Rhabdomyoma

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2] Synonyms and keywords: Synonym 1; Synonym 2; Synonym 3

Historical Perspective

• [Disease name] was first discovered by [scientist name], a [nationality + occupation], in [year] during/following [event].
• In [year], [gene] mutations were first identified in the pathogenesis of [disease name].
• In [year], the first [discovery] was developed by [scientist] to treat/diagnose [disease name].

Classification

• Rhabdomyoma may be classified into two types:

• Neoplastic
• Hamartoma

• Neoplastic variety is further classified into three subtypes:

• Adult
• Fetal
• Genital

• Hamartomas are further classified into two subtypes:

• Cardiac rhabdomyoma
• Rhabdomyomatous mesenchymal hamartomas of the skin

Staging

The staging of rhabdomyomas is based on the grade (G), site (T), and metastasis (M), as follows:

• G0 - Benign
• T0 - Intracapsular
• T1 - Extracapsular, intracompartmental
• M0 - None

Stage	Severity	Description
Benign Stage 1	Latent G0T0M0	Remains static or heals spontaneously
Benign Stage 2	Active G0T0M0	Progressive growth but limited by natural barriers
Benign Stage 3	Aggressive G0T1M0	Progressive growth not limited by natural barriers

Pathophysiology

• The pathogenesis of [disease name] is characterized by [feature1], [feature2], and [feature3].
• The [gene name] gene/Mutation in [gene name] has been associated with the development of [disease name], involving the [molecular pathway] pathway.
• On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
• On microscopic histopathological analysis, well-differentiated large cells, which are deeply eosinophilic polygonal with small, peripherally placed nuclei and occasional intracellular vacuoles, which resemble striated muscle cells, are characteristic findings of adult rhabdomyoma.
• On microscopic histopathological analysis, spindle-shaped cells with indistinct cytoplasm and muscle fibres, which resemble striated muscle tissue seen in intrauterine development at 7-12 weeks, are characteristic findings of fetal rhabdomyoma.
• On microscopic histopathological analysis, mixture of fibroblasts cells with clusters of mature cells containing distinct cross-striations and a matrix containing varying amounts of collagen and mucoid material, are characteristic findings of genital rhabdomyoma.
• On microscopic histopathological analysis, cells that closely resemble embryonic cardiac muscle cells, are characteristic findings of cardiac rhabdomyoma.
• On microscopic histopathological analysis, lesions contain poorly oriented or perpendicular bundles of well-differentiated skeletal muscle with islands of fat, fibrous tissue, and occasionally proliferating nerves, are characteristic findings of rhabdomyomatous mesenchymal hamartoma of the skin.

Pathogenesis

Cardiac rhabdomyomas tend to grow up to approximately 32 weeks' gestation, after which point the cells lose their ability to divide and undergo apoptosis. This process is probably mediated by ubiquitin, a regulatory protein that is strongly expressed in rhabdomyoma cells. Ubiquitin stimulates the degradation of myofilaments. Apoptosis ensues and leads to the eventual regression of the hamartoma. Partial or complete resolution occurs in most cases, regardless of the initial size of the tumor. Rhabdomyoma probably represents a genetic variant of striated muscle development. Cardiac rhabdomyoma is considered a hamartomatous proliferation frequently associated with tuberous sclerosis of the brain, sebaceous adenomas, and various hamartomatous lesions of the kidney and other organs. The association of tuberous sclerosis and cardiac rhabdomyoma is important and has usually been explained by strong clinical association.[5] Molecular evidence of this association have now been identified as the TSC2 gene missense mutation (E36; 4672 G>A, 1558 E>K TSC2).[6]

Cardiac rhabdomyomas can occur sporadically, in association with congenital heart malformations, or in the setting of certain genetic disorders.

