaging needs to be utilized to pursue a diagnosis. Future studies are warranted to develop a noninvasive diagnosis mode for cardiac tumor.

A left atrial hamartoma of mature cardiac myocytes

We present a case of a hamartoma of mature cardiac myocytes. This is an extremely rare tumour and the first reported paediatric case localised in the left atrium.

Primary and secondary cardiac tumors: clinical presentation, diagnosis, surgical treatment, and results

Cardiac tumours are some of the rarest primary tumours, while cardiac metastasis are more common yet still relatively rare. Seventy five percent of primary cardiac tumours are benign tumours. Cardiac tumours present with a range of obstructive, embolic, arrhythmic or systemic symptoms, and in many cases may present asymptomatically. The clinical presentation depends largely on the size and location of the mass. With advances in cardiac imagining and the introduction of cardiopulmonary bypass, the diagnosis and surgical treatment of these rare tumours has improved the prognosis and outlook for benign and malignant tumours. Management depends on tumour histology, size and location as well as the clinical presentation. Conservative management is reserved for small, benign tumours that can undergo regular echocardiographic follow-up. Symptomatic benign tumours are treated with surgical resection and the results are excellent. Malignant primary cardiac tumours have a poor prognosis with high rates of relapse and a median survival of 10-24 months.

Atypical Presentation of Right Ventricular Cardiac Hamartoma in a Young Man

Cardiac tumors in adults are exceedingly rare and usually benign. We describe a 29-year-old man with a previous diagnosis of interventricular septal hypertrophy who presented with increasing severity of dyspnea and fatigue. Work-up revealed a 4.9 × 3.7 cm mass at the base of the interventricular septum. Biopsy revealed a benign cardiac hamartoma atypically located in the right ventricle, and the mass was resected via right ventriculotomy.

A Rare Case of Cardiac Mesenchymal Hamartoma and Comprehensive Review of the Literature With Emphasis on Histopathology

Hamartomas are primary, benign neoplastic lesions that most commonly derive from a single variably differentiated cell lineage. Here, we report an unusual case of a cardiac hamartoma. A 62-year-old woman presented with chest pain and palpitations. Serial imaging revealed a large slowly growing and highly vascularized left ventricular mass, which required surgical resection. Microscopically, the lesion was composed of nodular fibrovascular proliferation with haphazardly embedded muscle bundles and peripheral calcifications. Immunohistochemical studies revealed prominent muscle-specific actin positive and smooth muscle actin positive muscle fiber bundles within a disorganized fibrovascular stroma. This characterization is most consistent with cardiac mesenchymal hamartoma. Relevant differential diagnoses for this lesion include hamartoma of mature cardiac myocytes (HMCMs) and intramuscular hemangioma. The prominent smooth muscle differentiation of muscle bundles was incompatible with defining features of HMCM. Absence of S100-positive nerve and mature adipose cells distinguished this lesion from the recently defined, heterogeneous cardiac mesenchymal hamartoma. Forty-seven cases of cardiac hamartoma reported from 1970 to 2020 were reviewed to provide histopathologic context.

Defined factors to reactivate cell cycle activity in adult mouse cardiomyocytes

Adult mammalian cardiomyocytes exit the cell cycle during the neonatal period, commensurate with the loss of regenerative capacity in adult mammalian hearts. We established conditions for long-term culture of adult mouse cardiomyocytes that are genetically labeled with fluorescence. This technique permits reliable analyses of proliferation of pre-existing cardiomyocytes without complications from cardiomyocyte marker expression loss due to dedifferentiation or significant contribution from cardiac progenitor cell expansion and differentiation in culture. Using this system, we took a candidate gene approach to screen for fetal-specific proliferative gene programs that can induce proliferation of adult mouse cardiomyocytes. Using pooled gene delivery and subtractive gene elimination, we identified a novel functional interaction between E2f Transcription Factor 2 (E2f2) and Brain Expressed X-Linked (Bex)/Transcription elongation factor A-like (Tceal) superfamily members Bex1 and Tceal8. Specifically, Bex1 and Tceal8 both preserved cell viability during E2f2-induced cell cycle re-entry. Although Tceal8 inhibited E2f2-induced S-phase re-entry, Bex1 facilitated DNA synthesis while inhibiting cell death. In sum, our study provides a valuable method for adult cardiomyocyte proliferation research and suggests that Bex family proteins may function in modulating cell proliferation and death decisions during cardiomyocyte development and maturation.

Hamartoma of mature cardiomyocytes in right atrium: A case report and literature review

RATIONALE

Tumors in the heart are rare. Myxomas, rhabdomyomas, and fibromas are the most common benign cardiac tumors. Hamartoma of mature cardiomyocytes (HMCM) is another benign cardiac tumor, are very rare and have only been reported in a few literatures.

PATIENT CONCERNS

We report a case of 41-year-old male who suffered short of breath for 3 years, and lower limbs edema for 2 years.

DIAGNOSES

Transthoracic echocardiogram (TTE) and cardiac magnetic resonance (CMR) showed a large amount of pericardial effusion and confirmed a mass of 18 × 14 mm on the superior vena cava near the outer edge of right atrium. The patient was first diagnosed as pleural mesothelioma. Surgery was performed to relieve the symptoms and confirm diagnoses. However, during surgery, we found the right atrium is apparently thicken with rough and uneven surface. Histology of right atrium mass indicated it as hamartoma of mature cardiomyocytes.

INTERVENTION

We resected the thicken atrial wall completely, reconstructed right atrium with bovine pericardial patch, and resected the pericardium.

OUTCOMES

Patient was discharged 9 days after surgery, and remained asymptomatic during 9 months follow up.

