Although [18F]FDG-PET has proven helpful in the diagnosis and therapy follow-up in patients with lymphoma, the specificity of [18F]FDG uptake has been brought into question because of its behaviour similar to glucose metabolism, which may indiscriminately increase in benign processes such as inflammation or infection [3-5].
Six percent (11/182) were found to be residual benign processes such as inflammation, fat necrosis, or FCC.
However, benign processes such as post-operative changes (Fig. 6) and endometriosis (Fig. 7) can be mass-like and mimic cancer.
Diagnosis of these lesions is challenging because the enhancement of normal tissues and some benign processes, such as fibrocystic change, might show similar appearances [ 12, 21, 38, 39].
We have found that benign processes, such as reactive hyperplasia, can cause regional node enlargement and FDG avidity on PET imaging in children with sarcomas (Fig. 6).
We have also found that benign processes, such as active infection, can result in substantial FDG uptake within pulmonary nodules, mimicking that seen in metastases (Fig. 3).
Sonographic examination of the thyroid can differentiate between micro-calcifications, which are highly associated with papillary thyroid carcinoma, and eggshell calcifications, which favour a benign process such as colloid cysts (Figs. 1 and 2) [4].
Malignant cells mostly show low levels of glucose-6-phosphatase compared with many normal tissues and benign pathological processes such as inflammation, leading to different kinetics of FDG accumulation between benign and malignant processes (Yamada et al, 1995; Lodge et al, 1999; Nakamoto et al, 2000).
COL11A1/procollagen 11A1 expression is mostly absent in benign inflammatory processes such as breast sclerosing adenosis [ 16, 54], chronic pancreatitis [ 41], and diverticulitis (our own observations; data not shown), and is rather low in familial adenomatosis polyposis adenomas [ 1, 2].
The differential diagnosis includes benign and malignant processes, such as aneurysmal bone cysts, fibrous dysplasia, non-ossifying fibroma, osteoid osteoma, eosinophilic granuloma, giant cell tumours, osteoblastoma and Ewing sarcoma [13].
Interestingly, inflammatory changes of the breast can range from benign self-limited processes such as puerperal mastitis, to highly aggressive malignant inflammatory carcinoma.
