A Primary Care Perspective on Keloids

Steven Davidson, MD, DDS; Nasir Aziz, MD, MA, PGY-1; Rashid M. Rashid, MD, PhD, PGY-2; Amor Khachemoune, MD, CWS

Disclosures

Medscape J Med. 2009;11(1):18 

In This Article

Diagnosis and Differential Diagnosis

When an overgrowth of scar tissue is being evaluated, the most immediate differential diagnosis to consider is the hypertrophic scar. Differentiating between the 2 diagnoses is essential because keloids and hypertrophic scars are separate clinical and histochemical entities. Phenotypically, hypertrophic scars remain within the confines of the original scar border, whereas keloids invade adjacent normal dermis.[8] The morphology of the hypertrophic scar is shown in Figure 1.

Two angles of a 40-year-old black woman with a hypertrophic scar following right-sided open cholecystectomy.

Although the scar is inappropriately large, it remains confined to the wound site. In contrast, the keloid grows well beyond the margins of injury (Figure 2).

Close-up of keloid with typical raised area with flat surface. The base is wider than the top.

In addition to morphologic differences, the timeline between the 2 entities differs greatly. Hypertrophic scars generally arise within 4 weeks of the initial scar, grow intensely for several months, and then regress. Figure 3 shows gradual regression of a hypertrophic scar on a patient's lower back.

Young white female with hypertrophic scar at initial presentation (top panels) and after gradual regression (lower panels).

In contrast, a considerable amount of time may elapse before a keloid and an initial scar appear. Beyond this, the keloid may proliferate indefinitely.[6,9]

On histology, both keloids and hypertrophic scars exhibit increased fibroblast density. However, only keloid formation is associated with increased fibroblast proliferation.[9] The collagen fibers in keloids are larger, thicker, and wavier and have a random orientation, whereas those in hypertrophic scars are oriented parallel to the epidermal surface.[10]

Biochemical markers can also distinguish keloids from hypertrophic scars. Concentrations of alanine transaminase and adenosine triphosphate are higher in keloids than in normal scar tissue and hypertrophic scars.[11] Furthermore, fibroblasts isolated from keloids and hypertrophic scars have different mRNA transcription sequences -- keloids have an increased ratio of type I to type III collagen.[12]

Dermatofibrosarcoma protuberans (DFSP), a slow-growing, locally invasive fibrohistiocytic tumor, must also be distinguished from a keloid. It may initially present as a hard, discrete plaque that can range from violaceous to pink and is usually asymptomatic. Like a keloid, DFSP often presents on the trunk and is associated with a history of trauma in up to 20% of cases. Histopathologic examination is often the best way to differentiate between these lesions. DFSP exhibits characteristics of a well-differentiated fibrosarcoma. It consists of densely packed, monomorphous, spindle-shaped cells with elongated nuclei that are organized as fascicles in a storiform arrangement.[13] On the other hand, keloids consist of thickened whorls of hyalinized collagen that lack any particular orientation.

Other diagnoses to consider when examining a keloid-like lesion include dermatofibroma, desmoid tumor, scar with sarcoidosis, and foreign body granuloma.[14]

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