Resectable breast carcinoma with incidental benign-appearing lesion in the sacrum

A 63-year-old woman without significant personal past medical history presented to her primary physician with a one-month complaint of palpable right breast mass. The patient was referred to a breast surgeon for evaluation and underwent imaging studies that showed a 4 cm × 3 cm mass in the right upper outer quadrant. Core biopsy of the mass was performed and pathology revealed an invasive lobular carcinoma, classical type.

Family history was significant for breast cancer in a paternal aunt at the age of 35, and colon cancer in her paternal grandfather. She denied tobacco use, alcohol abuse or the use of illicit/IV drug use. Whole body PET/CT was performed and showed hypermetabolic activity in the upper outer quadrant of the right breast, as well as tiny sclerotic foci in the pelvis and spine that were too small to characterize.

Figure 1. PET/CT scan. Axial contrast-enhanced CT, PET, fused PET/CT and fused PET/CT with the corresponding SUV measurements (a) demonstrate a peripherally enhancing soft tissue mass with central lower attenuation in the upper outer quadrant of the right breast adjacent to the lateral margin of the pectoralis major muscle. Focal metabolic activity is associated with the lesion (maximum SUV up to 2.0). Coronal contrast-enhanced CT, PET, fused PET/CT and MIP PET images (b) demonstrate a round heterogeneously sclerotic 1.5 cm lesion in the superolateral left sacrum without focally increased metabolic activity. Courtesy of M Ghesani, MD

The differential diagnosis included bone islands vs. early osteoblastic metastatic disease. Follow-up evaluation by whole body nuclear medicine bone scan also showed focus of tracer uptake within the left superior sacrum in the same region of the sclerotic lesion without hypermetabolism on the PET/CT scan.

MRI of the sacrum revealed a benign appearing lesion in the left sacrum that appeared to be radiographically consistent with an enchondroma or fibrous dysplasia. A six-month follow-up was recommended to ensure stability, and the patient underwent right breast mastectomy with axillary lymph node dissection. She is awaiting consultation with medical oncology.

Discussion

Breast cancer is the second most common cause of cancer mortality in women and the main cause of death in women aged 40 to 59 years. The main sites of metastases are the lungs, liver, bone and brain. If systemic therapy is indicated, and if an endocrine response is based on immunohistochemical hormonal staining, endocrine therapy is the preferred first-line systemic treatment. Among women with lytic, and probably blastic, boney metastases, bisphosphonate therapy in combination with either endocrine therapy or chemotherapy prolongs the time to first skeletal complication and decreases the proportion of women who develop complications related to bone metastases. The challenge in treating women with metastatic breast cancer is to weigh the likelihood of achieving palliation with the available therapies against their potential adverse effects on the patient’s quality of life.

Figure 2. Whole body Technetium-99m-MDP bone scan. The mixed sclerotic lesion in the superior left sacrum demonstrates moderately increased focal tracer uptake. Photos courtesy of M. Ghesani, MD

The role of PET/CT in the staging evaluation of breast cancer is controversial. PET/CT does not add significant information over other imaging modalities for locoregional disease, either the primary site or axillary nodal status. The clinical benefit of routine PET/CT to detect occult distant metastatic disease is also uncertain.CT scan and radionuclide bone scans have a low diagnostic yield in women with early stage breast cancer and are not routinely necessary.

Fibrous dysplasia is a skeletal developmental anomaly of the bone-forming mesenchyme that manifests as a defect in osteoblastic differentiation and maturation. Almost any bone can be affected. Medullary bone is replaced by fibrous tissue, which appears radiolucent on radiographs with the classically described ground-glass appearance. Trabeculae of woven bone contain fluid-filled cysts that are embedded largely in collagenous fibrous matrix, which contributes to the generalized hazy appearance of the bone on imaging studies.

Figure 3. Noncontrast MRI. On axial and coronal T1-weighted images (a) and on sagittal T1-weighted images with and without fat suppression (b) the lesion is predominately hypointense with an irregular peripheral region of increased signal intensity. On T2-weighted images (c) the lesion is heterogenous with predominately low signal intensity along the inferior and lateral aspect corresponds to regions of increased density on the CT scan consistent with sclerotic calcifications. There is no surrounding marrow edema, and no evidence of osseous destruction. Courtesy of M Ghesani, MD

Enchondromas are common benign cartilaginous tumors that develop in the medulla. Although the vast majority of patients remain asymptomatic, clinical problems caused by enchondromas include skeletal deformity, limb-length discrepancy, and a small risk for malignant transformation. Malignant transformation in a solitary enchondroma is extremely rare (< 1%), but has been described in the past. When combined with a typical appearance on radiographs and an absence of pain, the diagnosis of enchondroma with MRI findings can be made with a high degree of confidence.

Amit Patel, MD, is a Fellow in Oncology at St Luke’s-Roosevelt Hospital Center.

Iwao Tanaka, MD, is a Resident in Radiology at St Luke’s-Roosevelt Hospital Center.

Sharon Rosenbaum-Smith, MD, is an Attending Breast Surgeon at St. Luke’s-Roosevelt Hospital Center.

Carlos Benitez, MD, is a Musculoskeletal Radiologist at St. Luke’s Roosevelt Hospital Center and Assistant Professor of Clinical Radiology at Columbia University, College of Physicians and Surgeons.

Munir Ghesani, MD, is an Attending Radiologist at St. Luke’s-Roosevelt Hospital Center and Associate Clinical Professor of Radiology at Columbia University College of Physicians and Surgeons.

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