Solitary sternal lesions in patients with cancer

A 64-year-old black man with a history of hepatitis C, a 40 pack-year smoking history and a family history of lung cancer presented with a two-to-three month history of gradually worsening dyspnea on exertion. This was associated with intermittent dry cough with one episode of hemoptysis, decreased appetite and about a 10-lb weight loss during the past two months.

About two years ago, he had undergone colonoscopy that showed a tubular adenoma with no other mass lesions. The CT scan of his chest showed mass-like consolidations in the bilateral lower lobes with an interval increase in the size and tissue density of the left lower lobe mass. The bilateral upper lobes also showed significant emphysematous changes with chronic volume loss in the right lower lung. There were no enlarged mediastinal lymph nodes.

The patient underwent flexible bronchoscopy, which showed no endobronchial lesions. The bronchial washings were negative for any malignant cells. A biopsy of the left lower lung lesion was performed because it was suspicious for malignancy based on his imaging studies. The final pathology showed mucinous type bronchoalveolar carcinoma. He is clinically stage IIb (T3N0M0), according to the new TNM classification.

The patient also complained of sternal tenderness; however, the chest X-ray did not show any bony lesion. A subsequent radionuclide bone scan using 25.2 mCi of Technetium-99m was performed. It showed a focus of moderately increased tracer uptake in the midsternum. This was further evaluated by reconstructed CT scan images that showed a cystic lesion with a possible adjacent fracture. Currently, the patient is being evaluated for possible surgical evaluation and systemic therapy for his lung cancer. The sternal lesion seen on bone scan is thought to be nonmalignant considering the imaging findings and the rarity of these lesions in primaries other than breast cancer.

Figure 1. Axial image from a noncontrast chest CT reveals a multilobular spiculated mass in the lateral left lower lobe that was present on an abdominal CT performed nine months prior.

Figure 2. Axial image from a noncontrast chest CT in bone windows reveals a cystic lesion in the sternum (magnification of the sternum). There were no other osseous lesions.

Figure 3. Reconstructed sagittal CT images demonstrate a fracture through the cystic sternal lesion.

Figure 4. A Technetium-99m MDP whole body bone scan, with a magnified view of the sternum, demonstrates a focus of moderately increased tracer uptake in the midsternum. There were no other suspicious foci of tracer uptake. Photos courtesy of M Ghesani, MD

Discussion

The presence of isolated sternal metastasis is rare, and most of the cases reported in the literature show it to be from primary breast cancer. Kwai et al did a retrospective analysis involving more than 1,100 breast cancer patients and found solitary sternal abnormalities in 34 patients (3.1%) on radionuclide bone scanning. Out of these, 76% (26 of 34) were found to have metastatic disease with sternal uptake of unknown etiology in another six lesions. Two of the lesions were thought to be related to degenerative disease, as evident on plain radiographs.

Sternal metastasis can remain solitary and confined to the sternum for a long time, as it does not have contact with the paravertebral venous plexus that accounts for most of the multicentric lesions seen with vertebral metastases. Another interesting observation by Kwai et al was the involvement of internal mammary lymph nodes in 71% of the patients with sternal metastases, suggesting a possible metastatic route from the primary breast tumor via these lymph nodes.

The isolated sternal lesions can be treated with a curative intent with involvement of mediastinal lymph nodes providing important prognostic information. Noguchi et al reported data on nine patients with breast cancer who were found to have solitary sternal metastasis. The survival correlated with the status of mediastinal and parasternal lymph nodes at surgical resection. All four patients with metastatic lymph node involvement died within 30 months, whereas three of five patients with no evidence of lymph node metastasis survived longer than six years.

However, these solitary sternal metastases are rare in other malignancies, with only a few cases reported in the literature so far. Horita et al have reported a patient with metastatic disease to the sternum. This patient presented with a chest wall mass extending from the sternum into the subcutaneous tissues. The resected specimen showed possible metastatic hepatocellular carcinoma, although the primary was never found, even after nine months follow-up. In 2007, Lequaglie et al reported a case of metastatic adenocarcinoma of the pancreas that presented with sternal pain and was found to have a solitary osteolytic lesion in the sternal manubrium. He underwent surgical resection, including mediastinal lymphadenectomy showing secondary adenocarcinoma with three metastatic lymph nodes.

Thus, the presence of solitary sternal lesions in patients other than breast cancer should be evaluated thoroughly because the evidence of metastatic lesions is rare. As seen in our case, the isolated sternal lesion seen on the initial bone scan was characterized as a possible cystic lesion adjacent to an old fracture. As seen from the reported literature, appropriate management of these lesions in cases of confirmed sternal metastasis has shown to improve DFS and OS. Therefore, we should be vigilant about these sternal lesions and they should be appropriately evaluated in the overall clinical context.

Sumit Talwar, MD, is a Fellow in Hematology and Oncology at St Luke’s-Roosevelt Medical Center.

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

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

For more information:

• Horita K. Journal of the Japanese Association for Thoracic Surgery. 1996;44:959-964.
• Kwai AH. J Nucl Med. 1988;29:324-328
• Lequaglie C. Chirurgia Italiana. 2007;59:901-905.
• Noguchi S. Cancer. 1988;62:1397-1401