Myeloid sarcoma mimicking as recurrent squamous cell carcinoma: What is the etiology?

Abstract Introduction/Objective Myeloid sarcoma is an extramedullary malignancy of primitive myeloid cells and can occur during, preceding, or as a relapse of acute myeloid leukemia that occurs mostly in the soft tissue and skin. Methods/Case Report A 77-year-old white male with a history of oral squamous cell carcinoma status post resection (18 months ago) followed by radiation and chemotherapy (15 months prior), presented to the ear nose and throat clinic with increasing weakness and dizziness. He received two doses of Cisplatin and was currently on Pembrolizumab. On examination, there were two lesions in the oral cavity, one on the right gingivobuccal sulcus and a second on the left posterior mandibular ridge, suspicious for squamous cell carcinoma recurrence. Interestingly, the biopsy did not show evidence of recurrent squamous cell carcinoma but showed sheets of blasts that were positive for MPO, CD117, CD43, and CD68, consistent with myeloid sarcoma. Subsequent peripheral blood and bone marrow examinations showed acute myeloid leukemia. Results (if a Case Study enter NA) NA Conclusion Myeloid neoplasms post-cytotoxic therapy (MN-pCT) occur after radiation, alkylating agents, DNA topoisomerase II inhibitors, antimetabolites, and PARP1 inhibitors for a non-myeloid malignancy. Topoisomerase inhibitors are associated with MN-pCT after a latency period of 1 to 3 years; alkylating agents and radiation are associated with MN-pCT after a latency period of 5 to 7 years. Interestingly, this patient developed myeloid sarcoma in a previously irradiated area within 2 years. Cisplatin was discontinued after 2 doses due to side effect complications and is unlikely to be the culprit. Pembrolizumab is not considered to be a cytotoxic therapy and has not been reported to be associated with MN-pCT, however, the latency period for radiation-induced MN-pCT is unusually short in this patient and this raises the possibility of a Pembrolizumab-induced secondary myeloid neoplasm; additional investigation with other patients on this medication with second subsequent malignancies is required.