Chapter 43 Fibrous tumors of the skin
1. What are tumors of fibrous tissue?
Tumors of fibrous tissue are mesenchymal tumors composed of fibroblasts or their variants. Fibroblasts produce normal structural components of the dermis, including collagen, elastin, and ground substance (dermal mucin). Most tumors of fibroblast origin produce collagen, but they may also produce dermal mucin or elastin as the primary product. Some tumors are composed primarily of myofibroblasts, specialized fibroblasts that demonstrate contractile properties because of cytoplasmic actin filaments. Other specialized fibroblasts may demonstrate phagocytosis, and tumors demonstrating this characteristic are referred to as fibrohistiocytic tumors. Tumors of fibrous tissue are conventionally divided into those that are fibrous and those that are fibrohistiocytic (Table 43-1).
2. What is an acrochordon?
An acrochordon (skin tag, fibroma durum) is a soft, flesh-colored to dark brown, often pedunculated, cutaneous papule usually located on the neck, axilla, or groin (Fig. 43-1A). It is probably the most common mesenchymal neoplasm. Acrochordons are often multiple, usually 1 to 4 mm in size, but occasionally 3 cm or larger in diameter. The larger baglike lesions often also contain some fat and are called soft fibromas or fibroepithelial polyps (Fig. 43-1B).
3. Is there a known cause for acrochordons?
An exact cause is not known. The frequent association of acrochordons with diabetes mellitus, obesity, pregnancy, menopause, acanthosis nigricans (see Fig. 43-1A), and certain endocrinopathies suggests that they are hormonally induced. However, the ubiquitous nature of these lesions in healthy older adults has been interpreted by some authorities as simply a manifestation of skin aging.
Demir S, Demir Y: Acrochordon and impaired carbohydrate metabolism, Acta Diabetol 39:57–59, 2002.
4. Are any complications associated with acrochordons?
Yes. The most common complications are recurrent trauma to individual lesions (e.g., laceration with a shaving razor) or spontaneous torsion and infarction of a pedunculated lesion. When a pedunculated lesion twists on its stalk, the blood supply is compromised and tissue ischemia occurs. Usually, sudden pain, swelling, necrosis, and even secondary infection result. Often, this sequence of events results in disappearance of the lesion.
5. Are acrochordons associated with intestinal polyposis?
Several widely reported studies asserted a statistically significant association between the presence of acrochordons and colonic polyps. However, other investigators, using methodology that better accounted for the fact that 60% to 70% of the elderly have acrochordons, demonstrated no statistical association. Most dermatologists believe that acrochordons are not a marker for colonic polyps but are simply more common in the elderly population, which is predisposed to colonic polyposis.
6. How can acrochordons be treated?
The simplest way to treat acrochordons is scissors-snip excision (usually without anesthesia). Smaller lesions can be rapidly treated by electrodesiccation or even cryotherapy (beware of postinflammatory dyspigmentation with cryotherapy). Larger lesions (>2 cm) can be shaved off after local anesthesia or excised.
7. What is a hypertrophic scar?
A hypertrophic scar represents excessive collagen deposition at a site of wound healing. Typically, the scars are initially red, raised, firm, and often pruritic. With time, they flatten and become white. Hypertrophic scars do not extend beyond the limits of the original trauma. Scars, including hypertrophic scars, are not usually considered to be neoplasms because they are reactive and eventually regress with time.
8. What is a keloid?
A keloid also represents excessive collagen deposition at a site of wound healing. Clinically, a keloid can be indistinguishable from a hypertrophic scar, though the excess collagen deposition of a keloid is usually more exaggerated. Microscopically, developed keloids can be differentiated from hypertrophic scars by the presence of large eosinophilic collagen fibers and more abundant mucin. Also, unlike hypertrophic scars, keloids uncommonly undergo involution, and they frequently proliferate well beyond the bounds of the original trauma. Some keloids, particularly on the sternum or upper back, even seem to develop without preceding trauma.
10. Do any factors predispose to hypertrophic scars and keloids?
Many factors can predispose individuals to develop hypertrophic scars and keloids:
• Certain drugs (e.g., isotretinoin) predispose to hypertrophic scarring, and most dermatologic surgeons defer any elective surgery for at least 1 year following discontinuation of isotretinoin.
• The type of injury and degree of tissue injury also play a role. Thermal burns, with their associated severe tissue damage, commonly produce hypertrophic scars or keloids.
• Regional variations exist. Skin that is continuously under tension or tightly stretched over bony protuberances and other anatomic peculiarities predispose to the development of hypertrophic scarring and keloids.
