British Journal of Radiology 74 (2001),378-381 © 2001 The British Institute of Radiology
Breast uptake of iodine-131 mimicking lung metastases in a thyroid cancer patient with a pituitary tumour
P-F Kao, MD, ScM
1
H-Y Chang, MD
2
M-F Tsai, MD
1
K-J Lin, MD
1
K-Y Tzen, MD, ScM
1 and
C-N Chang, MD
3
1 Department of Nuclear Medicine, Chang Gung Memorial Hospital and University, 5 Fu-Hsing Street, Kwei-Shan, Taoyuan
2 Division of Endocrinology, Department of Internal Medicine
3 Department of Neurosurgery, Chang Memorial Hospital, 199 Tung Hwa North Road, Taipei, Taiwan
in final form 11 December 2000
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Abstract
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We report a case of a 44-year-old female thyroid cancer patient with a pituitary tumour. 131I whole body scanning showed a change of chest uptake from a unilateral crescent uptake to a bilateral full breast uptake pattern. Hyperprolactinaemia and a pituitary tumour were diagnosed as a result of observing the 131I breast uptake.
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Introduction
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Radioiodine is taken up by the lactating breast [1, 2]. However, radioiodine uptake by the non-lactating breast has only recently been noted [3]. Breast uptake of radioiodine can be distinguished from thyroid cancer lung metastases by its characteristic appearance [4], for instance by obtaining posterior and/or lateral projections of the chest, or by observing a shift in the site of maximum concentration of radioiodine when the breast position is manually altered [3]. However, breast uptake may be misinterpreted as thyroid cancer lung metastasis if it occurs with an atypical pattern or is clinically unexpected.
We report a case of 131I breast uptake in a thyroid cancer patient who was subsequently found to have hyperprolactinaemia and a pituitary tumour. Different patterns of breast uptake of 131I helped to elucidate the underlying disease.
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Case report
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A 44-year-old female had a thyroidectomy for a papillary thyroid carcinoma 10 years ago. The patient had periodical whole body 131I scans and serum thyroglobulin measurements after the operation. Abnormal 131I activity in the right chest was first recognized with a 1110 MBq 131I whole body scan 3 years ago. At this time, a right lateral projection of the chest could not clearly differentiate between lung metastasis and breast uptake (Figure 1
). CT showed a tiny lesion, suspicious of a metastasis, over the right lower lung. Three therapeutic doses of 3700 MBq of 131I were given orally 6 months, 12 months, and 20 months later.
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Figure 1. (A) Anterior and (B) posterior views of the 131I whole body scan showing an irregular pattern of 131I uptake in the lower right chest region. Point sources indicate the skull vertex, shoulder and iliac crest levels, respectively. (C) The right lateral projection of the chest region shows 131I activity is anterior but could not clearly differentiate between breast and lung metastasis.
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The last 131I therapeutic whole body scan showed 131I uptake in the bilateral lower chest regions (Figure 2). Compared with the 131I whole body scans obtained 6 months and 12 months previously, the pattern of 131I uptake had now changed from an irregular pattern on the right side (Figure 1
) to a full bilateral breast uptake pattern in the lower chest (Figure 2). Serum thyroglobulin levels were all below 1 ng ml-1 during this period. Lateral images of the chest confirmed breast uptake of 131I (Figures 2C, D). A 201Tl whole body scan did not demonstrate any abnormal uptake in the chest region (Figure 3).
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Figure 2. (A) Anterior and (B) posterior projections of a later 131I whole body scan now show bilateral 131I uptake in the lower chest regions. (C) Right and (D) left lateral projections of the chest confirm the 131I activity is in the bilateral breast regions. Point sources indicate the skull vertex, shoulder and iliac crest levels, respectively.
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Figure 3. (A) The anterior and (B) posterior views of 201Tl whole body scan did not demonstrate any abnormal uptake in the chest and skull regions.
