mart-1-antigen and Keratosis--Actinic

Benign lichenoid keratosis (BLK) is a cutaneous lesion that can clinically mimic malignancy and may represent regression of a pre-existing lesion. BLK may show epidermal pseudo-nests prompting evaluation for a melanocytic lesion. False positivity of MART-1/Melan-A immunostaining in pseudonests has been showed; however, the value of SRY-related HMG-box 10 (SOX10) staining in BLK with features suspicious for a melanocytic proliferation has not been previously reported.. Twenty-one cases of BLK from 2015 to 2020 were identified. Slides were reviewed and SOX10 immunohistochemistry was performed on each case. Subsequently, Melan-A immunohistochemical staining was performed on all cases.. In 10 cases (47.6%), unexpected SOX10 staining was seen in rare to numerous small, single cells in the epidermis above the basal cell layer. No malignancy was identified. Of the 10 cases, 8 (80%) showed suprabasal SOX10 staining did not show similar suprabasal Melan-A staining; 2 (20%) cases showed scattered suprabasal cells positive for Melan-A.. SOX10 immunostaining in BLK can highlight scattered cells in the epidermis (not easily noticeable on routine stain). Performing SOX10 immunostain alone on BLK can prompt a misdiagnosis of a melanocytic lesion and should be done with caution.

Topics: Acanthoma; Biomarkers, Tumor; Humans; Keratosis, Actinic; MART-1 Antigen; Melanocytes; Skin Diseases; Skin Neoplasms; SOXE Transcription Factors

Histologic differentiation of melanoma in situ (MIS) from solar keratosis on chronically sun-damaged skin is challenging. The first-line immunostain is usually MART-1/Melan-A, which can exaggerate the epidermal melanocytes, causing a diagnostic pitfall for MIS. By comparing MART-1 and SOX10 immunostaining, we scored the percentage of epidermal melanocytes per 2-mm diameter fields in pigmented actinic keratosis (n = 16), lichenoid keratosis (n = 7), junctional melanocytic nevus (n = 6), keratosis with atypical melanocytic proliferation (n = 17) and MIS (n = 10). These cases represented an older population (68 years median age) and the head and neck (50%) was the most common anatomic site. MART-1 score was significantly higher than SOX10 (P value <.05) in solar keratoses, but showed no difference in detecting melanocytic proliferations, demonstrating their equal detection rate of melanocytes. The sensitivity of both MART-1 and SOX10 was 100%, while their specificities were 17% and 96%, respectively. These results show that SOX10 is more specific than MART-1 in distinguishing epidermal melanocytes on sun-damaged skin by avoiding overdiagnosis of melanoma.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Female; Humans; Hyperplasia; Immunohistochemistry; Keratosis, Actinic; Male; MART-1 Antigen; Melanocytes; Melanoma; Middle Aged; Sensitivity and Specificity; SOXE Transcription Factors; Sunlight

Actinic keratosis (AK) and squamous cell carcinoma in-situ (SCCIS) within or near melanoma in situ (MIS) can complicate diagnosis due to overlapping clinical and microscopic features. This study aimed to describe basilar melanocyte density and pagetoid spread in AK and SCCIS for improved diagnostic accuracy.. A total of 22 AK and 22 SCCIS biopsies containing a margin of uninvolved epidermis were immunostained with MART-1 (melanoma antigen recognized by T-cells 1). The basilar melanocyte:keratinocyte ratio and the number and distribution of pagetoid melanocytes were compared in AK, SCCIS, and uninvolved epidermis. An in-vitro human skin model was created to assess the impact of keratinocyte atypia on melanocyte distribution.. The median basilar melanocyte:keratinocyte ratio in SCCIS (1:11.49) was lower than in uninvolved epidermis (1:5.59, P = 0.0011), and the ratio in AK (1:6.94) was similar to uninvolved epidermis (P = 0.987). Pagetoid melanocytes were absent in perilesional skin but common in AK (21/22, P < 0.0001) and SCCIS (22/22, P < 0.0001). Pagetoid melanocytes at or above the mid-spinous layer were more common in SCCIS (21/22) vs AK (7/22, P < 0.0001). Pagetoid melanocytes were present in the in-vitro skin model made with neoplastic but not normal keratinocytes.. Pagetoid melanocytes in AK and SCCIS should be interpreted with caution to avoid overdiagnosis of MIS.

Topics: Adult; Aged; Biomarkers, Tumor; Carcinoma in Situ; Carcinoma, Squamous Cell; Diagnostic Errors; Female; Humans; Keratinocytes; Keratosis, Actinic; Male; MART-1 Antigen; Melanocytes; Melanoma; Middle Aged; 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