AAD BF Cutaneous Smooth Muscle Tumors

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Cutaneous smooth muscle tumors

by Hayder A. Asfoor, MD
Smooth muscle hamartoma

• Congenital (most common) or acquired
• Clinically:
o Firm, hyperpigmented or skin-colored plaque + hypertrichosis or follicular papules
o Diffuse cutaneous smooth muscle hamartomas may result in the Michelin-Tire Baby
phenotype.
• May be associated and overlap with Becker’s nevus clinically and on histopathology.
However, smooth muscle hamartomas classically differ from Becker’s nevus by earlier
onset (at birth vs second decade) and location (trunk and extremities vs shoulder or
chest).
• May be pseudo-Darier’s sign positive (stroking the lesions cause induration and erythema
due to SM contraction).
• Histology→ Haphazardly arranged SM bundles in the dermis with epidermal acanthosis
and basal layer hyperpigmentation.
• IHC→ positive for SMA, desmin, and smoothelin
• Tx: May perform excision for cosmetic reasons (no malignancy potential)
Leiomyoma
• Benign mesenchymal neoplasms with SM differentiation
• Three Types:
1. Pilar Leiomyoma • Two Types:
o Multiple: younger age of onset affecting the trunk
(arrector pili
origin) and limbs equally. a/w Reed’s syndrome (+ uterine
leiomyoma and RCC)
o Solitary: typically in adults, with affinity for the limbs.
• Clinically→ firm, reddish-brown or skin colored nodules,
papulonodules, or plaques; typically painful, especially with
cold exposure
• May be pseudo-Darier’s sign positive
• Histology→ circumscribed proliferations of interlacing
bundles of SM fibers within the reticular dermis
• IHC→ positive for SMA and desmin. Calponin and
h-caldesmon are also supportive
• Tx:
Hayder A. o Solitary: complete surgical excision
Asfoor, MD, is o Multiple: nifedipine, nitroglycerin, phenoxybenza-
a fellow of the Arab
mine, gabapentin and hyoscine hydrobromide for
Board of Health
Specializations, pain, CO2 laser
CABDV, and has
specialty certification
in dermatology 2. Genital • Clinically→ similar to pilar type but usually larger; typically
from Royal College Leiomyoma solitary and painless
of Physicians, UK,
department of (Dartoic, vulvar • Involving vulva, scrotum, penis, nipple, or areola
medicine - Kerbala or mammary • Histology→ more circumscribed appearance than pilar
College of Medicine. sm origin) leiomyomas and may have mitoses
• IHC and Rx: same as pilar leiomyoma
p. 4 • Fall 2020 www.aad.org/DIR

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Cutaneous smooth muscle tumors Bonus
by Hayder A. Asfoor, MD
Boards!
Leiomyoma (cont.)
3. Angioleiomyoma • Pericytic tumor (Myoid differentiation)
• Clinically→ solitary nodule in the lower extremities; often
(perivascular SM painful
origin) • Histology→ well circumscribed proliferation of fascicles of
spindled SM cells admixed with blood vessels within SC. In addition to this
issue’s Boards Fodder,
Three variants: solid, venous, and cavernous.
you can download
• IHC→ positive for MSA, SMA, and calponin. Variable for another new online
desmin and h-caldesmon. Boards Fodder chart.
• Tx: Simple surgical excision
Neuromodulators
by Stefanie Altmann,
Leiomyosarcoma DO, is now available
• Rare: ~4% of cutaneous soft tissue sarcomas. to download at
www.aad.org/
• Two types:
Directions.
o Dermal leiomyosarcoma: arises from arrector pili or genital sm with indolent
clinical behavior
o Subcutaneous leiomyosarcoma: arises from vascular sm with aggressive behavior The AAD now has
and risk of metastasis in up to 40% more than 100 Boards
• Clinically→ solitary red brown and painful nodule, involving extremities, trunk, and head Fodder study charts!
Check out
and neck region of elderly the archives at
• Histology→ diffusely infiltrative or well-demarcated nodular pattern with SM differentiation www.aad.org/
+ variable degrees of atypia boardsfodder.
• IHC→ positive for MSA, SMA. Variable for desmin (though classically +), h-caldesmon,
keratin and S100.
• Tx: WLE
Abbreviations:
• IHC: immunohistochemistry
• SMA: smooth muscle actin
• MSA: muscle specific actin Got Boards?
• a/w: associated with
• RCC: renal cell carcinoma
• SM: smooth muscle
• SC: subcutis
• Tx: treatment
• WLE: wide local excision
Directions in
References: Residency is currently
1. Bolognia J, Jorizzo J, Schaffer I. Dermatology. Philadelphia: Elsevier; 2018. accepting
submissions for new
2. Rapini RP. Practical dermatopathology. Elsevier Health Sciences; 2012 Aug 23.
Boards Fodder charts
3. Alikhan A, Hocker TL. Review of Dermatology E-Book. Elsevier Health Sciences; 2016 Oct 22. for 2020-2021. Get
4. Lau, Sean K., and Stephen S. Koh. “Cutaneous Smooth Muscle Tumors: A Review.” Adv Anat published, impress
Pathol. 2018;25(4): 282-290. your friends,
5. Aneiros-Fernandez J, Antonio Retamero J, Husein-Elahmed H, et al. Primary cutaneous and and help out your
subcutaneous leiomyosarcomas: evolution and prognostic factors. Eur J Dermatol. 2016;26: fellow residents.
Contact Dean Monti,
9–12.
dmonti@aad.org with
6. Espiñeira-Carmona, María Jose, et al. “Smoothelin, a new marker for smooth muscle hamar- your chart ideas.
toma.” Eur J Dermatol. 2012;22:549-550.
A Publication of the American Academy of Dermatology | Association Fall 2020 • p. 5

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boards fodder

Cutaneous smooth muscle tumors

Smooth muscle hamartoma

p. 4 • Fall 2020 www.aad.org/DIR

A Publication of the American Academy of Dermatology | Association Fall 2020 • p. 5

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