Case of the Month: March 2022
posted: March 21, 2022
This is a 69-year-old patient with a remote history of skin cancer in his knee area, status post excision, nivolumab treatment and radiation therapy. Follow-up PET scan shows disease progression in the retroperitoneal lymph nodes as well as a PET positive jejunal lesion. Endoscopy findings demonstrate a single 9 mm polyp in the jejunum. Biopsy from the small bowel is shown below.
Immunostains
Final Diagnosis: Merkel Cell Carcinoma
Merkel cell carcinoma (MCC) is an uncommon cutaneous malignant tumor that presents as a rapidly growing skin nodule on sun-exposed areas of the body. MCC is aggressive disease with regional nodal and distant metastases to lung, bones and GI tract. The patient’s initial knee lesion was biopsy proven MCC. This malignant skin lesion is defined by both neuroendocrine and epithelial differentiation as demonstrated by immunopositivity for perinuclear cytokeratin 20 expression and neuroendocrine markers like chromogranin and synaptophysin.