Could it still be malignant melanoma or just a poorly differentiated neoplasm?

Abstract

The present case, characterised by an aggressive and poorly differentiated skin malignancy, contributes to a wider discussion on such tumours. Despite repeated histological examinations, including immunohistochemistry, and thorough radiological investigation, diagnosis of melanoma was not easy.

Figure 1

High power views of the tumour showing severely pleomorphic cells with large vesicular nuclei, prominent nucleoli and eosinophilic cytoplasm. Frequent mitoses are evident.

Figure 2

Melan-A (a melanocytic marker) immunohistochemistry is negative within the tumour.

Figure 3

S100 (a melanocytic marker) immunohistochemistry is negative within the tumour.

Figure 4

Tumour cells strongly express vimentin (on immunohistochemistry).

Figure 5

Recurrent disease with ulcerated new nodule.

Figure 6

A melanoma from another patient showing nests of atypical epithelioid melanocytes within the dermis and epidermis.