mart-1-antigen and Lentigo

Evaluation of cutaneous pigmented lesions can be diagnostically challenging and represents an activity often supplemented by immunohistochemistry. Immunohistochemical studies typically employ 3,3'-diaminobenzidine (DAB) resulting in brown staining of both melanocytes and melanin. Difficulty may thus arise in distinguishing different cell types in heavily melanized lesions. Azure blue counterstaining has been used in conjunction with melanoma antigen recognized by T-cells (MART-1) to differentiate melanocytes from melanin by highlighting the latter blue-green. Microphthalmia transcription factor (MiTF) represents an alternative immunomarker that shows nuclear reactivity, which facilitates ease of interpretation.. Twenty examples of solar lentigo and melanoma in situ (MIS) were independently evaluated utilizing MiTF and MART-1/Azure blue for melanocyte quantification. Melanocyte counts were averaged over five high-power fields (×400) to obtain a mean melanocytic count.. There was no significant difference in the mean melanocytic count between MART-1/Azure blue and MiTF as assessed in the solar lentigo group and as assessed independently in the MIS group. MiTF nuclear staining facilitated interpretation and required less laboratory preparation, as an additional counterstain was not necessary.. MiTF is as effective as MART-1/Azure blue in identifying melanocytes in the context of solar lentigo or MIS. On the basis of our results, we favor expanding the use of MiTF as an immunohistochemical marker, as it provides an efficient alternative to MART-1 with Azure blue counterstaining in the evaluation of cutaneous pigmented lesions.

Topics: Azure Stains; Biomarkers, Tumor; Carcinoma in Situ; Diagnosis, Differential; Humans; Immunohistochemistry; Lentigo; MART-1 Antigen; Melanoma; Microphthalmia-Associated Transcription Factor; Skin Neoplasms

It is often challenging to reliably assess the number of lesional melanocytes in intraepidermal melanocytic proliferations involving sun-damaged skin. Therefore, dermatopathologists routinely use immunostains to help differentiate melanocytes from surrounding keratinocytes.. Forty-three cases of solar lentigo or melanoma in situ (of the lentigo maligna type) were retrospectively chosen (20 melanomas in situ and 23 solar lentigo). Microphthalmia transcription factor (MiTF), HMB-45, Melan-A and Mel-5 immunostains were performed with an Azure blue counterstain, and the mean melanocyte counts were calculated within a 1-mm segment of epidermis.. In solar lentigines, the mean melanocyte counts were 27 (MiTF), 23 (HMB-45 and Mel-5) and 41 (Melan-A), as compared to hematoxylin and eosin (H&E) (25). In melanoma in situ, the mean melanocyte counts were 112 (MiTF), 149 (Melan-A), 111 (HMB-45) and 80 (Mel-5), as compared to H&E (109).. These results show that Melan-A significantly overestimates the density of melanocytes within dermatoheliotic skin. Compared to other tested stains, nuclear staining MiTF allowed greater distinction of melanocytes from keratinocytes with melanized cytoplasm. These findings indicate that MiTF is a superior marker for quantification of melanocytes in the evaluation of subtle intraepidermal melanocytic proliferations and in the differential diagnosis of solar lentigo.

Topics: Aged; Aged, 80 and over; Biomarkers, Tumor; Cell Count; Cell Nucleus; Diagnosis, Differential; Female; Glycoproteins; gp100 Melanoma Antigen; Humans; Keratinocytes; Lentigo; Male; MART-1 Antigen; Melanocytes; Melanoma; Melanoma-Specific Antigens; Microphthalmia-Associated Transcription Factor; Middle Aged; Reproducibility of Results; Retrospective Studies; Skin Neoplasms

Distinguishing lentigo maligna from solar lentigo, and pigmented actinic keratosis can sometimes be problematic. Melan-A is an immunohistochemical marker which that can be helpful in decorating the melanocytes of pigmented lesions. A recent report has suggested that Melan-A may spuriously label nests of junctional keratinocytes, potentially leading to the misdiagnosis of melanoma in situ. We compared Melan-A immunohistochemical staining in pigmented actinic keratosis , non-pigmented actinic keratoses , melanoma in situ of lentigo maligna type and solar lentigines. We found a statistically significant increase of Melan-A staining in melanoma in situ, but no statistical difference in the number of junctional Melan-A positively staining cells, in solar lentigines, pigmented actinic keratoses, and non-pigmented actinic keratoses, respectively. In the non non-melanoma samples, the Melan-A A-positive cells located at the dermal-epidermal junction were interspersed and not observed in clusters. Increased staining with Melan-A, in an actinic keratosis, or solar lentigo should raise the possibility of a contiguous melanoma in situ.

Topics: Aged; Antigens, Neoplasm; Biomarkers, Tumor; Humans; Hutchinson's Melanotic Freckle; Immunohistochemistry; Keratosis, Actinic; Lentigo; MART-1 Antigen; Melanoma; Middle Aged; Neoplasm Proteins; Skin Neoplasms