Not All That Shines on a PET Scan Is Cancer: A Silicone-Induced Granuloma Masquerading as Malignancy (2023)

Not All That Shines on a PET Scan Is Cancer: A Silicone-Induced Granuloma Masquerading as Malignancy (1)

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Clin Pract. 2021 Mar; 11(1): 8–12.

Published online 2020 Dec 29. doi:10.3390/clinpract11010003

PMCID: PMC7774518

PMID: 33599216

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Data Availability Statement


PET/CT scans are frequently used in the initial workup of suspicious lesions but not all that lights up on a PET is cancerous. We wish to discuss a case of silicone-induced granuloma mimicking malignancy and the role of other imaging modalities for further workup.

Keywords: siloconomas, radiology, malignancy, pet imaging, false positives

1. Introduction

In a newly suspected diagnosis of lung cancer, ultrasound, X-ray, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) all play key roles in treatment planning. PET imaging in particular is useful for staging and practical information regarding the location of a suspected cancer. This, combined with CT can add further anatomical identification for further planning in treatment management [1]. PET scans utilize fludeoxyglucose in order to help locate areas of potential malignancy [2]. Not all that lights up on a PET scan can or should be considered malignancy, and clinical context can become even more pertinent. Inflammatory cells, sarcoidosis, and other thoracic etiologies such as silicone-induced granuloma, can cause PET scans to light up, giving false positives [3,4,5]. This false positivity when searching for malignancy can cloud diagnosis and can delay treatment, especially when risk factors indicate a likelihood of cancer.

2. Case Presentation

Our patient is a 75-year-old female with history of hypertension, hyperlipidemia, depression, chronic pain syndrome, chronic obstructive pulmonary disease (COPD), former smoking for 58 pack-years, and breast implantation (cosmetic) over 20 years go. Her initial presenting symptoms were dyspnea with shortness of breath on exertion. Due to her extensive smoking history, she received a screening chest CT which revealed a spiculated left lung nodule with mediastinal adenopathy and Linguine Sign causing concern for intracapsular silicone implant rupture (Figure 1B–D). Due to concern for lung cancer, a subsequent PET scan identified significant uptake in the lesion seen on the CT with the left upper lobe with MAX SUV 6.3 and a smaller focus of opacity was noted in the right upper lobe with MAX SUV 2.7 (Figure 2). Along with this, there was hypermetabolic activity in the right breast also appreciated. At this point, there was concern for breast or, more likely, lung cancer.

Not All That Shines on a PET Scan Is Cancer: A Silicone-Induced Granuloma Masquerading as Malignancy (2)

(A) Mammogram demonstrating extracapsular rupture of the right breast, (B) mediastinal window chest CT demonstrating Linguine Sign of the left breast implant, (C) chest CT showing an 18 mm × 14 mm nodule in the right middle lobe causing concern for malignancy, and (D) the same image showing a 17 mm × 14 mm spiculated left lung nodule with concern for breast involvement.

Not All That Shines on a PET Scan Is Cancer: A Silicone-Induced Granuloma Masquerading as Malignancy (3)

PET/CT demonstrating increased uptake with multiple mediastinal lymph nodes with a nodule in the right middle lobe and a spiculated left lung nodule with concern for breast involvement: the black arrows point to areas of suspicion.

She was referred for a breast ultrasound, which showed extracapsular silicone implant rupture. A mammogram of the right breast was performed, which was also negative for malignancy although it did confirm extracapsular implant rupture and extruded silicone (Figure 1A). She was referred to pulmonology for further workup of the lung nodules with endobronchial ultrasound (EBUS). Biopsy of multiple mediastinal nodes showed histiocytosis with possible granuloma formation. A CT-guided biopsy of the left lung nodule demonstrated more non-caseating epithelioid granulomas. The patient was prescribed a short course of Prednisone with instructions to follow-up in 6 months with surveillance imaging.

3. Discussion

Silicone breast implants were utilized beginning in the 1960s [6]. The first reported cases in the literature of silicone granulomas were reported by Winer et al. in 1964 [7]. Granulomas from ruptured implants have been reported previously and have been shown to have a wide variety of acute and chronic symptoms [8]. There is still much speculation around the pathophysiology of silicon-induced granuloma of breast implant (SIGBIC). It occurs in approximately 27% of individuals who have a silicone breast implant [9]. These silicone particles are believed to cause an autoimmune response increasing T-cell activation. If there is migration of the particles into the lymph nodes, this can result in an adjuvant effect, leading to localized inflammation and granuloma formation [10,11]. Histology from SIGBIC consists of histiocytes, granulomatous infiltrations, and a mix of lymphocytes such as T-cells and B-cells [10]. This can be seen in Figure 3 with the mix of lymphocytes and granuloma formation along with asteroid bodies specific for granuloma. What makes certain cases harder to diagnose is the presence of spiculation seen on CTs. While not specific for breast cancer, it is clinically correlated with cancer and makes the diagnosis highly suspicious [12,13].

Not All That Shines on a PET Scan Is Cancer: A Silicone-Induced Granuloma Masquerading as Malignancy (4)

Non-caseating granuloma from a CT-guided biopsy of the left lung nodule showing an asteroid body (black arrow), a typical finding in granulomas.

Ali et al. presented the case of a 66-year-old female also with history of breast augmentation surgery found with lethargy, weight loss, and anorexia. CT imaging showed 2 suspicious pulmonary nodules, while a mammogram revealed a spiculated 4.1-cm mass. Malignancy was ruled out after Ultrasound (US-)guided biopsy showed silicone granulomas without any microcalcifications or breast tissue. [14] Grubstein et al. described two cases of siliconomas manifesting as multiple pulmonary nodules. In both cases, the masses showed significantly elevated Flourodeoxyglucose (FDG) uptake on the PET scan, but malignancy was eventually ruled out by biopsy [15]. Neither of these cases utilized a PET scan during workup. These cases highlight the variance of what an implant-induced silicone granuloma can present and their mimicry of cancer.

