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Advances in Radiotherapy
& Nuclear Medicine Symmetrical bilateral extranodal recurrence in FL

3. Discussion grade, viability, tumor cell fraction, proliferation, and
modulation of glucose metabolism or local perfusion.
FL represents the most common form of indolent lymphoma, For instance, grade 3 FL manifests heightened FDG
characterized by potential extranodal involvement affecting metabolism compared to other histologic subtypes. 11
various organs. 1,3,4 Extranodal sites, with or without nodal
involvement, typically encompass the head and neck, 3.2. Clinical implications and multidisciplinary
gastrointestinal tract, central nervous system, lungs, bones, approach
muscles, and skin. While muscle infiltration by lymphoma is Recent studies underscore F-FDG PET/CT as the gold
18
rare, it primarily manifests in the gluteal and pelvic muscles standard for detecting extranodal involvement, monitoring
and is often attributable to hematogenous or lymphatic post-therapeutic disease activity, and recommending it for
dissemination. Two discernible patterns of muscle involvement staging patients with potentially curative-intent FDG-avid
are discernible through imaging: diffuse infiltration with lymphomas. Although recognized for its utility in avid
12
muscle enlargement and focal intramuscular masses. 5 FDG lymphoma, this technique finds critical application
3.1. Advantages and limitations of imaging in indolent lymphomas like FL. In this case, the focal
18
modalities for diagnosis and staging and intense F-FDG uptake in the PET scan, although
symmetric, suggested extranodal disease relapse. 13
Accurate diagnosis, localization, and staging are paramount
6
for determining the optimal treatment strategy. CT with Given the findings, ultrasound was pursued to obtain
contrast enhancement typically serves as the frontline a clearer delineation of the lesions. Ultrasound revealed
imaging modality for lesion identification and extent hypoechoic polylobulate lesions distinctly demarcated
determination, according to Lugano classification. 7 in a “nodular focal” pattern with a vascularization signal
on the color-Doppler module. Ultrasound facilitated
14
Surov et al. elucidated various presentations of muscle targeted biopsy collection, as these superficial lesions are
lymphoma on CT, with contrast-free studies revealing focal challenging to define on CT examination.
or diffuse muscle swelling with irregular hypodense regions
and/or indistinct margins. Post-contrast administration Ultrasound examination enabled the definition of a
enables differentiation of contrasting enhancement grades, predominant deep muscle lesion with upper dermis sparing,
with descriptions including small rim-enhancing lesions and US-guided biopsy confirmed disease recurrence within
with central hypoattenuation. 8 less than 2 years of follicular B-cell lymphoma, warranting
patient referral for bone marrow transplantation.
Magnetic resonance imaging (MRI) serves as an
alternative imaging modality; however, its costliness and The peculiarity of our case is underscored not only
nonspecific characteristics in musculoskeletal lymphoma by the rare involvement of deep muscle but also by
may limit its utility. In recent years, F-FDG PET has lesions that are indistinguishable from adjacent tissues
9
18
emerged as a pivotal tool in lymphoma staging and therapy on CT examination, even after post-contrast agent
response assessment, attributable to its capacity to identify administration, potentially misleading even experienced
radiologists. However, CT remains the primary modality
metabolically active lesions. 7,10
for staging and follow-up, enabling the identification of
The effectiveness of 18 F-FDG PET/CT in staging lymphoadenomegaly and lesions, although with limitations
and restaging B and T-cell lymphomas and Hodgkin’s due to lesion characteristics. The F-FDG PET/CT scan
18
lymphoma primarily stems from its ability to detect FDG- proves invaluable for detecting and localizing rare instances
avid lymph nodes of normal size (<1 cm) and extranodal of lymphoma in muscles, providing a comprehensive
sites that are potentially undetectable on CT scans. In our examination of all body segments.
case, CT follow-up depicted solely symmetrical muscle 18
This case report underscores the pivotal role of F-FDG
enlargement at the thoracic-abdominal site without focal PET in specific scenarios where CT fails to provide adequate
contrast enhancement discernible to an inexperienced information. Furthermore, it emphasizes the significance
15
radiologist. Nonetheless, radiologists may encounter of accurate staging and restaging through diverse imaging
difficulty diagnosing disease recurrence solely based on modalities, necessitating a multidisciplinary approach to
these CT imaging characteristics.
ensure patients receive the most appropriate treatment.
The contrast-enhanced CT exhibits limited sensitivity Clinical management is contingent upon disease stage,
in detecting lymphomatous involvement of normal-sized symptoms, extent, and burden, with treatment modalities
lymph nodes, bone marrow, spleen, and extranodal tissues. including observation, anti-CD20 antibody therapy with
The intensity of FDG uptake in lymphoma is influenced or without chemotherapy, radiotherapy, or stem cell
by several factors, including histological characteristics, transplantation. 16

Volume 2 Issue 1 (2024) 3 https://doi.org/10.36922/arnm.2828