Myeloid Sarcoma Versus Epithelioid Angiosarcoma: A Case Report of a Potential Diagnostic Pitfall.

The likely first question to ask when encountering a soft tissue tumor for the first time is simply, "Is this carcinoma or sarcoma?" Lesions of unknown etiology should also nearly always include melanoma as a differential diagnosis due to its greatly elusive nature, and this case report reinforces the importance of also keeping a lymphoproliferative process at the forefront of one's mind while considering the possible overlapping features with other entities. We present a 64-year-old man with a soft tissue mass of the supraspinatus that was perceived as an epithelioid angiosarcoma due to the largely epithelioid morphology and characteristic immunohistochemical profile. However, given the patient's pertinent hematologic history and an additional array of immunohistochemical stains, the neoplasm was regarded as a myeloid sarcoma. Much like melanomas, lymphomas can present in a number of different forms and fashions. Namely, myeloid sarcomas-a mass-forming neoplasm composed of myeloid blasts effacing the surrounding tissue architecture-can masquerade as a carcinoma or sarcoma not only morphologically, but also immunohistochemically. We consider the pitfalls experienced with this entity and further elaborate on the genetics discovered within this particularly challenging lesion.