Occult Cardiac Metastasis in Asymptomatic Recurrent Leiomyosarcoma Documented on FDG PET/CT Scan

INTRODUCTION

Leiomyosarcoma (LMS) represents approximately 10–20% of soft tissue sarcomas and is characterised by a high propensity for local recurrence and hematogenous dissemination, particularly to the lungs, liver, and bones.^[1] Cardiac metastases from LMS are exceedingly rare, with only isolated cases reported in the literature, often detected post-mortem or incidentally during imaging. Clinical detection is challenging due to the absence of specific cardiac symptoms, making imaging modalities such as ¹⁸F-FDG PET/CT critical in identifying these metastases.

CASE REPORT

A 45-year-old male was diagnosed with leiomyosarcoma of the left thigh and underwent wide local excision followed by adjuvant radiotherapy. He developed local recurrence involving skin, subcutaneous tissue, and muscle 18 months later. PET/CT confirmed recurrence, and he underwent a second wide excision with negative margins and free flap reconstruction. Histopathology confirmed recurrence of LMS. He was started on adjuvant chemotherapy with Ifosfamide and Adriamycin. Due to haematological toxicity, doses were reduced from the fourth cycle onwards. Despite five cycles, surveillance PET/CT revealed new lung metastases confirmed by fine needle aspiration cytology (FNAC). He was subsequently treated with gemcitabine and docetaxel for eight cycles, achieving a partial response initially, followed by progression. A restaging FDG PET/CT scan revealed interval progression of a left lung mass and new FDG-avid lesions in the paravertebral region in cervical vertebra, right gluteal muscle, and notably a previously unseen soft tissue mass in the right ventricle abutting the interventricular septum, suspicious for cardiac metastasis shown in Fig 1. Echocardiography confirmed cardiac mass, clinical high suspicion did not warrant further tissue correlation due to procedure related complications. Given disease progression on two prior chemotherapy regimens, he was initiated on trabectedin.^[2]

Close

Fig 1: (A) Maximum intensity projection (MIP) of ¹⁸F-FDG PET/CT scan of leiomyosarcoma showing multiple FDG-avid metastases (blue and red arrows). (B and C) Coronal CT and fusion images show soft tissue lesion (red arrows) in right ventricle [upper row]; soft tissue metastasis in right dorsal paravertebral muscles (green arrows) [middle row]; soft tissue necrotic mass in left upper lobe of lung (blue arrows) [lower row]. FDG: Fluorodeoxyglucose; PET/CT: Positron emission tomography/computed tomography; CT: Computed tomography

Export to PPT

DISCUSSION

This case demonstrates an uncommon but clinically significant site of metastasis in leiomyosarcoma. Cardiac metastases from soft tissue sarcomas are infrequently diagnosed ante-mortem, with a reported incidence of 1.23% to 20% in autopsy studies, depending on tumour type and patient population.^[3,4] LMS shows a predilection for hematogenous spread; however, myocardial or endocardial involvement is rare, often incidentally detected on imaging. In the present case, cardiac metastasis was asymptomatic and detected only during routine FDG PET/CT surveillance. The right ventricular lesion was metabolically active, abutting the interventricular septum, with a potential for conduction abnormalities or obstructive physiology had it progressed undetected.

FDG PET/CT provides functional imaging that complements anatomical modalities, allowing for early detection of metabolically active lesions with high lesion contrast. It has demonstrated utility in soft tissue sarcoma staging, restaging, and monitoring response to therapy.^[5] In our case, FDG PET/CT was instrumental in identifying an occult metastatic lesion in the heart, highlighting its superior sensitivity compared to conventional imaging, especially when clinical suspicion is low.

Reports of cardiac metastasis from LMS are sparse in the literature, underlining the rarity of the incidence. Metser et al. described the PET/CT characteristics of equivocal soft tissue sarcoma metastases across various sites.^[6] Dencker et al. reported a similar case of cardiac metastasis in the right intraventricular space in uterine LMS, also detected by PET/CT.^[7] The role of hybrid imaging in evaluating atypical metastases and guiding treatment decisions is well known.^[8] Close clinical monitoring and imaging with echocardiography and cardiac MRI may potentially further delineate the lesion’s extent and impact. Cardiac metastases typically signify advanced disease with a guarded prognosis. Early detection, however, allows for anticipatory management of complications such as arrhythmias, cardiac failure, or embolisation. Incorporating cardiac assessment in routine imaging for patients with advanced sarcoma, especially with high metastatic burden, could be considered.

CONCLUSION

This case highlights a rare but critical manifestation of recurrent LMS with cardiac metastasis identified by FDG PET/CT. The use of advanced imaging enabled timely recognition of this lesion, influencing therapeutic planning and highlighting the importance of comprehensive restaging in aggressive sarcomas. Awareness and high suspicion for atypical metastases are essential in managing such complex cases, where early detection can improve clinical outcomes and patient quality of life.