LESSONS

Hamartoma of mature cardomyocytes is a rare benign cardiac tumor. There were 26 cases reported until now. The conclusive diagnosis depends on pathological sections. For patients with symptoms, surgery is an effective treatment for HMCM.

An unusual tumour: Hamartoma of mature cardiac myocytes

Heart neoplasms are uncommon and usually benign. Hamartoma of mature cardiac myocytes is an unusual lesion with only a few reported cases. It is a heterogeneous mixture of well-differentiated myocytes, fibroblasts, adipocytes and blood vessels. We present a case of hamartoma of mature cardiac myocytes and a concise review of the pertinent literature. A multi-lobulated polypoid tumour attached to the wall of the right atrium was found during an autopsy of a young woman. Microscopy revealed cardiomyocytes, fibrous connective tissue and well-differentiated adipocytes. The immunohistochemical study had a positive immunoreactivity for desmin, muscle-specific actin (HHF-35) and CD34 markers, showing the different types of mesenchymal cells involved. This combination of markers has not been previously used. Other tumours, such as cardiac rhabdomyoma and cardiac myxoma were ruled out due to the differences in histological characteristics and clinical presentation.

Hamartomas and other tumor-like malformations of the lungs and heart

Tumor-like malformative lesions are seen throughout the body, and they may be confused with true neoplasms by clinicians and pathologists alike. In the lungs, they are principally represented by hamartomas-which may contain chondroid, adipocytic, fibroblastic, and myxoid tissue, with entrapped bronchiolar epithelium-and congenital pulmonary airway malformations (CPAMs). The latter have been subdivided into 5 groups, based on their histological features, but they basically comprise proliferations of malformed bronchopulmonary tissues of different types. Type 1 lesions have a capacity for malignant transformation in a small proportion of cases. Malformative cardiac tumefactions include rhabdomyoma-like hamartomas; fibromatous hamartomas; and mesenchymal ventricular hamartomas, which contain cardiac muscle, smooth muscle, fat, vasogenic tissue, and nerves. Another intracardiac proliferation in the same general category is seen in the interatrial septum, in the region of the atrioventricular node. It comprises randomly-disposed gland-like profiles that are made up of endodermal epithelium. Originally thought to be a form of mesothelial lesion, that abnormality is now classified as an endodermal choristoma. All forms of pulmonary and cardiac malformations are only rarely symptomatic, and the necessity for surgical excision of them depends on the particular details of each case.

Cardiac Hamartoma: A Diagnostic Challenge

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Cardiac hamartoma is a rare clinical entity with hypertrophied myocytes mixed with fibro-vascular and fatty tissues.

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Multi-modality imaging is needed to narrow the differential diagnosis.

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Surgical resection can lead to the definitive diagnosis in some cases.

Developmental alterations in centrosome integrity contribute to the post-mitotic state of mammalian cardiomyocytes

Mammalian cardiomyocytes become post-mitotic shortly after birth. Understanding how this occurs is highly relevant to cardiac regenerative therapy. Yet, how cardiomyocytes achieve and maintain a post-mitotic state is unknown. Here, we show that cardiomyocyte centrosome integrity is lost shortly after birth. This is coupled with relocalization of various centrosome proteins to the nuclear envelope. Consequently, postnatal cardiomyocytes are unable to undergo ciliogenesis and the nuclear envelope adopts the function as cellular microtubule organizing center. Loss of centrosome integrity is associated with, and can promote, cardiomyocyte G0/G1 cell cycle arrest suggesting that centrosome disassembly is developmentally utilized to achieve the post-mitotic state in mammalian cardiomyocytes. Adult cardiomyocytes of zebrafish and newt, which are able to proliferate, maintain centrosome integrity. Collectively, our data provide a novel mechanism underlying the post-mitotic state of mammalian cardiomyocytes as well as a potential explanation for why zebrafish and newts, but not mammals, can regenerate their heart.

DOI:http://dx.doi.org/10.7554/eLife.05563.001

Muscle cells in the heart contract in regular rhythms to pump blood around the body. In humans, rats and other mammals, the vast majority of heart muscle cells lose the ability to divide shortly after birth. Therefore, the heart is unable to replace cells that are lost over the life of the individual, for example, during a heart attack. If too many of these cells are lost, the heart will be unable to pump effectively, which can lead to heart failure. Currently, the only treatment option in humans with heart failure is to perform a heart transplant.

Some animals, such as newts and zebrafish, are able to replace lost heart muscle cells throughout their lifetimes. Thus, these species are able to fully regenerate their hearts even after 20% has been removed. This suggests that it might be possible to manipulate human heart muscle cells to make them divide and regenerate the heart. Recent research has suggested that structures called centrosomes, known to be required to separate copies of the DNA during cell division, are used as a hub to integrate the initial signals that determine whether a cell should divide or not.

Here, Zebrowski et al. studied the centrosomes of heart muscle cells in rats, newts and zebrafish. The experiments show that the centrosomes in rat heart muscle cells are dissembled shortly after birth. Centrosomes are made of several proteins and, in the rat cells, these proteins moved to the membrane that surrounded the nucleus. On the other hand, the centrosomes in the heart muscle cells of the adult newts and zebrafish remained intact.

Further experiments found that that breaking apart the centrosomes of heart muscle cells taken from newborn rats stops these cells from dividing. Zebrowski et al.'s findings suggest that the loss of centrosomes after birth is a possible reason why the hearts of adult humans and other mammals are unable to regenerate after injury. In the future, these findings may aid the development of methods to regenerate human heart muscle and new treatments that may limit division of cancer cells.

DOI:http://dx.doi.org/10.7554/eLife.05563.002