Uncommon case of the acral melanoma with chondro-osseous metaplasia

Aim. This study aimed to improve the diagnostics of acral melanoma and investigate tumor morphological features of the chondroid and osseous matrix. Materials and methods. The article presents a clinical case of metastatic acral melanoma with chondroid and osseous metaplasia in a 60-year-old patient. Cytological, histologic, immunohistochemical, and molecular genetic studies were performed. Results. A conglomerate of lymph nodes was noted in the inguinal region of the patient. Oxyphilic chondroid masses and tumor cells with morphological features of sarcoma were revealed using thin-needle aspiration biopsy. On physical examination, pink-colored subcutaneous neoplasm was discovered in the skin of the heel. Histological examination of the primary neoplasm and inguinal lymph node was performed. Melanoma with chondro-osseous metaplasia was diagnosed. Immunohistochemical examination of the tumor revealed some pronounced diffuse expressions of S-100 protein, HMB-45, and focal expression of Melan A in tumor cells. The sample was tested to detect BRAF mutation, and no mutations were found. Conclusion. Morphological diagnostics of acral melanoma with chondro-osseous metaplasia is characterized by a high risk of diagnostic error. Therefore, additional immunohistological, molecular, and genetic studies should be used in the diagnostics of acral melanoma with chondro-osseous metaplasia.