A 64-year-old man presents with a history of weight loss and progressive yellowing of the skin and sclera. Ultrasound examination of the liver shows multiple lesions. A fine needle aspiration is performed under ultrasound guidance. The smear discloses numerous round cells, with poorly defined cytoplasm, eccentric nuclei, and prominent nucleoli. The cytoplasm of these cells contains pigment granules as shown in the image. Immunohistochemical stains are positive for the HMB-45 antigen. What is the appropriate diagnosis?
Answer : D Metastatic melanoma
The brown pigment in the cytoplasm is composed of fine melanin granules, which is characteristic of malignant melanoma.
HMB-45 antigen is commonly expressed in melanoma cells. Intracellular pigment is not encountered in the other choices.