Multimodal Pathologic Diagnosis of Malignant Melanoma: Integration of Morphology, Histochemistry , Immunohistology, and Electron Microscopy

Abstract

The diagnosis of malignant melanoma continues to be a challenging one in selected cases, particularly when it assumes an amelanotic appearance and presents itself in a clinically atypical fashion. Histochemical methods for the identification of melanin, including Schmorl's technique and the Fontana-Masson procedure, are still helpful, yielding positivity in 25–30% of amelanotic tumors. Moreover, a growing panel of immunohistologic reagents that label melanomas is now available, including antibodies to S100 protein isoforms; HMB-45, HMB-50, MART-1, and other gp100 markers; tyrosinase; and microphthalmia transcription factor-1. When histochemical and immunohistologic assessments are indeterminate or contradictory, electron microscopy continues to be a valuable modality of study, revealing the presence of premelanosomes in most melanomas if adequate sampling of the turnor is performed. (The J Histotechnol 26:253, 2003)

Keywords:

• melanocytic neoplasms
• immunohistology
• histochemistry
• electron microscopy