MUs are more aggressive cutaneous neoplasms compared with other kind of SCCs. The most common risk factor was old burn scars, followed by traumatic wounds, venous stasis ulcers, pressure sores, osteomyelitic fistulas, and other chronic wounds. It is reported that approximately 2% of MUs develop from burn scars [5], and the latency period for the development of malignancy can vary from 11 to 75 years, with an average latency of 31 years [6, 7]. Interestingly, the incidence of MUs in males is approximately three times higher than that in females, with the peak occurrence is in the fifth decade of life [3].
Occurrence of MU may be multifactorial, including a depressed immune system, chronic irritation and impaired immunologic reactivity to tumor cells, all of which work together to promote malignant transformation of the ulcer. Thus, as soon as MUs was suspected, biopsy of multiple areas should be considered in cases of chronic or non-healing ulcers [8]. Biopsy histopathology of MU results in identification of SCC in the majority of cases (76%), followed by basal cell (approximately 12%) and melanoma (approximately 6%).
Treatment and prognosis of MU depends on tumor tissue type and whether there is co-existent metastasis. For example, treatment of well-differentiated lesions involves local excision which has a good prognosis [9]. However, patients with lymph node metastasis are better suited for wide excision or amputation, and even the ulcer might recur, especially within 3 years, resulting in a significant reduction of 3-year survival rate from 35–50% [10]. In our case, given the patient without lymph node metastasis, the patient received the local excision of lesion. Differently, we have adopted the regimen of staged surgical reconstruction for patient to adequately remove necrotic tissue and infectious lesions, and then also tried a strategy of skin stretching before skin grafting to reduce skin transplantation area and further boost skin transplant survival. However, given the involvement of the right knee joint and surrounding skin scarring caused by the prior burn, simple skin expansion failed to achieve adequate results, but the wound obtained good recovery. Therefore, treatment of similar lesions located in non-joint regions may also benefit from skin stretching to promote wound repair after surgical excision.
Taken together, MUs are the rare tumor with higher aggressive, rates of local recurrence and metastasis, and wide local excision with skin grafting is the most common surgical procedure. In this case, we provided an improved treatment protocol for the MUs patient with chronic non-healing wounds, which might be beneficial to these patients.