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Melanosomal alterations in dysplastic melanocytic nevi. A quantitative, ultrastructural investigation
A R Rhodes1, Y Seki, T B Fitzpatrick
1Department of Dermatology, Massachusetts General Hospital, Boston 02114.
Abstract:
Abnormal-looking melanosomes are observed commonly in both intraepidermal melanocytes of cutaneous melanoma and dysplastic melanocytic nevi (DMN). This was investigated by using transmission electron microscopic examination to determine the percentage of abnormal melanosomes among 8267 melanosomes assessed in at least five solitary intraepidermal basal unit melanocytes from each of five specimens of DMN, superficial spreading melanoma (SSM), common acquired nevomelanocytic nevi (NMN), and normal skin (NS) adjacent to DMN. The percentage of abnormal melanosomes in DMN (mean + SD, 44 + 23%) was seven times greater than that in NMN (6 + 7%) and 22 times greater than that in NS (2 + 5% [P less than 0.001, both comparisons]), but only 80% that in SSM (57 + 19% [P less than 0.02]). Melanocyte area, nuclear area, and the ratio of nuclear area to cytoplasmic area did not account for the observed differences. Melanosomal alterations may be a useful marker of atypicality in melanocytic tumors.
Insights
Dysplastic melanocytic nevi (DMN) and melanoma show significantly more abnormal melanosomes than normal skin or common acquired nevomelanocytic nevi. These melanosomal alterations may serve as a key marker for atypical melanocytic tumors.
Area of Science:
- Dermatopathology
- Melanoma Research
- Cell Biology
Background:
- Abnormal melanosomes are frequently observed in intraepidermal melanocytes of cutaneous melanoma and dysplastic melanocytic nevi (DMN).
- Distinguishing between benign and malignant melanocytic lesions is crucial for patient outcomes.
Purpose of the Study:
- To quantify and compare the percentage of abnormal melanosomes in dysplastic melanocytic nevi (DMN), superficial spreading melanoma (SSM), common acquired nevomelanocytic nevi (NMN), and normal skin (NS).
- To evaluate the potential of melanosomal alterations as a diagnostic marker for atypical melanocytic tumors.
Main Methods:
- Transmission electron microscopy was employed to assess 8267 melanosomes.
- Analysis was conducted on intraepidermal basal unit melanocytes from five specimens each of DMN, SSM, NMN, and adjacent NS.
Main Results:
- Dysplastic melanocytic nevi (DMN) exhibited a significantly higher percentage of abnormal melanosomes (44% ± 23%) compared to common acquired nevomelanocytic nevi (NMN) (6% ± 7%) and normal skin (NS) (2% ± 5%).
- The percentage of abnormal melanosomes in DMN was approximately 80% of that observed in superficial spreading melanoma (SSM) (57% ± 19%).
- Melanocyte and nuclear areas, as well as nuclear-to-cytoplasmic ratios, did not explain these observed differences.
Conclusions:
- Melanosomal alterations are significantly more prevalent in dysplastic melanocytic nevi (DMN) and melanoma compared to benign nevi and normal skin.
- Abnormal melanosome morphology represents a potential diagnostic biomarker for assessing atypicality in melanocytic tumors.