Skeletal muscle in the skin is a normal component in several sites. The pathologist who is aware of this regional variation may use it as an aid in determining the site of the skin biopsy in unknown cases and occasionally the sex of the patient. The following table is adopted from the Yus and Simon's paper, cited in the references.Distribution of Striated Muscle Fibers in Facial Skin
If striated muscle fibers are present in the dermis: Site Horizontal fibers in the deep dermis Vellus follicles-Eyelid
Large and abundant sebaceous follicles-Nose except tip
Vertical/oblique fibers in the middle dermis Lips and chin
If striated muscle fibers are not present in the dermis Site Thick subcutis Cheek Thin subcutis With a dense muscular layer beneath subcutis-forehead
Without muscular layer beneath the subcutis-
tip of nose
Sexual Markers in Biopsy Specimens From the Face When Abundant Solar Elastosis is Present
Location Sex Specimen from the cheek With thick terminal hair follicles Male With vellus hair follicles Either male or female Specimen from either the lips or chin With thick terminal hair follicles Male With vellus hair follicles Female
Epidemiology Disease Associations Pathogenesis Laboratory/Radiologic/
Other Diagnostic Testing
Gross Appearance and Clinical Variants Histopathological Features and Variants Special Stains/
Differential Diagnosis Prognosis Treatment Commonly Used Terms Internet Links
CHARACTERIZATION General There are several pathologic conditions where skeletal muscle fibers are present within the dermis. These must be distinguished from normal skin variation VARIANTS MESENCHYMAL HAMARTOMA
J Cutan Pathol. 2006 Apr;33(4):327-30. Abstract quote
A 3-month-old infant girl presented with a polypoid lesion in the perianal region. No changes in this lesion had been noted since birth. Microscopic examination of the excised specimen showed a mixture of mesenchymal elements, dominated by haphazard thin fascicles of skeletal muscle. Collagen and vascular changes were also apparent.
Immunohistochemistry showed positive staining for muscle-specific actin and desmin in the fascicular components of the lesion, and smooth muscle actin, desmin, and h-caldesmon positivity in a haphazard collection of muscle fibers in the deep dermis and anal submucosa. Numerous Verhoeff-van Gieson positive elastic fibers were also noted.
Hamartomas containing skeletal muscle have rarely been reported outside of the head and neck region. They must be distinguished from a variety of other tumors, including juvenile rhabdomyoma, benign Triton tumor, and rhabdomyosarcoma.
J Cutan Pathol. 2002 Apr;29(4):238-43. Abstract quote
BACKGROUND: Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital lesion of the dermis and soft tissues consisting of a disordered and varied collection of mature adipose tissue, skeletal muscle, adnexal elements and nerve bundles. This entity exists under various names including striated muscle hamartoma, congenital midline hamartoma, and hamartoma of cutaneous adnexa and mesenchyme. Several published cases report the occurrence of RMH within the setting of other uncommon congenital abnormalities.
METHODS: We report the clinical and pathologic features of two cases of rhabdomyomatous mesenchymal hamartoma. Patient 1 is a 71-year-old man who presented for removal of a nodule located on his temple that had been traumatized during a recent haircut. Patient 2 is a 4-month-old infant with amnion rupture sequence and rare craniofacial abnormalities including facial clefts, microphthalmia, bilateral colobomas, and a mobile fingerlike projection above the left medial canthus.
RESULTS: Histological examination in both cases showed a deep dermal and subcutaneous fat collection of disorganized skeletal muscle fibers, adipose and neural tissue, and adnexal structures. Characteristically, the skeletal muscle approximated folliculosebaceous structures in a haphazard manner.
CONCLUSIONS: RMH is a rare benign condition of the deep dermis and subcutaneous fat with only 22 cases existing in the English literature. To our knowledge, this is the first report of an elderly man presenting with RMH, presumptively present since birth. There was no evidence of cellular or malignant degeneration. While the etiology of RMH is unknown, possible explanations include aberrancy in the embryonic migration of mesodermally derived tissues or a genetic defect predisposing to the formation of hamartomas.
Rhabdomyomatous mesenchymal hamartoma of skin.
Department of Pathology, Red Cross War Memorial Children's Hospital, Cape Town, South Africa.
Am J Dermatopathol 1989 Feb;11(1):58-63 Abstract quote
A case of a solitary mesenchymal hamartoma occurring on the chin of a newborn infant is presented. The skin nodule exhibited an abnormal arrangement of dermal mesenchymal elements and, in particular, there was prominence of skeletal muscle.
This lesion, which appears to be unique, has been termed rhabdomyomatous mesenchymal hamartoma of skin.
Rhabdomyomatous mesenchymal hamartoma of the eyelid: report of a case and literature review.
Read RW, Burnstine M, Rowland JM, Zamir E, Rao NA.
Doheny Eye Institute, Keck School of Medicine at the University of Southern California, 1450 San Pablo Street, Los Angeles, CA 90033, USA.
Ophthalmology 2001 Apr;108(4):798-804 Abstract quote
PURPOSE: To report a rare case of rhabdomyomatous mesenchymal hamartoma and to compare its features with those cases previously reported.
DESIGN: Interventional case report and literature review.
INTERVENTION: Complete ophthalmologic and systemic examinations followed by excisional biopsy and histopathologic examination.
MAIN OUTCOME MEASURES: Clinical examination features and histopathologic findings.
RESULTS: A 6-month-old Latino male presented with a congenital, elevated, smooth, flesh-colored right lower eyelid lesion. An ipsilateral right limbal dermoid and an upper eyelid coloboma were also present. Excisional biopsy of the eyelid lesion revealed randomly oriented mature striated muscle tissue with associated adipose tissue, blood vessels, pilosebaceous units, and peripheral nerves, findings consistent with rhabdomyomatous mesenchymal hamartoma. Of the 24 reported cases (including the current case), eight had associated congenital anomalies.
CONCLUSIONS: Although rhabdomyomatous mesenchymal hamartomas are rare and benign, they may be associated with other congenital anomalies and anomaly syndromes. As a result, we recommend systemic evaluation of patients diagnosed with this entity.
Am J Dermatopathol 1990;12:485-491
Acta Derm Venereol 1998;78:390
Proposed name of Hamartoma of cutaneous adnexa and mesenchyme since this does not emphasize skeletal muscle which is a component of the mesenchyme
STRIATED MUSCLE HAMARTOMA Pediatr Dermatol 1986;3:153-157
Two newborn infants with soft fibroma-like lesions, one on the sternal notch and the other on the upper lip
Striated muscle fibers in the central core and periphery, below the epidermis
J Cutan Pathol 1994;21:40-46
Possible relationship to Delleman's syndrome
Am J Dermatopathol 2001;22:503-509.
Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
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. Fourth Edition. Mosby 2001.
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