• Dark-skinned races are more prone to both hypertrophic scarring and keloid formation. Blacks are 2 to 19 times and Asians 3 to 5 times more likely than Caucasians to develop keloids. The tendency for multiple keloids to occur in families also suggests a genetic predisposition.
• Certain genodermatoses such as Ehlers-Danlos syndrome, Rubinstein-Taybi syndrome, osteogenesis imperfecta, and progeria have all been reported to have increased risk for the development of keloids.
Table 43-2. Clinical Features That Distinguish Hypertrophic Scars from Keloids
| HYPERTROPHIC SCAR | KELOID |
|---|---|
| Any age group, especially children | Adolescents and young adults |
| All racial and ethnic groups | Blacks and Asians > Caucasians |
| No familial tendency | Familial tendency |
| Limited to sites of trauma | Sites of trauma or spontaneous |
| Onset within 2 months | Onset within 1 year |
| Any anatomic site | High-risk anatomic site |
| Dome-shaped lesions | Dome-shaped, exophytic, or crablike extensions |
| Confined to site of trauma | Extends into normal skin |
| Improved by corrective surgery | Often worsened by surgery |
| Spontaneous regression | No spontaneous regression |
12. Are there effective treatments for hypertrophic scars and keloids?
Various traditional and novel modalities for therapy exist. In general, hypertrophic scars respond well to less aggressive therapy, such as potent topical steroids, intralesional steroids, chronic pressure dressings, and even chronic occlusive dressings with medical Silastic gel sheeting. Some cases may require surgical revision or dermabrasion.
13. What is an acquired digital fibrokeratoma?
These solitary, firm, hyperkeratotic papules most commonly occur around interphalangeal joints but may occur on any site of the hands or feet. They are typically pedunculated and often demonstrate a collarette of hyperkeratosis at the base (Fig. 43-3). Often, they are mistaken clinically for warts or supernumerary digits. Histologically, they demonstrate overlying hyperkeratosis and thickened collagen bundles.
16. What is nodular fasciitis?
Nodular fasciitis (pseudocarcinomatous nodular fasciitis) is a rare, benign, fibroblastic tumor that many consider to be a pseudoneoplastic or reactive growth. It may occur at any age but most commonly presents in young adults as a solitary, rapidly growing, subcutaneous nodule on the extremities. The nodule may be painful, is typically 1 to 3 cm in size, and may adhere to the underlying fascia. Simple excision is curative, but untreated lesions have been documented to regress spontaneously. The importance of this lesion is that, histologically, it may be confused with malignant fibrous neoplasms, because the fibroblasts are large and pleomorphic and mitotic figures are relatively common.
17. What is a connective tissue nevus?
Connective tissue nevus is a term used for cutaneous hamartomas composed primarily of collagen (collagenomas), elastin (elastomas), or a combination of these two. While these are produced by fibroblasts, connective tissue nevi are typically no more cellular than normal dermis. Clinically, they present as one or more dermal papules or plaques. Connective tissue nevi composed primarily of collagen are skin-colored, while those composed primarily of elastin may be skin-colored or yellowish.
18. Why are connective tissue nevi important?
Connective tissue nevi usually do not produce problems, although large lesions may be distressing to the patient for cosmetic reasons. Other patients may become concerned because numerous collagenomas (eruptive collagenomas) develop over a short period of time (Fig. 43-4). However, some of these nevi serve as cutaneous markers for other systemic syndromes. Collagenomas called shagreen patches are frequently seen in patients with tuberous sclerosis. Multiple connective tissue nevi called dermatofibrosis lenticularis disseminata are composed primarily of elastic fibers and are the cutaneous marker for Buschke-Ollendorff syndrome. Buschke-Ollendorff syndrome is an autosomal dominant disorder that presents with osteopoikilosis of the bones and connective tissue nevi.
19. What is the gene defect in Buschke-Ollendorf syndrome?
Recent studies suggest that many but not all patients have a heterozygous, loss-of-function, germline mutation in the LEMD3 gene on chromosome 12q that encodes for a an inner nuclear membrane called LEMD3 or MAN1. The absence of this mutation in some families suggests that there is genetic heterogeneity and further work needs to be done to clarify the genetics of this disorder.
20. What is infantile digital fibromatosis?
Infantile digital fibromatosis is a rare tumor composed of myofibroblasts that develops in infancy and early childhood on the fingers and toes. The primary lesion is a skin-colored or red tumor usually located on the lateral or dorsal surface of the digit. Histologically, they consist of myofibroblasts with characteristic eosinophilic cytoplasmic inclusions composed of actin filaments.
