Case Author(s): Stephen Schmitter, M.D. and Tom R. Miller, M.D., Ph.D., 5/27/01 . Rating: #D2, #Q4

Diagnosis: Lactating Breasts, Spindle Cell Sarcoma

Brief history:

25 year-old woman with low back pain

Images:

Anterior FDG-PET Projection Image

View main image(pt) in a separate image viewer

View second image(pt). Coronal FDG-PET Images

View third image(pt). Coronal, Axial, and Sagittal FDG-PET Images Through the Regions of Interest

View fourth image(ct). Selected Axial Computed Tomographic Images of the Chest

Full history/Diagnosis is available below

Diagnosis: Lactating Breasts, Spindle Cell Sarcoma

Full history:

25 year-old woman who presented with a 2-year history of low back pain radiating to her legs. MRI performed at an outside hospital demonstrated a large left-sided soft tissue mass adjacent to the posterior superior iliac spine. Biopsy showed spindle-cell proliferation. FDG-PET is requested for staging. The patient is also 4 months post-partum and is breast feeding.

Radiopharmaceutical:

14.6 mCi of F-18 Fluorodeoxyglucose intravenously

Findings:

The FDG-PET images (main, second, and third images) demonstrate markedly increased uptake in both breasts as well as increased uptake in the left buttock region, with central decreased uptake. No other abnormal uptake to suggest metastatic disease is identified.

Axial CT images (fourth image) through the thorax demonstrate dense soft tissue in the breasts.

Discussion:

FDG-PET imaging is useful in the evaluation of intermediate and high-grade soft tissue sarcomas. In one report FDG-PET had a sensitivity of 91% and specificity of 88%. Local recurrence has been detected with a sensitivity of 88% and specificity of 92%. In addition, the SUV has been shown to correlate with tumor grade. The main differential considerations in this case, without knowing the clinical history, were sarcoma or abscess.

Intense uptake of FDG in lactating breasts has been described. Because the activity is diffuse and bilateral rather than focal, it is unlikely that it would be mistaken for a pathologic process, particularly if the interpreter of the images is aware of the patient's lactation status. Inflammatory breast cancer can cause diffuse FDG uptake, but it would be unusual for it to present bilaterally and symmetrically.

There are limited data regarding dosimetry to an infant due to breast-feeding when the mother underwent FDG-PET imaging. In this patient, minimal activity was found in the breast milk obtained using a breast pump. A 13.4 mL sample of right breast milk obtained at 100 minutes post-injection contained 10.0 nCi/mL/mCi injected decay corrected to the time of sampling. The total volume of this "feeding" represented 0.033% of the injected dose. A 12.4 mL sample of left breast milk obtained 115 minutes post-injection contained 11.2 nCi/mL/mCi injected decay corrected to the time of sampling. The total volume of this "feeding" represented 0.039% of the injected dose.

Thus, the main factor in dosimetry to the infant appears to be the close proximity of the infant to the mother during feeding rather than passage of FDG into breast milk.

References: Schwarzbach MH et al., Clinical value of (18-F) fluorodeoxyglucose positron emission tomography imaging in soft tissue sarcomas. Annals of Surgery. 231(3):380-6, 2000 Mar.

von Schulthess GK, ed. Clinical Positron Emission Tomography: Correlation with Morphological Cross-Sectional Imaging. Philadelphia: Lippincott Williams & Wilkins, 2000.

Followup:

Twelve days later, the patient underwent surgical resection of the mass, revealing spindle cell sarcoma, grade I/III.

ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Breast, Category:Metabolic, endocrine, toxic)

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Case number: pt060

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