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Although rare, benign tumors of skeletal and cardiac muscle can occur. In the heart, they may be associated with the syndrome of tuberous sclerosis in 50-86% of cases. These tumors are often considered hamartomas, similar to other tumors arising in tuberous sclerosis. In the soft tissue, these tumors are most common in the head and neck area and are probably true neoplasms. Occasionally, these tumors may present as a mass in the extremity. Overall, they are solitary in 80% and multiple in 20%. They are usually asymptomatic by may produce symptoms such as dysphagia, hoarseness, and odynophagia, when occurring in the oropharynx.


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AGE RANGE-MEDIAN Majority over 40 years but any age has been reported
5 weeks-85 years
Mean 65 years
Men favored 6:1


Cardiac tumors Often considered hamartomas
Extracardiac tumors of the head and neck A clonal balanced translocation has been found in chromosomes 15 and 17


Cardiac May present with dysrhythmias or heart block

Least common variant
Most common in the head and neck region

Genital Usually vagina or vulva of middle aged women

Epididymal rhabdomyoma: report of a case, including histologic and immunohistochemical findings.

Wehner MS, Humphreys JL, Sharkey FE.

Department of Pathology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78284-7750, USA.

Arch Pathol Lab Med 2000 Oct;124(10):1518-9 Abstract quote

Genital rhabdomyoma is a rare tumor of skeletal muscle origin that is usually found in the vulvar area of young women. The English literature contains only 2 previous case reports involving men, both of whom were 19 years old. One of these lesions originated in the tunica vaginalis of the testis, and the other originated in the prostate gland.

We present the clinical, histologic, and immunohistochemical findings of an epididymal rhabdomyoma in a 20-year-old man. To our knowledge, this is the first such case reported in this location.

Cutaneous Fetal Rhabdomyoma: A Case Report and Historical Review of the Literature.

*Department of Pathology and Immunology, Division of Surgical Pathology, Washington University/Barnes-Jewish Hospital †Cutaneous Pathology, WPC Laboratories, Inc, St Louis, MO.


Am J Surg Pathol. 2008 March 32(3);485-491 Abstract quot

Fetal rhabdomyomas are well-documented tumors, affecting both children and adults that are composed of immature striated muscle at the sixth to tenth-week stage of development. Although there is often a predilection for the head and neck region, these tumors have been identified in a wide array of anatomic sites. A primary cutaneous presentation, however, has not yet been described.

We report the first case of a fetal rhabdomyoma arising in the skin of a 1-year old girl. After the initial biopsy, an incomplete excision was performed with tumor present histologically at multiple surgical margins. In a follow-up period of 54 months, there has been no lesional regrowth or evidence of further progression.

This case is detailed, in addition to a literature-based review of the historical and conceptual development of the neoplasm known as fetal rhabdomyoma.


General Large polygonal cells with well defined striated muscle cytoplasm

Adult cellular rhabdomyoma of the heart: a report of 3 cases.

Burke AP, Gatto-Weis C, Griego JE, Ellington KS, Virmani R.

Department of Cardiovascular Pathology, Armed Forces Institute of Pathology, Washington DC 20306-6000, USA.

Hum Pathol 2002 Nov;33(11):1092-7 Abstract quote

We present 3 adults with cardiac rhabdomyomas, 2 in the atria and 1 in the right ventricle. One atrial tumor was discovered incidentally, and 1 resulted in supraventricular tachycardia. The ventricular lesion caused ventricular tachycardia.

Compared with congenital rhabdomyomas, the tumors are relatively cellular, the cells are smaller, there are few spider cells, and there is evidence of cell proliferation. Two of the 3 tumors demonstrated spindling in contrast to adult rhabdomyomas of the head and neck.

Although surgical excision was possible in all patients, long-term follow-up will be required to determine the true biologic behavior of these neoplasms.



Positive Vimentin
Muscle specific actin

Fetal rhabdomyoma of the head and neck: a clinicopathologic and immunophenotypic study of 24 cases.

Kapadia SB, Meis JM, Frisman DM, Ellis GL, Heffner DK.

Department of Otolaryngic and Endocrine Pathology, Armed Forces Institute of Pathology, Washington, DC.

Hum Pathol 1993 Jul;24(7):754-65 Abstract quote

Twenty-four fetal rhabdomyomas (FRMs) of the head and neck occurring in 16 male and seven female patients (sex unknown in one), ranging from 3 days to 58 years of age (median, 4.5 years) are reported.

Ten patients (42%) were < or = 1 year old, six lesions (25%) were congenital, and 11 lesions (46%) occurred in patients > or = 15 years of age. The median tumor size was 3.0 cm (range, 1.0 to 12.5 cm). The FRMs presented as well-defined, solitary masses arising within the soft tissue or mucosa (2:1) of the head and neck. The median follow-up in 15 cases was 48 months (range, 2 months to 52 years) after diagnosis.

With the exception of one patient with a local recurrence, all patients were either alive and well or dead of unrelated causes. Eight cases, regarded as "classic" FRM, consisted predominantly of bland, primitive spindled cells associated with delicate, elongated skeletal muscle cells reminiscent of fetal myotubules that were haphazardly arranged in an abundant fibromyxoid stroma. The remaining 16 cases, designated as "intermediate" FRM, displayed both a greater degree and a greater number of cells with skeletal muscle differentiation as well as a variety of distinctive cytologic and architectural features. These included the presence of large, ganglion cell-like rhabdomyoblasts with vesicular nuclei and prominent nucleoli, interlacing ribbon or strap-like rhabdomyoblasts with deeply acidophilic cytoplasm, broad bundles of more delicate spindled rhabdomyoblasts arranged in fascicles simulating smooth muscle, an occasional plexiform pattern with infiltration of adipose tissue and skeletal muscle, focal intimate association with peripheral nerves, and rare areas of fibroblastic proliferation. Mitoses were not found in 19 of the 24 FRM cases, but in five tumors there were 1 to 14 mitoses/50 high-power fields. Marked nuclear atypia, anaplasia, and a "cambium layer" were uniformly absent.

