Hidden Heart Clot Detected Before Chemotherapy in Young Hodgkin Lymphoma Patient

A 21-year-old woman walked into a hematology clinic with the classic warning signs of lymphoma: swollen, painful lymph nodes in her neck, drenching night sweats, relentless itching, and an unintentional weight loss of eight kilograms in a single month. What her medical team at the University of Padua went on to discover, however, was far stranger than the lymphoma itself. Before a single dose of chemotherapy had been given, routine pre-treatment imaging revealed a large, multilobulated mass clinging to the wall of her right atrium, the chamber that receives oxygen-poor blood returning from the body. The finding, now published as a case report in Frontiers in Hematology, offers a rare window into one of the most diagnostically treacherous corners of cancer medicine: the intracardiac mass in a patient with newly diagnosed lymphoma.

The diagnostic journey began conventionally enough. Blood tests showed neutrophilic leukocytosis, mild anemia, and elevated platelet counts, with a white blood cell count of 15.95 × 10⁹ per liter and an erythrocyte sedimentation rate of 92 millimeters per hour. Ultrasound of the head and neck disclosed multiple enlarged, hypoechoic lymph nodes measuring up to three centimeters, some with irregular vascularization. An excisional lymph node biopsy settled the question of what was wrong: classical Hodgkin lymphoma, nodular sclerosis subtype. A staging PET-CT scan then mapped the disease to stage IIB, showing hypermetabolic lymphadenopathy above the diaphragm, but it also flagged something unexpected, a focal area of increased FDG uptake in the right pericardiac region that raised the possibility of cardiac or pericardial involvement by the lymphoma itself.

Before chemotherapy could begin, clinicians placed a peripherally inserted central catheter, a PICC line, to secure reliable venous access for the months of treatment ahead. Thirteen days later, a transthoracic echocardiogram performed as part of the pre-treatment assessment delivered a jolt: a 3.5 by 2.4 centimeter mass, lobulated and isoechoic, adherent to the lateral wall of the right atrium and extending toward the tricuspid valve plane. Critically, the mass was not obstructing venous inflow through the vena cava and had not compromised the patient’s hemodynamics. She felt nothing from it. An asymptomatic mass the size of a small plum, sitting inside the heart of a young woman about to start curative chemotherapy, presented her physicians with an urgent two-part question: was it tumor or thrombus, and how should it be treated?

The answer came from cardiac magnetic resonance imaging, the workhorse of modern tissue characterization. The CMR showed a right atrial mass with isointense signal on cine, T1-weighted, and T2-weighted sequences, internal signal heterogeneity, and, most tellingly, an absence of both first-pass perfusion and late gadolinium enhancement. In plain terms, the lesion had no blood supply of its own. Tumors, by contrast, are vascular structures that light up when contrast agent courses through them. An avascular, non-enhancing mass is the signature of a thrombus, a stationary clot, and the imaging team concluded that this was not lymphomatous infiltration of the heart but a floating clot anchored to the atrial wall.

Anticoagulation was started immediately, first with low-molecular-weight heparin at 6,000 international units daily, then escalated to full therapeutic dosing of 8,000 international units twice daily. Once specialists weighed the competing demands of clot control and chemotherapy compatibility, the regimen was transitioned to apixaban, a direct oral anticoagulant, at 5 milligrams twice daily, which the patient continues to take. The choice was not arbitrary. Doxorubicin, a cornerstone drug of the ABVD regimen used in Hodgkin lymphoma, can reduce the area under the curve of apixaban, potentially lowering its systemic exposure and weakening its anticoagulant effect. Sequencing the therapies, heparin first during the most intensive phase, apixaban later, allowed the team to navigate this pharmacological interaction safely.

The patient then received the HD17 regimen, two cycles of escalated BEACOPP followed by two cycles of ABVD, and completed the planned course without significant treatment-related or thrombotic complications. End-of-treatment PET-CT demonstrated a complete metabolic response, scored as Deauville 2, meaning no residual metabolically active lymphoma. A follow-up echocardiogram performed one month after treatment completion showed the right atrial mass had shrunk from 3.5 by 2.4 centimeters to 1.7 by 1.2 centimeters, still without any obstruction to venous inflow. The patient remains under surveillance with no relapse or other significant clinical events recorded.

