Clinical features of 36 cases of amelanotic melanomas and considerations about the relationship between histologic subtypes and diagnostic delay.

BACKGROUND: Amelanotic melanomas (AM) are a difficult diagnostic challenge for clinicians.
OBJECTIVE: To consider the clinical presentation of AM, the histologic subtypes involved, the relationship with the diagnostic delay and the possible involvement in overall prognosis. PATIENTS/
METHODS: Patients who were observed in our department to be affected by cutaneous melanomas were recorded. Sex, age, the clinical features, the site of presentation, the suspected diagnosis, the clinical course, the histological type, the Clark level and the Breslow thickness were recorded. AM were divided in three main clinical types: an erythematous macule or patch on sun-exposed skin, a dermal plaque or nodule without a particular epidermal change, an exophytic nodule. Only pure AM were considered. Histological subtypes considered were superficial spreading melanoma, nodular melanoma, and lentigo maligna melanoma. Diagnostic delay considered from when the patients first noticed the lesion on the site where the melanoma was diagnosed and when the physician or the patient first proposed the removal was recorded. The chi-squared test was used for statistical evaluation with P < 0.05 as level of significance.
RESULTS: Thirty-six cases of AM out of a total of 500 melanomas (7.2%) were collected. The most frequent morphology of clinical presentation was the papulo-nodular form, followed by the plaque form. Mean Breslow thickness of AM was 1.72 mm compared to 0.61 mm of pigmented cases. Nodular histotype was highly represented in AM (30.5% of cases) with respect to pigmented nodular melanomas (2.9%). The diagnostic delay did not differ between amelanotic and pigmented melanomas, nor between nodular AM and nodular pigmented melanomas.
CONCLUSION: The great prevalence of clinical and histological nodular cases, the higher mean Breslow thickness (considered as the most important factor of prognosis) of AM compared with a not significant greater diagnostic delay may point out that a good percentage of AM have an intrinsic faster speed of growth with a worse prognosis irrespectively of the diagnostic performance. The importance of educational campaign for patient and physicians is stressed.