Desmoplastic Melanoma in African American Patients

Desmoplastic melanoma (DM) is an uncommon fibrosing variant of melanoma typically found on chronically sun-damaged skin of elderly white patients.¹ However, it can also affect other ethnic groups and occur at a younger age and/or on sun-protected sites.¹ Familiarity with DM is relevant for clinicians and pathologists because, for the unwary, it may be confused with a benign lesion such as a fibroma or scar, leading to delayed diagnosis of melanoma.¹ We report herein 3 cases of DM in African American women.

Of 249 patients with DM seen at a cancer center, 3 African American patients were found. All 3 were women. At the time of diagnosis, they were 33, 39, and 78 years old (Table), and the tumors were located on the cheek, forearm, and back, respectively. The clinical differential diagnosis included cyst, scar, and fibroma. All patients underwent wide surgical excision of the tumors with negative margins. None of the patients underwent sentinel lymph node mapping.

All tumors showed classic histopathologic findings of DM: a paucicellular fibrosing spindle-cell proliferation in the dermis and subcutis associated with lymphoid aggregates (Figure 1). Areas with bland fibromalike features (Figure 1B) were identified as were areas with enlarged hyperchromatic fusiform cells (Figure 1C). All tumors were immunoreactive for S-100 protein.

Two of the lesions were histologically pure DM, with a uniform paucicellular fibrosing phenotype throughout the entire tumor mass (Figure 1). One of the tumors was a mixed variant of DM, which contained both paucicellular spindle-cell areas and hypercellular epithelioid-cell foci (Figure 2).

Tumor thicknesses ranged from 4.7 to 10.5 mm. Mitoses were rare. All tumors showed perineural invasion. None was associated with solar elastosis, vascular invasion, or satellites.

Desmoplastic melanoma is an important subtype of melanoma because it represents a diagnostic pitfall and has a distinct clinical behavior.¹ It has a higher rate of local recurrence and lower incidence of sentinel lymph node involvement than conventional melanoma, especially if the DM is histopathologically pure in appearance.^2,3 It is of interest that the DMs of the 3 African American women described herein lacked an associated intraepidermal (in situ) melanoma component as well as evidence of solar elastosis, which suggests a cause independent of chronic sun damage.

Most melanomas in African Americans are acral tumors or melanomas of superficial spreading type. Based on Surveillance, Epidemiology, and End Results (SEER) data (1992-2002), 7 of 251 primary invasive melanomas of African Americans were reported as desmoplastic.⁴ However, they were not further characterized with regard to histopathologic subtype (pure vs mixed) or anatomic site. One case report of a tumor said to be desmoplastic was an acral melanoma.⁵ After review of its histopathologic illustrations, we interpret it as a mixed DM.⁵

Herein, we report for the first time to our knowledge the occurrence of pure DMs at nonacral sites in African American women.

Correspondence: Dr Busam, Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021 (busamk@mskcc.org).

Author Contributions: All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Busam, Ariyan, and Coit. Acquisition of data: Busam, Ariyan, and Coit. Analysis and interpretation of data: Busam, Ariyan, and Coit. Drafting of the manuscript: Busam. Critical revision of the manuscript for important intellectual content: Ariyan and Coit. Administrative, technical, and material support: Busam, Ariyan, and Coit.

Financial Disclosure: None reported.

Additional Contributions: Kita Scott, BA, assisted with queries of the institutional melanoma database; Allyne Manzo helped with the digital images; and Jason Bini provided administrative assistance.