Merkel Cell Carcinoma

"This large tumor presented as a protuberant mass on the buttock of a 45-year-old woman. Microscopically it showed sheets of undifferentiated cells with high nuclear/cytoplasmic ratio, a high mitotic rate, a occasional inconspicuous nucleoli.

Immunostains showed strong dot-like and diffuse cytoplasmic positivity for cytokeratins 20, CAM5.2, and AE1-AE3, as well as granular staining for synaptophysin and chromogranin. There were negative reactions for cytokeratin 7, gross cystic disease fluid protein 15, melan-A, S-100 protein, and thyroid transcription factor 1-alpha.

Even though the histologic features and immunostain profile was characteristic of a primary skin tumor, the presentation is atypical. Usually, Merkel cell carcinoma presents on the sun-exposed areas of elderly individuals. Therefore, the pathologist recommended workup for the possibility of another primary site, including lung, female genital tract, salivary gland, and other cutaneous site."

Courtesy of Dr. Ed Uthman