99mTc-albumin nanocolloid scan was initially used in inflammatory bone disease studies and in areas of disease other than the abdomen; in consideration of its notably aspecific bone marrow uptake, this indication is considered as obsolete and 99mTc-labelled leukocyte or 18F-FDG PET are commonly used and nanocolloid scan is usually performed to rule out bone marrow surgical dissemination. Our purpose is to confirm that in selected cases nanocolloid scan still can be a useful tool to demonstrate a chronic flogosis.
We report two different cases of histiocyte-mediated flogosis showing, respectively, a partial mismatch between leukocyte and nanocolloid studies, with a higher nanocolloid uptake related to chronic flogistic pathology, and an extraosseous matched leukocyte and nanocolloid uptake.
Case 1: The patient was referred to our institution for tibial plateau fracture and was treated by osteosynthesis; 9 months later the patient experienced knee swelling and a fistula appeared on the anterior cutaneous surface of the knee. Leukocyte labeled scan (99mTc-esametazine) showed only a faint superficial subcutaneous activity. A nanocolloid scan was then performed (99mTc-albumin nanocolloid) showing a very high activity, completely surrounding a synthesis screw. The patient underwent surgical toilette and removal of the screw. Pathology exam showed a prevalence of macrophages and multinucleate giant cells as for to foreign body reaction.
Case 2: The patient underwent tibial valgus osteotomy and after 6 months underwent surgery to remove screws and plates due to infection. 18 months later a fluid collection near the anterior tibial proximal metaphysis was evident at an ultrasound (US) exam. Both 99mTc-leukocyte and 99mTc-nanocolloids scans were performed and similar images (4 hrs and 24 hrs leukocyte scan, 1 hr nanocolloid scan) were obtained, showing in the 1/3 proximal leg a discrete high activity soft tissue area, in accordance to the US report. Fine-needle aspiration cytology showed a mixed white cell presence, with a prevalence of neutrophils and macrophages, in accordance to a chronic flogistic pattern.
According to the high histiocyte uptake, 99mTc-nanocolloid scan may still be useful as a marker of inflammation in selected cases, whenever a granulomatous or chronic flogosis is suspected, and not only to rule out bone marrow surgical dissemination.