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On review it was ascertained that the patient had no clinical history of either galactorrhoea or mastitis, and had not breastfed during the past 10 years. However, the patient had had amenorrhoea for the past 4 years. The serum prolactin level waselevated (37.4–58.9 ng ml-1, normal 3.8–23.2 ng ml-1)
Chest CT and breast ultrasound examination were normal. CT of the pituitary fossa demonstrated a pituitary adenoma (Figure 4). The patient received bromocriptine treatment for 6 months. Owing to the tumour compressing the optic chiasma, surgery was performed through a transsphenoid approach to remove the pituitary adenoma. Histological examination of the tumour confirmed the diagnosis of a pituitary adenoma with apoplexy. The immunohistochemical stain was negative for prolactin and growth hormones. The serum prolactin level had dropped to 13.15 ng ml-1 within 3 months of the operation.
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Figure 4. Coronal image of the pituitary fossa on contrast enhanced CT shows a large, lobulated and generally enhancing lesion with a central low density, extending from the sella into the suprasellar and left parasellar regions.
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Discussion
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The mechanism of breast radioiodine accumulation remains unclear. Radioiodine is known to be excreted in breast milk [5–7], the production of which is regulated by prolactin [8]. Radioiodine breast uptake is therefore common in the early post-partum period and during lactation. Both conditions are associated with elevated prolactin levels. Radioiodine uptake in the chest field is therefore suspected as being owing to changes in the breast, rather than lung metastasis, if the patient is known to be breastfeeding [1, 2]. However, since this patient had no history of breastfeeding for the past 10 years, the elevated prolactin levels could not be related to the above-mentioned conditions.
Prolactin levels may also be raised by various drugs [9, 10] and by prolactinoma [11]. In addition, hypothyroidism, induced in preparation for radioiodine scanning and treatment, can be associated with galactorrhoea with or without hyperprolactinaemia [12, 13]. An occasional patient with thyroid cancer may therefore present with breast uptake on a radioiodine scan without a history of breastfeeding [3]. In this case, either hypothyroidism or a pituitary tumour may elevate the serum prolactin level. However, the serum prolactin level of this patient was measured during the thyroid hormone replacement period. We therefore concluded that the hyperprolactinaemia was being caused by a pituitary tumour.
Prolactin secreting pituitary adenomas commonly present with a marked elevation of serum prolactin, often more than 100 ng ml-1. Hypothalamic tumours and pituitary macroadenomas can compress the pituitary stalk, thus interrupting the transport of hypothalamic–pituitary factors resulting in hyperprolactinaemia [14]. The immunohistochemical stain of the pituitary tumour from this patient was negative for prolactin, indicating that the cause of the mild hyperprolactinaemia may have been the interruption in the transport of hypothalamic–pituitary factors [14]. The prolactin level of this patient returned to normal 2 weeks after surgical removal of the pituitary tumour.
Bakheet and Hammami [4] described four patterns of radioiodine uptake by the lactating breast. Radioiodine breast uptake may be misinterpreted as lung metastases when the uptake is irregular or unilateral [4], as in the first two studies. The patterns of breast uptake of 131I changed from a unilateral irregular uptake to a bilateral full breast uptake pattern in this case. The right and left lateral chest images aided thediagnosis of radioiodine breast uptake (Figures 2C, D). Although lung metastasis withnormal thyroglobulin levels has been reported [15, 16], combined chest lateral views and low serum thyroglobulin levels decreased the possibility of functional lung metastasis.
Thallium scintigraphy of breast lesions can be an effective means of differentiating benign from malignant lesions [17]. For example, the bilateral breast uptake of 201Tl in a nursing woman has been reported [18]. In this patient, there was no 201Tl uptake in the breast region to demonstrate any breast malignancy (Figure 3). The discrepancy between the 131I and 201Tl uptake in the chest region may help to confirm the diagnosis of non-malignant breast uptake of 131I.
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Acknowledgments
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The authors wish to thank Kathleen Ahrens, PhD for her help in preparing this manuscript.
Received for publication June 15, 2000.
Accepted for publication January 24, 2001.
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References
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Abstract
Introduction
