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In colon cancer, extraosseous uptake of bone-seeking radionuclide in
liver metastases is commonly seen on the bone scan. However, extraosseous
deposition in lymph node metastasis is rare. The authors report a case in which
metastatic pulmonary lymph node metastases from colon cancer were shown to
contain concentrated Tc-99m methylene diphosphonate (MDP). Computed tomography
(CT) of the chest showed enlarged calcified lymph nodes at the bilateral hilar
regions, and should be considered for extraosseous Tc-99m MDP accumulation.
A 60-year-old female patient with descending colon cancer (mucinous
adenocarcinoma), status post chemotherapy, was referred for a scintigraphic
bone scan to evaluate for metastatic disease and assist in planning therapy.
The bone scan was performed at three hours after the injection of 740MBq (20
mCi) Tc-99m MDP. Findings include intense radiotracer accumulation in the
anterior aspect of the right 6th rib. Additionally, soft tissue uptake is noted
in bilateral pulmonary hilar regions (Figure 1a). Unenhanced CT of the chest
performed 10 days earlier demonstrated metastatic lymhadenopathy and enlarged
calcified lymph nodes at the bilateral hilar regions (Figure 1b). Postenhanced
CT demonstrated large metastases at the liver (Figure 1c). Although
accumulation of Tc-99m MDP in liver metastases with no apparent calcification
occurs frequently in colon cancer, no characteristic Tc-99m MDP uptake was observed
within those metastatic lesions.
Extraosseous uptake of Tc-99m MDP has been reported in various
pathologic conditions [1,2]. Mucin-producing tumors contain a glypoprotenin
that is biochemically similar to ossifying cartilage and binds calcium salts.
Classically, mucinous adenocarcinoma tumors of the gastoinestinal tract are
associated with this mechanism of Tc-99m MDP deposition in the primary and
metastatic tumors [3,4]. These findings mainly correspond in location to
extraosseous uptake on the bone scan, and suggest that the accumulation of
Tc-99m MDP in the present case is strongly related to the calcium deposition.
It also appears that Tc-99m MDP may accumulate in a calcified metastatic lesion
before the calcification appears on x-ray CT [5].
COMPETING
INTERESTS
The authors declare they have no conflict of interests in publishing
this case study.
ACKNOWLEDGMENTS
This work was supported by Research Grants MOST 103-2320-B-037-025 from
the Ministry of Science and Technology, KMU-TP105E12, KMU-TP105PR06,
KMU-M106029, 105KMUOR02 and KMU-O104003 (Aim for the Top 500 Universities
Grant) from Kaohsiung Medical University, and NSYSUKMU106-P011 from NSYSU-KMU
Research Project, Taiwan.
1. Tsai SC, Kao CH, Lin WY, Wang SJ. Intestinal
accumulation of Tc 99m MDP on bone scan. Semin Nucl Med 1999;29:80-81.
2. Takahashi T, Machida K, Honda
N, Hosono M, Oku S, Osada H, Murata O, Nishimura
K, Ohno H. Extraosseous accumulation of 99mTc-MDP in lymph node metastases
of small cell carcinoma of the esophagus. Annals of Nuclear Medicine
2004;18:157-160.
3. Freeman L, Zuckier L. Nonosseous,
nonurologic uptake on bone scintigraphy: atlas and analysis. Semin Nucl Med
2010;40:242-256.
4. Shepherd TM, Idakoji IA, Pampaloni MH.
Incidental Detection of Gastrointestinal Stromal Tumor by Tc-99m MDP Bone Scan.
Clin Nucl Med 2012;37:198-199.
5. Senda M, Tamaki N, Torizuka
K, Fujiwara Y, Kudo M, Tochio H, Ito H, Yamaguchi
H, Saiki Y, Ikekubo K. Accumulation of Tc-99m Methylene Diphosphonate
in Calcified Metastatic Lesions of the Liver from Colonic Carcinoma: Comparison
with Calcification on X-ray Computed Tomogram. Clin Nucl Med 1985;10:9-12.
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