Causes

• Rhabdomyoma may be caused by either sporadic mutation or in the setting of certain genetic disorders.
• Approximately more than 50% of rhabdomyomas are caused by sporadic mutations. However, in rare cases, Ebstein abnormality, tetralogy of Fallot, and hypoplastic left heart syndrome can be associated with cardiac rhabdomyoma.
• The genetic disorder commonly associated with cardiac rhabdomyoma is tuberous sclerosis.
• The other genetic disorders associated with cardiac rhabdomyomas include basal cell nevus syndrome and Down syndrome in the setting of tuberous sclerosis.
• The familial form of tuberous sclerosis is an autosomal dominant disorder characterized by widespread hamartomas that may involve the kidneys, heart, skin, brain, and other organs.
• Rhabdomyoma is caused by a mutation in the TSC-1 on chromosome 9q34 that encodes for protein hamartin, and TSC-2 on 16p13 that encodes for tuberin. These genes are both tumor suppressor genes that assist in the regulation of growth and differentiation of developing cardiomyocytes.

Differentiating rhabdomyoma from other Diseases

• Rhabdomyomas must be differentiated from other diseases, such as: :*Hibernoma

• Reticulohistiocytoma
• Tuberous sclerosis
• Granular cell tumors

Epidemiology and Demographics

• The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
• In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].

Age

• Adult rhabdomyoma is more commonly observed among patients aged greater than 40 years old.
• Fetal rhabdomyoma is more commonly observed among patients aged between birth and 3 years.
• Cardiac rhabdomyoma is more commonly observed among patients in the pediatric age group.
• Genital rhabdomyoma is more commonly observed among patients in the young and middle-aged women.
• Rhabdomyomatous mesenchymal hamartomas of the skin is more commonly observed among newborns and infants.

Gender

• Cardiac rhabdomyoma affects men and women equally.
• Rhabdomyomatous mesenchymal hamartoma of skin is observed in male and female newborns and infants equally.
• Males are more commonly affected with adult rhabdomyoma than females.
• Males are more commonly affected with fetal rhabdomyoma than females.
• Females are more commonly affected with genital rhabdomyoma than males

Race

• There is no racial predilection for rhabdomyomas.

Risk Factors

• Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].

Natural History, Complications and Prognosis

• The majority of patients with [disease name] remain asymptomatic for [duration/years].
• Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
• If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
• Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
• Prognosis is generally [excellent/good/poor], and the [1/5/10¬year mortality/survival rate] of patients with [disease name] is approximately [#%].

Diagnosis

Diagnostic Criteria

• The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:

• [criterion 1]
• [criterion 2]
• [criterion 3]
• [criterion 4]

Symptoms

• [Disease name] is usually asymptomatic.
• Symptoms of adult rhabdomyoma may include the following:

• Hoarseness
• Difficulty breathing
• Difficulty swallowing

• Symptoms of genital rhabdomyoma may include the following:

• Dyspareunia

• Symptoms of cardiac rhabdomyoma may include the following:

• Shortness of breath

Physical Examination

• Physical examination may be remarkable for:
• The presence of a round or polypoid mass in the region of the neck in adult rhabdomyoma.
• Subcutaneous masses in the head and neck regions in fetal rhabdomyoma.
• Vaginal masses in genital rhabdomyoma
• Cardiac rhabdomyomas may present with heart murmurs. If tuberous sclerosis is associated, the patient displays cerebral palsy–type signs. Renal functions may be altered.

Laboratory Findings

• There are no specific laboratory findings associated with rhabdomyoma.
• The usual laboratory studies that are ordered, includes the following:
  • Complete blood count (CBC)
  • Hemoglobin/hematocrit
  • Platelet count
  • Urinalysis

Imaging Findings

• There are no [imaging study] findings associated with [disease name].
• [Imaging study 1] is the imaging modality of choice for [disease name].
• On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
• [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].

Other Diagnostic Studies

• [Disease name] may also be diagnosed using [diagnostic study name].
• Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].

Treatment

Medical Therapy

• There is no treatment for [disease name]; the mainstay of therapy is supportive care.
• The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
• [Medical therapy 1] acts by [mechanism of action1].
• Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].

Surgery

• Surgery is the mainstay of therapy for [disease name].
• [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
• [Surgical procedure] can only be performed for patients with [disease stage] [disease name].

Prevention

• There are no primary preventive measures available for [disease name].
• Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].

• Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].