What makes this case scientifically interesting is the timing. Venous thromboembolism is a well-recognized complication of hematologic malignancies, with reported incidence in lymphoma patients ranging from 4 to 10 percent, and rates as high as 1.5 to 13 percent in studies of lymphoma-associated thrombosis more broadly. But the overwhelming majority of these events occur during active chemotherapy or after placement of a central venous catheter. Thrombosis detected before any systemic treatment has begun is genuinely uncommon, and intracardiac thrombosis is rarer still. A review of the published literature on Hodgkin lymphoma turned up only a handful of comparable cases, and every one of them occurred during or after treatment, never at diagnosis.

The Padua team is careful about attribution. The 13-day interval between PICC placement and echocardiographic detection of the mass strongly suggests a catheter-related or catheter-contributed mechanism. Central venous catheters promote clot formation through several pathways: local endothelial injury during insertion, disturbed blood flow around the catheter tip, and activation of the coagulation cascade on the foreign-body surface. In a patient whose lymphoma had already pushed her into a hypercoagulable state, with elevated white cells, platelets, and inflammatory markers, these catheter effects may have found fertile ground. Yet the authors acknowledge a fundamental limitation: no cardiac imaging was performed before the PICC was inserted, so it is impossible to determine whether the thrombus was already present, partially formed, or entirely catheter-induced. The honest answer is that both malignancy-related hypercoagulability and the catheter likely contributed.

The case also underscores how easily such a finding can be misread. The focal FDG uptake on the staging PET-CT initially raised concern that the lymphoma had reached the heart or pericardium, a scenario that would have altered both staging and treatment. But detailed reassessment showed the uptake was not anatomically concordant with the interatrial mass seen on echocardiography, and the CMR findings pointed decisively toward thrombus rather than tumor. This distinction mattered enormously: anticoagulation is the right treatment for a clot but would be useless against lymphomatous tissue, while chemotherapy addresses the cancer but leaves a thrombus in place. Multimodality imaging, echocardiography for rapid detection and hemodynamic assessment, CMR for tissue characterization, and PET-CT for metabolic mapping, was what allowed the team to thread this needle correctly.

Management of right atrial thrombosis remains a matter of debate, with evidence drawn largely from case reports and small series rather than controlled trials. Options include systemic anticoagulation, thrombolysis, and surgical thrombectomy, selected according to thrombus size, mobility, hemodynamic compromise, and embolization risk. For clinically stable patients with cancer-associated thrombosis, guidelines from the American Society of Hematology recommend low-molecular-weight heparin or direct oral anticoagulants as first-line therapy, which is precisely the path this patient followed. Her outcome, complete lymphoma remission, a shrinking clot, and no thromboembolic or hemorrhagic events, illustrates what early recognition and coordinated hematologic, cardiological, and oncologic care can achieve. The broader lesson for clinicians is uncomfortable but clear: in newly diagnosed lymphoma patients, an incidental right atrial mass may be a clot, not cancer, and distinguishing between the two before starting treatment can change everything that follows.

Subject of Research: Right atrial thrombosis detected before treatment in a patient with newly diagnosed classical Hodgkin lymphoma

Article Title: Right atrial thrombus in treatment-naive patient with an early-stage classical Hodgkin lymphoma: a case report and review of the literature

Article References: Giordano, A., Bodanza, V., Angotzi, F., Cellini, A., Bevilacqua, A., D’Antiga, M., De Ferrari, M., Pergola, V., Campello, E., Trentin, L., & Visentin, A. (2026). Right atrial thrombus in treatment-naive patient with an early-stage classical Hodgkin lymphoma: a case report and review of the literature. Frontiers in Hematology, 5, Article 1874214. https://doi.org/10.3389/frhem.2026.1874214

Image Credits: AI Generated

DOI: 10.3389/frhem.2026.1874214

Keywords: Hodgkin lymphoma, right atrial thrombus, cancer-associated thrombosis, cardiac MRI, PET-CT, anticoagulation, apixaban, PICC line, venous thromboembolism, echocardiography, hematology, case report