RESUMEN
INTRODUCTION: Malignant melanoma (MM) is an aggressive neoplasm that may affect pregnant women. Malignant melanoma with small-cell morphology (MMSCM) is a rare variant of MM that can cause confusion in its diagnosis. OBJECTIVE: To report a fatal case of MMSCM in a pregnant woman, highlighting immunohistochemistry (IHC) as a very useful tool in the final diagnosis. CLINICAL CASE: A 22-year-old pregnant female presented with a 5-cm cutaneous tumor in her right leg. The lesion was excised but the patient refused any further therapy. The natural outcome of this neoplasm occurred with local recurrence and multiple metastases to the lungs, liver, and kidneys. CONCLUSIONS: MM should be included in the differential diagnosis of small-cell cutaneous tumor, and IHC is mandatory for diagnosis confirmation. The recommended suggested screening includes, as a minimum, one sensitive marker (S-100 protein) and one specific (HMB45) marker for melanogenesis.