Basal cell carcinoma from a malignant melanoma scar

Abstract

Many individuals with localized melanoma undergo wide local excision and live many years with the surgical scar. The present case describes a basal cell carcinoma arising from a malignant melanoma excision scar. There are no similar reports in the literature. A 69-year-old female with a 25-year remote history of localized melanoma treated with wide local excision presents with two new lesions overlying the scar. The lesions were confirmed to be a basal cell carcinoma and dysplastic nevi on punch biopsy. Complete scar excision is performed. This report warns of the possibility of secondary primary malignancy arising from within the scar of a previous malignancy excision. With any changes to a scar, a prompt biopsy should be performed and treatment administered appropriately depending on the diagnosis.

Introduction

Melanoma is a highly aggressive form of skin cancer affecting young and older patient populations. Its incidence is increasing worldwide. ¹ For individuals diagnosed with localized melanoma, first-line treatment is wide local excision. Because melanoma is a common cancer of individuals aged 15–30 years, ¹ the surgical excision site is clinically followed over decades. While local recurrences and in-transit lesions are well described, the development of a second cutaneous malignancy arising in the surgical scar of a melanoma has not been reported.

Basal cell carcinoma (BCC) is the most common malignant tumor worldwide and may be associated with significant morbidity through local destruction and recurrence. Prompt diagnosis and treatment are important. BCC is known to develop from environmental factors (sun exposure, radiation), patient factors (genetic syndromes, skin phenotype), prior trauma, and scar tissue. ² There are no reports of BCC arising in the excision site scar of a melanoma.

In the present report, a BCC arising in a 25-year-old surgical scar of an invasive melanoma is described, and it is the first report of a BCC developing in the scar of a melanoma.

Patient information

The patient is a 69-year-old female, known for remote Stage 2A invasive melanoma of the left anterior thigh, treated in 1988 with wide local excision. She presents to her dermatologist’s office for an annual integument check. The patient’s past medical history is significant for a previous lip BCC (excised in 2022). The patient’s family history is significant only for her mother having BCC. The patient’s skin cancer risk factors included Fitzpatrick Type I skin type, outdoor sun exposure while working on a farm during childhood without sun protection, and a remote 5-year smoking history.

Clinical findings, diagnostic assessment, and therapy

The patient did not present with any symptoms; the visit was an annual dermatology check. On the left anterior thigh was a 3.5 cm well-healed melanoma scar, with a centrally located 0.5 cm erythematous macule, and a laterally located 0.5 cm pigmented macule (Figure 1(a)). Palpable adenopathy was absent.

Figure 1.

(a) A close-up photo of healed melanoma scar demonstrating the two punch biopsy scar sites: (i) the central lesion is a basal cell carcinoma, and (ii) the lateral lesion is an atypical nevus. (b) The photograph demonstrates the patient’s site of complete scar excision, 6 months of follow-up.

The patient was not aware of any changes to the lesions and was unaware of the duration of the new lesions.

Based upon her past medical history, a recurrent melanoma was considered. The differential diagnosis included non-melanoma skin cancer (BCC, squamous cell carcinoma), and benign lesions, including trauma, nevus, and scar. Both lesions were punch biopsied. Pathology of the central macule revealed a BCC, superficial type, and scar tissue (Figure 2(a)). Pathology of the lateral macule demonstrated a compound dysplastic nevus with mild cytoarchitectural atypia (Figure 2(b)).

Figure 2.

(a) The pathology slide of the basal cell carcinoma, superficial type. Scar tissue is present. (b) The pathology slide of a compound dysplastic nevus, which demonstrates mild cytoarchitectural atypia. The lesion is completely excised in the planes of section examined.

A definitive excision of the entire scar, encompassing both lesions, was completed with a 3–4 mm margin. The surgical final pathology of the tissue confirmed the biopsy diagnosis of each lesion and reported all margins negative.

The patient healed well and is clinically clear 13 months post-operation without any complications (Figure 1(b)). She continues to have her integument monitored regularly.

Discussion

The present case is the first report of a BCC arising in the scar of a melanoma, which was excised 25 years previously. The present case was managed by complete scar excision and primary closure, with no complication or tumor recurrence.

Previous studies have established that scars may create a permissive environment for neoplastic transformation, with chronic inflammation, fibroblast activation, and extracellular matrix remodeling implicating a scar-associated tumorigenesis. In the case of a BCC, pathogenesis may involve mobilization of stem cells out of their normal microenvironment and into the interfollicular epidermis. ² It is estimated that 7.3% of BCC arise from scarring and trauma, ² and BCC has been documented in remote surgical scars. ² The present case involved several patient risk factors, including advanced age, personal BCC history, family history, and Fitzpatrick skin type 1. While UV exposure is the strongest etiologic factor, explaining the predilection of BCC for the head and neck—this case occurred on the lower extremity. Altogether, a causal link from a single case cannot be established, and there is a probable influence of multifactorial etiology; the association of a BCC arising from a melanoma scar represents a novel finding.

The development of BCCs arising adjacent to melanomas is a phenomenon known as “collision tumors.” These tumors are defined by the presence of two or more distinct neoplasms that are adjacent or intermingled in the same cutaneous site. ³ In such cases, the most common malignant tumor associated with BCC is invasive melanoma. ³ It is interesting in this case that the BCC arose adjacent to a dysplastic nevus. This observation aligns with the “microenvironment” theory, which posits that the first tumor induces epithelial or stromal changes, thereby creating a local environment conducive to the development of a second tumor. ³ The clinical scenario raised concern for subsequent malignant changes occurring within the scar, and complete scar excision was deemed to be reasonable management. This management strategy differs from previously reported cases of BCCs from surgical scar, where excision was typically limited to the tumor itself.

This case expands the differential diagnosis of an evolving melanoma scar to include skin malignancies. This is especially in the context of the lifelong management of melanoma survivors, who require long-term scar observation and have potential skin cancer risk factors. Any new lesion developing in a melanoma scar should prompt a biopsy for definitive diagnosis and lead to the most appropriate management, as was done in the present example. The differential diagnosis could also consider benign and lymphoproliferative disorders, as evidenced by published reports of lichen planus ⁴ and cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoproliferative disorder ⁵ arising from melanoma scars.

Conclusion

This case reinforces the importance of annual skin surveys and long-term surveillance of the melanoma surgical scar. With any new scar changes, melanoma recurrence or second primary malignancy must be ruled out with a prompt biopsy to confirm the diagnosis. Finally, it is reasonable to offer complete scar excision to the patient, encompassing the scar that is changing and any adjacent concerning lesions.

Patient perspective

The patient appreciated the prompt diagnosis of the lesion to her melanoma scar. She appreciated having complete scar excision offered as an option and feels “peace of mind.” She is happy with the wound appearance and reports no complications.