Heymann WR: Infantile digital fibromatosis, J Am Acad Dermatol 59:122–123, 2008.
21. Describe the natural history of infantile digital fibromatosis.
The tumors of infantile digital fibromatosis may grow up to 2 cm but will eventually regress over a period of years (Fig. 43-5). Occasionally, large lesions may produce functional impairment or joint deformities. The recurrence rate is very high, with up to two thirds of all cases recurring following surgical removal. The importance of this tumor is that physicians not familiar with the natural history of this tumor may become overly aggressive and amputate a digit.
22. What is a dermatofibroma?
A dermatofibroma, or fibrous histiocytoma, is the most common fibrohistiocytic tumor of the skin. Usually, these are small, firm, flat, or exophytic papules on the lower extremities of adults. Alhough most commonly 2 to 4 mm in diameter, they can occasionally grow to 2 to 3 cm. They may be skin-colored but more commonly demonstrate tan or brown hyperpigmentation and hypertrophy of overlying epidermis. Nondermatologists frequently mistake them for nevi. Other common locations include the sides of the trunk and upper arms.
Figure 43-5. Infantile digital fibroma. Firm skin-colored nodule with focal hemorrhage on the finger of an infant.
(Courtesy of the Fitzsimons Army Medical Center teaching files.)
Microscopically, most dermatofibromas are composed primarily of fibroblasts that produce abundant collagen. Within some, but not all, dermatofibromas, there are often cellular areas composed of cells with round nuclei that phagocytize lipid or hemosiderin. Multinucleated giant cells may also be present. Dermatofibromas that phagocytize abundant hemosiderin molecules are sometimes referred to as hemosiderotic dermatofibromas or sclerosing hemangiomas (Fig. 43-6).
24. Do dermatofibromas transform into skin cancer?
Dermatofibromas are considered to be benign fibrohistiocytic tumors that do not demonstrate a malignant potential. Though dermatofibromas share clinical and some general histologic similarities with a malignant neoplasm called dermatofibrosarcoma protuberans, histochemical markers show the two are distinct. Although the dermatofibroma itself does not progress into malignancy, the overlying epidermis demonstrates a slight risk to develop into basal cell carcinoma.
25. What is the best way to treat a dermatofibroma?
In general, it is best to avoid treating a dermatofibroma. When a lesion is distressing in appearance, painful, or frequently traumatized, simple excision may be indicated. Several authors have reported successful treatment with cryotherapy. The anticipated benefit of treatment should be weighed against the predictable cosmetic outcome of the therapeutic modality.
Key Points: Fibrohistiocytic Tumors
1. Multiple dermatofibromas are associated with an altered immune status, with the most common cause being systemic lupus erythematosus.
2. Dermatofibromas often demonstrate dimpling with lateral pressure. This has been called a “dimple” or “Fitzpatrick” sign.
26. Are multiple dermatofibromas associated with any internal diseases?
Multiple dermatofibromas have been associated with an altered immune status, with the most common cause being systemic lupus erythematosus and, less commonly, myasthenia gravis and malignancies. These associations are rare and only seen in patients with more than six dermatofibromas; patients presenting with isolated dermatofibromas should not be routinely evaluated for these conditions.
27. What is a “fibrous papule of the nose”?
A fibrous papule of the nose is a relatively common, small (usually 2 to 3 mm), dome-shaped, asymptomatic papule usually located on the lower portion of the nose. The color is variable and may be skin-colored, white, or red. Less commonly, it may occur on other parts of the face. Microscopically, fibrous papules are composed of fibroblasts that may be fusiform, stellate, or multinucleated, and are associated with abundant thick collagen bundles that are oriented around hair follicles or dilated blood vessels. Their greatest significance lies in their clinical similarity to an early basal cell carcinoma. Fibrous papules of the nose are histologically identical to the angiofibromas found in patients with tuberous sclerosis, and most authorities regard fibrous papules to be a solitary form of angiofibroma.
29. What are “giant cell tumors of the tendon sheath”?
Giant cell tumors of the tendon sheath are benign tumors that arise from the fibrous sheath that surrounds the tendons. They typically occur between the ages of 30 and 50 years. They usually develop on the hand, although they may occur on the feet, ankles, and knees. Although they arise from a structure that is deep to the skin, they not infrequently present initially to the dermatologist. The primary lesion is a subcutaneous nodule that appears to be attached to deeper structures (Fig. 43-8). The overlying skin is usually movable but may be fixed in some cases. X-ray examination, besides revealing a soft tissue tumor, may demonstrate cortical erosion in approximately 10% of cases. The treatment of choice is surgical excision.
