Primary cardiac tumors are rare because metastatic lesions from distant sites account for most masses. We are reporting two cases of malignant intracardiac masses with their diagnostic dilemma. Our first patient is a 72-year-old male with a pertinent history of desmoplastic and spindle cell melanoma who presented after his surveillance positron emission tomography (PET) scan showed a hypermetabolic lesion in the inferior pericardium. The initial impression for this mass is recurrent malignant melanoma. After an initial negative endometrial biopsy, the patient underwent debulking surgery, and pathology revealed high-grade spindle cell sarcoma. The patient underwent chemotherapy but had a disease progression and ultimately elected hospice care. Our second patient is a 75-year-old male with a history of stage IB adenocarcinoma of the lung who presented with progressive dyspnea. An echocardiogram revealed a moderate-sized left ventricular mass. Initial assessment based on tumor morphology and location suggested possible cardiac sarcoma. However, the patient's subsequent cardiac biopsy revealed small cell carcinoma, likely of primary cardiac origin, as no other primary nidus of the tumor was seen. Based on this result, the patient has been started on carboplatin, etoposide, and atezolizumab and responded well as of the writing of this manuscript. Given the rarity of malignant primary cardiac tumors and their variable clinical presentation, intracardiac masses are often diagnosed incidentally. In addition, given the high risk of biopsy for intracardiac masses, a presumptive diagnosis is rendered via imaging techniques. However, most of these tumors have no pathognomonic imaging findings, and their diagnosis relies heavily on physician interpretation and experience. Our case series illustrated the unpredictable nature of noninvasive methods and that even endometrial biopsy can return a false negative. Therefore, it is essential to be persistent in obtaining a pathological diagnosis, especially if the clinical picture is unclear. While these more invasive methods present the challenge of identifying whether the procedure is truly needed and locating a skilled operator, it could change the diagnosis entirely and open the patient up to new therapies.