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dermatofibroma (benign fibrous histiocytoma)
Common, benign, button-like dermal nodule generally occurring on the extremities.
Etiology:
- minor injury
- insect bites
- shaving injury
- folliculitis
- idiopathic
Epidemiology:
1) occurs in adults
2) females > males
Pathology:
1) whorling fascicles of spindle cells
a) small amounts of pale blue cytoplasm
b) elongated nuclei
2) variable increase in vascular spaces
3) overlying epidermis is frequently hyperplastic
* histopathology images [4]
Clinical manifestations:
1) papule or nodule 3-10 mm in diameter
- about the size of a pencil eraser [2]
- image in MKSAP18 [2] looks like a nipple
2) may be domed or depressed below surface of surrounding skin
3) borders ill-defined
4) texture may be dull, shiny or scaly
5) color variable: pink, tan, brown, dark brown, but generally darker at center, fading towards edges
6) post-inflammatory hyper or hypopigmentation at center may occur secondary to repeated trauma
7) firm papule or nodule
8) dimple sign: lateral compression with thumb & index finger produces a depression or "dimple"
9) distribution:
a) legs > arms > trunk
b) uncommon on head, palms, soles
c) may be multiple, randomly scattered
10) lesions appear gradually over several months
11) lesions may persist for years without increase in size
12) lesions may regress spontaneously
* images [3,4]
Laboratory:
- skin biopsy not necessary [2]
Differential diagnosis:
1) malignant melanoma
2) scar
3) blue nevus
4) pilar cyst
5) metastatic carcinoma
6) Kaposi's sarcoma
7) dermatofibrosarcoma protuberans
Management:
1) surgical excision
a) generally not indicated
b) resultant scar may be less acceptable than dermatofibroma
c) indications:
1] repeated trauma
2] cosmetic disfigurement
3] uncertainty in diagnosis
2) cryotherapy with liquid nitrogen
Related
blue nevus (dermal melanocytoma)
cicatrix (scar)
dermatofibrosarcoma protuberans
Kaposi's sarcoma
malignant fibrous histiocytoma (MFH, angiomatoid fibrous histiocytoma)
melanoma
trichilemmal cyst (pilar cyst, isthmus catagen cyst)
General
histiocytoma
skin neoplasm
References
- Color Atlas and Synopsis of Clinical Dermatology, Common
and Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY,
1997, pg 172-73
- Medical Knowledge Self Assessment Program (MKSAP) 16, 17, 18.
American College of Physicians, Philadelphia 2012, 2015, 2018.
- DermNet NZ. Dermatofibroma (images)
http://www.dermnetnz.org/lesions/dermatofibroma.html
- Pierson JC, Elston DM
Medscape: Dermatofibroma
http://emedicine.medscape.com/article/1056742-overview