The FRMs typically stained for myoglobin, desmin, and muscle-specific actin with focal or rare staining for vimentin, smooth muscle actin, S-100 protein, glial fibrillary acidic protein, and Leu-7. Cytokeratin, epithelial membrane antigen, and CD68 antigen (with KP1) were not detected.

This study expands on previous reports of FRM and demonstrates that it has both a broader age range and histologic spectrum than previously recognized. The mitotic rates of FRM as well as certain histologic features overlap with rhabdomyosarcoma; the lack of marked nuclear atypia is an important distinguishing feature.



Hamartoma of mature cardiac myocytes.

Burke AP, Ribe JK, Bajaj AK, Edwards WD, Farb A, Virmani R.

Department of Cardiovascular Pathology, Armed Forces Institute of Pathology, Washington, DC 20306-6000, USA.

Hum Pathol 1998 Sep;29(9):904-9 Abstract quote

The clinical and pathological findings of three patients with hamartomas of mature cardiac myocytes resembling localized hypertrophic cardiomyopathy are presented. Hypertrophic cardiomyopathy is manifest by a poorly demarcated area of cardiac hypertrophy, microscopically demonstrating myofiber disarray and intramural coronary thickening.

Localized, nonencapsulated masses of hypertrophied cardiac myocytes in locations other than the left ventricle or ventricular septum have not been reported. The clinical and pathological data of three patients with localized hamartomas were retrospectively retrieved. The patients were 9, 22, and 28 years old, respectively; none had a known family history of heart disease or cardiomyopathy. Two patients had cardiac arrhythmias: one patient died suddenly, and one patient had the Wolff-Parkinson-White syndrome. The third patient was asymptomatic. Two patients treated surgically had single masses in the right atrium and right ventricle, respectively. The patient who died suddenly had multiple discrete masses throughout the atrial and ventricular myocardium, including the left ventricular free wall. None of the three patients had septal asymmetry suggestive of hypertrophic cardiomyopathy.

Histologically, there were discrete but unencapsulated nodules of marked myocyte hypertrophy with disorganization, focal scarring, and thickened intramural arteries. There was no myocyte vacuolization suggestive of cardiac rhabdomyoma.

Ultrastructurally, the myocytes showed abundant and disorganized myofilaments and normal intercellular junctions.

Hamartoma of mature cardiac myocytes is a previously undescribed cardiac tumor that shares some features of hypertrophic cardiomyopathy and rhabdomyoma, but is currently best considered a separate entity.

Hamartoma of mature cardiac myocytes: a case report.

Sturtz CL, Abt AB, Leuenberger UA, Damiano R.

Department of Pathology, The Milton S. Hershey Medical Center, Penn State Geisinger Health System, Hershey, Pennsylvania 17033, USA

Mod Pathol 1998 May;11(5):496-9 Abstract quote

A 24-year-old man presented with hypertension, palpitations, and premature atrial and ventricular contractions. A mass was discovered in the distal interventricular septum that was composed of dense collagenous tissue, fat, and disorganized, hypertrophic, mature cardiac myocytes indicative of a cardiac hamartoma.

This entity has only rarely been reported and must be distinguished from the much more common rhabdomyoma and from oncocytic cardiomyopathy, which is also referred to as "cardiac hamartoma."

Rhabdomyomatous mesenchymal hamartoma associated with nasofrontal meningocele and dermoid cyst.

Takeyama J, Hayashi T, Sanada T, Shimanuki Y, Saito M, Shirane R.

Department of Pathology, Miyagi Children's Hospital, Sendai, Japan.
J Cutan Pathol. 2005 Apr;32(4):310-3. Abstract quote  

A 1-year-6-month-old girl presented with a subcutaneous tumor of the forehead, which had developed since birth. The preoperative examinations showed nasofrontal bone defect with meningocele and subcutaneous tumor with cyst. The patient underwent excision of the tumor and reconstruction of the bone defect.

Histologically, the skin tumor exhibited disordered arrangement of striated muscle fibers among normal dermal components, and the cyst was lined by cornified epithelium with a few hair adnexa and contained lamellated keratin. These findings were consistent with rhabdomyomatous mesenchymal hamartoma (RMH) and dermoid cyst. This is an interesting case of RMH co-existing with nasofrontal meningocele and dermoid cyst in the same area.

We suggest embryologic errors as a possible etiology, which is incomplete dysjunction of the neural ectoderm from the cutaneous ectoderm. Failure of insertion of mesoderm between the ectoderms caused the bone defect and the disordered proliferation and differentiation of mesoderm-derived tissue, leading to formation of hamartoma.


Recurrence 8/19 (42%) for head and neck tumors over a 2-11 year time period
Metastasis None
Treatment Simple excision

Macpherson and Pincus. Clinical Diagnosis and Management by Laboratory Methods. Twentyfirst Edition. WB Saunders. 2006.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 6th Edition. McGraw-Hill. 2003.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fifth Edition. Mosby Elesevier 2008

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Strap or Spider cells-Characteristic histologic change of immature skeletal muscle cells.

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Last Updated March 10, 2008

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