In a literature review published by Pampena et al in JAMA Dermatology, researchers provided detailed and extensive information about the features of several different kinds of rare cutaneous melanomas.
According to the researchers, the analysis was performed to “…provide a comprehensive overview of the specific clinical and dermoscopic features of each variant of the most frequently reported but uncommon melanomas, improving clinician skill to recognize these variants.” They also added that due to a lack of information on these subtypes, accurate diagnosis sometimes proved to be difficult.
Methods
Researchers used PubMed, Embase, and Cochrane Central Register of Controlled Trials to perform a two-step literature review. In step one, researchers looked for instances in the databases where at least one case reporting dermoscopy was published in medical literature for uncommon melanoma variants. In step two, each uncommon disease variant— amelanotic, hypopigmented, animal, melanocytoma, balloon, desmoplastic, follicular, nested, nevoid, dermal, spitz, spindle, and verrucous—was searched for in the databases with the combination of the words "melanoma," "dermoscopy,"and "dermatoscopy." These database searches were conducted from time of database inception until November 2018.
The researchers also searched their own dermatology clinic’s database for histopathologically confirmed cases of the uncommon variants. The clinic’s database search ranged from 2012 to 2019.
Findings
From the group of three databases, the researchers identified 62 articles reporting 433 cases of melanoma. From the clinic database, 56 additional cases were identified, bringing the total cases of melanoma to 483.
From the searches, the following cases were identified:
- Two hundred and eighty-three cases of amelanotic superficial spreading melanoma
- Eighteen cases of animal-type and pigmented epithelioid melanocytoma
- Seven cases of balloon cell melanoma
- Seventy-one cases of desmoplastic melanoma
- Three cases of follicular melanoma
- Ten cases of nested melanoma
- Thirty-three cases of nevoid melanoma
- Two cases of primary dermal melanoma
- Fifty-seven cases of spitzoid melanoma
- Five cases of verrucous melanoma.
Uncommon variants of melanoma were more frequently reported in women than in men (147 cases vs 132 cases, respectively). The mean age of patients with these lesions was 58 years. Most of the lesions were palpable, and nearly 60% of the cases were amelanotic on both clinical and dermoscopic examination. The authors noted that on clinical examination, these lesions “could resemble other benign or malignant skin conditions,” and that dermoscopy “typically revealed a homogeneous pinkish background, white structures, and polymorphic vessels.”
The authors concluded, “Uncommon melanoma variants may resemble both inflammatory disorders and other cutaneous neoplasms, representing a diagnostic pitfall even for the most experienced dermatologist…Our systematic review represents, to our knowledge, the largest comprehensive overview of specific clinical and dermoscopic features of a series of uncommon melanoma variants. This overview may help clinicians recognize these uncommon and tricky-to-diagnose variants that frequently simulate other benign or malignant skin lesions.”
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.
