CASE REPORT 
Annals of Nuclear Medicine Vol. 13, No. 4, 269-271, 1999 
Axillary lymph node uptake of Tc-99m MIBI resulting from extravasation should not be misinterpretated as metastasis 
Wei-Jen SHIH,* Jian-Kui HAN,** John COUPAL,* Becky WIERZBINSKI,* Sylvia MAGOUN* and Kelly GROSS* 
*Nuclear Medicine Service, VA Medical Center, and Nuclear Medicine Section, Department of Diagnostic Radiology, University of Kentucky Medical Center, Lexington, Kentucky, USA **Department of Nuclear Medicine, Shangton Medical University, Jinan, Shangton, China 
Ipsilateral axillary lymph node visualization due to extravasation of Tc-99m MDP intravenous injection has been well documented. A patient with suspected angina underwent Tc-99m MIBI myocardial SPECT who had extravasation of Tc-99m MIBI in the antecubital region resulting in ipsilateral axillary lymph node uptake. This finding should not be misinterpreted as lymphatic nodal metastasis in a patient with breast cancer or lung cancer. 
Key words: Tc-99m MIBI, axillary lymph node, lymphatic channel, lymphatic nodal metastasis 
INTRODUCTION 
IPSILATERAL AXILLARY or elbow visualization of the lymph node after infiltration of Tc-99m MDP or Tc-99m HMDP into the antecubital or wrist region has been reported.1,2 The molecular weight of the bone imaging agent Tc-99m HMDP is 512.99 which is also close to the molecular weight of Tc-99m MIBI, 777.96. Accordingly axillary lymph node in extravasation of Tc-99m MIBI may be observed. We present such a case of axillary lymph node visualization in a patient with antecubitally subcutaneous infiltration of Tc-99m MIBI. 
A CASE REPORT 
A 59-year-old man was referred for Tc-99m MIBI myocardial SPECT because of suspected angina. After iv injection of 1.221 GBq (33 mCi) Tc-99m MIBI imaging; anterior neck and thoracic images at thirty minutes showed a large area of increased uptake in the antecubital area resulting from infiltration, radiated lymphatic channels surrounding the hot area in the antecubital region and lymphatic channel toward to the axillary region, a focal area of increased uptake in the left axilla, and normal 

Received November 30, 1998, revision accepted April 1, 1999. 
For reprint contact: Wei-Jen Shih, M.D., Nuclear Medicine Service, VA Medical Center, Lexington, KY 40511, USA. 

uptake in the salivary gland, thyroid gland, lungs, heart, and the liver (Fig. 1). The two hours post-injection image showed persistent visualization of lymphatic channels toward the axillary region from the extravasation site, visualization of the axillary lymph node, and cardiac activity (Fig. 2). The results of myocardial SPECT concluded fixed hypoperfusion in the inferior wall of the left ventricle. After the Tc-99m MIBI myocardial SPECT this patient was followed-up for 6 months, he had not been found any malignancy including in the lung. 
DISCUSSION 
Incidental axillary lymph node visualization after radiotracer subcutaneous infiltration of bone imaging agent into the antecubital region has been well documented. 1,3-5 Ipsilateral visualization of the lymph node in the elbow after infiltration Tc-99m HMDP into the wrist region has been reported.2 Although this is infrequently seen in bone imaging agent uptake in the axillary lymph node, approximately 2% of axillary lymph node uptake has been visualized on bone scintigraphy,1 Tc-99m MIBI uptake in axillary lymph node in extravasation of the radiopharmaceutical has not been reported. 
Tc-99m MIBI, a lipophilic cationic complex, is widely used as a myocardial perfusion agent; like Tl-201 chloride, which is used as a tumor imaging agent, Tc-99m MIBI, also has shown ability in the detection of various tumors.6-8 Lymph node uptake in a patient with osteosarcoma,7 lung cancer 9,10 melanoma,11 thyroid cancer,12 and breast cancer8,13-16, has been reported. Among these, uptake by lymph node(s) in breast cancer patients is almost always in the axillary region 8,13-16 In lung cancer patients, in addition to mediastinal lymph node uptake,9,10 the axillary lymph node localization of Tc-99m MIBI is possible. Thus axillary uptake in the extravasation of Tc-99m MIBI should be carefully distinguished from lymphatic metastasis in the patients who have primary breast cancer or lung cancer. Keys for scintigraphic differentiation of lymphatic uptake due to extravasation from lymphatic metastasis include the apparent extravasation site in the antecubital area ipsilaterally and identification of lymphatic channels toward axilla as shown in Figure 1 and Figure 2. 
Another condition that might lead to misinterpretation of axillary lymph node uptake originated from malignancy and/or extravasation of the radiopharmaceutical is an accumulation of Tc-99m MIBI in the sweat glands. Although the mechanism of this localization is unknown, 46% of hyperparathyroidism patients' sweat glands were observed.17 In this condition the axillary uptake is diffuse rather than focal, and usually symmetrical. 
In summary, such visualization of the lymphatic channels as well as lymph node in our patient, whether Tc-99m MIBI can be utilize as lymphoscitigraphic agent should be further evaluation. Nevertheless, three probabilities explaining for an abnormal Tc-99m MIBI axillary uptake include lymphatic metastasis in breast cancer patients and possibly lung cancer patients, axillary sweat gland uptake, and axillary uptake due to extravasation of the radiopharmaceutical. Extravasation of Tc-99m MIBI always resulted in ipsilateral axillary uptake. The sweat gland accumulation of the agent usually is characterized by a diffuse uptake and symmetry on both axillae. For lymphatic metastastic disease, the areas of lymphatic uptake may be multiple and/or bilateral; however, there are often solitary lymph node metastasis. 
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