SOX10 Immunostaining in granulomatous dermatoses and benign reactive lymph nodes

SOX10 immunostaining has been considered a highly sensitive and specific marker for melanoma. But there is evidence suggesting that SOX10 positive cells can be present in dermal scars. Therefore, we investigated whether non-melanocytic cell types present in chronic inflammatory processes or benign lymph nodes express SOX10.

We retrospectively selected 20 benign lymph nodes and 20 cutaneous granulomatous dermatoses. SOX10, CD68, and Melan-A immunohistochemistry was performed in all cases.

Scattered SOX10 positivity was found in 85% of lymph nodes, specifically in subcapsular and medullary sinuses and in 85% of granulomatous dermatoses. In granulomatous dermatoses, the Melan-A stain did not label the scattered SOX10 positive cells and it was difficult to determine if CD68 was co-expressed on the SOX10 positive cells. In the lymph nodes, the SOX10 positive cells did not co-express Melan-A or CD68.

We report SOX10 positive cells detected in granulomatous dermatoses and benign lymph nodes. In lymph nodes, SOX10 positive cells were exclusively in subcapsular and medullary sinuses. Therefore, SOX10 is an excellent stain for evaluation of metastatic melanoma with the caveat that positivity in subcapsular and medullary sinuses can be of non-melanocytic origin; the use of additional melanocytic markers is recommended in this situations.