Breast imagingCase Type
Alessandro Marcucci 1, Chiara Boccaccio1, Ilaria Caramella2Patient
64 years, female
An incidental focal hypercaptation area on 18F-FDG PET/CT was reported in the left mammary gland of a 64-years-old female in follow-up for pulmonary adenocarcinoma and left pleural mesothelioma treated with surgery and chemotherapy. The patient has a history of left breast cancer treated with surgery and hormone therapy.
The 18F-FDG PET/CT exam was carried out after glycemic control (95 mg/ml), hydration of the patient, and image acquisition performed 63 minutes after administration of the radiocompound. The whole body 3D PET dataset was corrected for compensating the tissue attenuation by means of a low-dose unenhanced CT. PET show a small hypercaptation area of the superior internal quadrant of the left mammary gland (figure 1a, SUV max 2.5), corresponding to a subcutaneous elongated hyperdense abnormality on the correspondent CT images (figure 1b). The fusion image is shown in figure 1c. The same lesion was retrospectively visible on a CT exam performed eight months before (figure 2).
The physical examination allowed to correlate the area with a black hard subcutaneous micronodule that was seen close to the site of left inferior internal quadrantectomy. The lesion is most likely to attribute to the effect of a granulomatous inflammatory response to the charcoal residue of the previous injection for preoperative localisation.
The area is also visible on mammography with digital breast tomosynthesis as a small nodular opacity with clear margins and a benign appearance unchanged from the previous examinations (figures 3a,3b,3c) within the context of a fibrous and fatty A pattern as defined by BI-RADS .
Finally, ultrasound allowed to confirm the benign nature of the lesion (figure 4).
An isolated locoregional recurrence (ILRR) represents the reappearance of breast cancer in the region of the ipsilateral breast/chest wall or the draining regional lymph node basins. The majority are isolated first-failure events, with the remainder accompanying or following distant metastases. Charcoal marking for breast lesion has increased in the last decade, especially in non-palpable lesions and/or the ones that are difficult to reach with biopsy needles or surgical access. 
Most ILRRs are detected on physical exam or by routine mammographic or MRI surveillance. The physical exam may detect skin changes, palpable masses, or lymphadenopathy.  However, recurrence might be asymptomatic and detected at FU imaging with mammography, ultrasound, MRI, CT and 18F-FDG PET/CT. It is not rare to encounter an incidental finding of an 18F-FDG PET/CT–positive lesion in oncologic imaging. 
ILRRs occurring in another quadrant or exhibiting different histology may represent a new primary tumour rather than a true recurrence. 
Dedicated breast imaging, including mammography, ultrasound, and breast MRI, is the mainstay of evaluation of breast lesions. Mammography combined with tomosynthesis has a better cancer detection rate than mammography alone. Ultrasound is the most commonly used modality for supplemental imaging, particularly in women with dense breasts. ,
18F-FDG PET/CT suffers from low specificity within the breast, since inflammatory processes such as post-surgical changes, fat necrosis, granulomatous processes, and infections, may cause FDG hypercaptation. Benign tumours like fibroadenomas may be FDG avid. [4, 5]
Recently, charcoal granuloma mimicking malignant lesions has emerged as a possible diagnosis on imaging studies (mammography, ultrasound, and breast MRI) in some postoperative patients or in a conservative follow-up. 
ILRRs are associated with an unequivocal high risk of developing distant metastases and, consequently, poor survival.  The diagnosis of benign nature based on conventional breast imaging modalities may avoid unnecessary alarm and ulterior examinations, such as biopsy.
18F-FDG PET/CT positive breast lesions may be misinterpreted as ILRRs in women with treated breast cancer. To establish the nature of the lesions it is fundamental to correlate them with conventional breast imaging modalities.  False-positive charcoal granuloma should be suspected among different inflammatory processes on 18F-FDG PET/CT imaging in patients who previously performed preoperative charcoal marking.
Written informed patient consent for publication has been obtained.
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