Metastases to dermal and subdermal lymphatics, regional lymph nodes, and the lungs were reported in 3 cases, repectively.43-45 Of these, one primary tumor had received low-dose irradiation in the form of X-ray therapy.45
Treatment Modalities
The cases of EC that we reviewed included treatment with surgical and systemic therapies as well as other modalities such as acitretin, interferon alfa, topical imiquimod, curettage, debridement, electrodesiccation, and radiation. The Table includes a complete summary of the treatments we analyzed.
Surgical Therapy—The majority (91% [105/115]) of cases were treated surgically. The most common treatment modality was WLE (50% [58/115]), followed by amputation (37% [43/115]) and MMS (12% [14/115]).
Wide local excision was the most frequently reported treatment, with excision margins of at least 5 mm to 1 cm.48 Incidence of recurrence was reported for 57% (33/58) of cases treated with WLE; of these, the recurrence rate was 33% (11/33). For patients with EC recurrence, the most common secondary treatment was repeat excision with wider margins (1–2 cm) or amputation (5/11).49-52 Few postoperative complications were reported but included pain, infection, and difficulty walking, which were mostly associated with repair modality (eg, split-thickness skin grafts, rotational flaps).53 Amputation was the second most common treatment modality, with a 67% (29/43) incidence of recurrence. Types of amputation included transmetatarsal ray amputation (7/43 [16%]), foot or forefoot amputation (2/43 [5%]), above-the-knee amputation (1/43 [2%]), and below-the-knee amputation (1/43 [2%]). Complications associated with amputation included infection and requirement of prosthetics for ambulation. Split-thickness skin grafts and rotational flaps were the most common surgical repairs performed.52,53
Mohs micrographic surgery was the least frequently reported surgical treatment modality. Both traditional MMS on fresh tissue and “slow Mohs,” with formalin-fixed paraffin embedded tissue examination over several days, were performed for EC with horizontal en face sectioning.54-56 Incidence of recurrence was reported for 86% (12/14) of MMS cases. Of these, recurrence was seen in 17% (2/12) that utilized a flat horizontal processing of tissue sections coupled with saucerlike excisions to enable examination of the entire undersurface and margins. In one case, the patient was treated with MMS with recurrence noted 1 month later; thus, repeat MMS was performed, and the tumor was found to be entwined around the flexor tendon.57 The tendon was removed, and clear margins were obtained. Follow-up 3 years after the second MMS revealed no signs of recurrence.57 In the other case, the patient had a particularly aggressive course with bilateral VC in the setting of diabetic ulcers that was treated with WLE prior to MMS and recurrence still noted after MMS.26 No complications were reported with MMS.
Overall, recurrence was most frequently reported with WLE (11/33 [33%]), followed by MMS (2/12 [17%]) and amputation (3/29 [10%]). When comparing WLE and amputation, the relationship between treatment modality and recurrence was statistically significant using a χ2 test of independence (χ2=4.7; P=.03). However, results were not significant with Yates correction for continuity (χ2=3.4; P=.06). The χ2 test of independence showed no significant association between treatment method and recurrence when comparing WLE with MMS (χ2=1.2; P=.28). Reported follow-up times varied greatly from a few months to 10 years.
Systemic Therapy—Of the total cases, only 2 cases reported treatment with acitretin and 2 utilized interferon alfa.58,59 In one case, treatment of EC with interferon alfa alone required more aggressive therapy (ie, amputation).58 Neither of the 2 cases using acitretin reported recurrence.59,60 Complications of acitretin therapy included cheilitis and transaminitis.60