What makes our case uniquely challenging is that the patient was at high risk for lung malignancy because of the extensive smoking history coupled with her age. This case illustrates that findings on PET/CT do not necessarily indicate malignancy, especially in patients with a history of ruptured silicone breast implants. The literature supports that PET scans are not the optimal imaging modality if there is suspicion of silicone granulomas due to their high chance of false positives for malignancy. MRI is more useful in imaging for silicone-induced granuloma formation compared to mammography and US, even when there is no capsule rupture [16]. In conclusion, we recommend that, when working up siliconoma from ruptured breast implants in the context of possible malignancy, performing an MRI first would be more prudent even if a PET/CT is later warranted.

Author Contributions

K.V. participated in the literature review and manuscript editing; P.T.S. participated in the literature review and manuscript editing; D.J. participated in the literature review and manuscript editing; K.K. participated in the literature review and manuscript editing. All authors have read and agreed to the published version of the manuscript.


The authors received no funding in the creation of this manuscript.

Institutional Review Board Statement

Ethical review and approval were waived for this study as our Institution did not believe such approval was necessary in this case.

Informed Consent Statement

Written informed consent was obtained from the subject involved in this study.

Data Availability Statement

The data presented in this study are available on request from the corresponding author. The data are not publicly available in order to protect patient information and confidentiality.

Conflicts of Interest

The authors have no conflict of interest to declare.


Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.


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Do granulomas light up on PET scan? ›

Inflammatory cells, sarcoidosis, and other thoracic etiologies such as silicone-induced granuloma, can cause PET scans to light up, giving false positives [3,4,5].

What cancers don't show up on PET scan? ›

Though most cancers are picked up on PET CT, there are a few which do not. The most important of these would be cancer of stomach (signet cell type). In such cases performing this test would be waste. However, there are cancers which are very sensitively detected which include lymphoma, GIST, etc.

Is cancer the only thing that shows up on a PET scan? ›

A PET scan is an effective way to help identify a variety of conditions, including cancer, heart disease and brain disorders. Your doctor can use this information to help diagnose, monitor or treat your condition.

Can a PET scan tell if a tumor is malignant? ›

PET imaging can be useful to determine whether a tumor is malignant (cancerous) or benign (not cancerous). Unlike other imaging tests like CT or MRI that show anatomy, the PET scan looks at the physiological changes and cellular activity, so cancer may be diagnosed much earlier.

Should I be worried about a granuloma? ›

Although granulomas may appear cancerous, they are not — they are benign. Occasionally, however, granulomas are found in people who also have particular cancers, such as skin lymphomas. So it is important to consult a doctor if you notice persistent lumps on your skin or have other symptoms of illness.

What is a silicone granuloma? ›

Silicone granulomas are firm, erythematous masses in the skin and subcutaneous tissues due to inflammatory reactions around particles of liquid silicone.

Can a PET scan tell if a tumor is malignant or benign? ›

A PET/CT scan can be more sensitive than other imaging tests and may find cancer sooner than other tests do. Not all tumors take up the radiotracer, but PET/CT is highly accurate in differentiating from the benign and malignant tumors it finds, particularly in some cancers such as lung and musculoskeletal tumors.

How often are PET scans wrong? ›

False positive results are commonly observed in areas of active inflammation or infection (Gupta et al., 20000), with a reported false positive rate of 13% and false negative rate of 9% (Alavi et al., 2002).

Do PET scans show cancerous lymph nodes? ›

A PET scan can show whether this tissue is active cancer or not. PET scans are sometimes used to look for cancer in the lymph nodes in the centre of the chest.

Do benign lung nodules light up on PET scan? ›

If the nodule does not change during that time, it is likely benign and needs no further treatment. Positron emission tomography (PET) scan: The PET scan will light up the nodule if it is rapidly growing or active. The brighter the nodule appears on the PET scan, the more likely that it is cancer.

What is the best scan to detect cancer? ›

A CT scan (also known as a computed tomography scan, CAT scan, and spiral or helical CT) can help doctors find cancer and show things like a tumor's shape and size. CT scans are most often an outpatient procedure.

Is a PET scan better than a biopsy? ›

Compared with CT-guided percutaneous bone biopsy, PET/CT-guided percutaneous bone biopsy is an effective and safe alternative with high diagnostic performance in the evaluation of hypermetabolic bone lesions to diagnose bone tumors and tumor-like lesions.

Does scar tissue light up on a PET scan? ›

Often, scar tissue at the site of surgical resection or radiation treatment may appear as an abnormality on the CT scan. The PET portion of the PET/CT scan can detect residual disease within the scar tissue and indicate if the treatment was successful, or if the tumor has returned.

What does it mean when a nodule lights up on a PET scan? ›

Positron emission tomography (PET) scan: The PET scan will light up the nodule if it is rapidly growing or active. The brighter the nodule appears on the PET scan, the more likely that it is cancer. The PET scan also looks at the rest of the body and can identify if the cancer has spread.

What can give a false positive on a PET scan? ›

Infection is one of the most common causes of false-positive 18F-FDG PET-CT findings post-chemotherapy. Chemotherapy patients are susceptible to a wide variety of infections, including upper respiratory chest infections, pneumonia, colitis and cholecystitis.

Are granulomas visible? ›

For example, if you're having a routine chest X-ray or CT scan because of a respiratory problem, your doctor may discover small spots on your lungs that turn out to be granulomas. If they're calcified, they're especially easy to see on an X-ray.


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