Primary chest wall chondrosarcoma presenting as a breast mass

Chondrosarcomas are rare malignant neoplasms of chondroid matrix that commonly present with pain or as a palpable mass. When chondrosarcomas affect the rib, it is possible that patients present with a growing breast mass, although this has not been frequently reported. We present the case of a 46-year-old female complaining of an enlarging painless palpable mass of the right breast, which was diagnosed as chondrosarcoma after radiographic and pathologic workup. To our knowledge, primary chest wall chondrosarcomas presenting as a breast mass seen on mammogram has not been reported to date. It is important for radiologists to understand the imaging findings of chondrosarcoma, as these rare tumors can present in many ways. Correspondence to: Margaret Cookson, Herbert Wertheim College of Medicine, Florida International University, Miami Fl, USA; E-mail: margaret.t.cookson@ gmail.com


Introduction
Chondrosarcoma is a malignant neoplasm that produces a chondroid matrix with primary chondrosarcomas arising de novo and secondary chondrosarcomas developing in pre-existing benign lesions [1,2]. Chondrosarcomas are the most common malignant chest wall tumors [3] and third most common primary bone malignancy following multiple myeloma and osteosarcoma [4]. Despite an incidence of less than 0.5 cases per million people per year, chondrosarcoma is the most frequent malignant tumor of the thoracic cage [5]. While most primary chest wall chondrosarcomas are thought to arise de novo, as many as 10% are contributed to radiation exposure from treatment of previous malignancies, including breast cancer and lymphoma [6,7]. We present the case of a 46-year-old female presenting with an enlarging painless palpable mass of the right breast that was diagnosed as a chondrosarcoma after workup.

Case report
A 46-year-old female with no personal or family history of cancer presented with a painless palpable mass of the right breast, which she stated had progressively increased in size over the last three years. Physical examination revealed a firm, immobile, deep seated, grossly visible mass over the right breast measuring approximately 15 x 15 cm. There was no associated tenderness, discoloration or retraction of the overlying skin ( Figure 1).
Digital diagnostic mammography demonstrated a retropectoral right breast mass with central calcifications in an arc and ring configuration ( Figure 2). Ultrasound revealed a 16 cm heterogenous cystic and solid mass ( Figure 3). Ultrasound guided core needle biopsy was performed. Microscopic examination of the slides demonstrated large amounts of chondroid matrix with areas of myxoid changes. The chondrocytes demonstrate mild nuclear pleomorphism with rare mitoses, occasional multinucleated forms are also available, areas of cluster formation by chondrocytes some of which appear to be swollen as a result of cytoplasmic vacuolization. As per the pathologic findings described above this tumor is considered a grade 2, conventional chondrosarcoma ( Figure 4). CT was then obtained to define the extent of the tumor for preoperative planning and revealed a multilobulated septate 15 x 14.5 x 10 cm mass with several central scattered punctate mineralization's arising from the anterolateral segment of the right fifth rib ( Figure 5). MRI showed a large lobular T2 hyperintense mass arising from the anterior aspect of the right fifth rib invading the overlying pectoralis major muscle. Extension through the intercostal muscles into the anterior chest wall between the second through sixth ribs was also noted. Postcontrast MRI images demonstrated extensive septal enhancement, consistent with underlying chondroid matrix ( Figure 6).
The patient was referred for surgical management and successfully underwent a right mastectomy and right radical chest wall resection of the 3rd through 6th ribs with negative resection margins. On final pathology the tumor was found to arise from the surface of the costal cartilages and adjacent ribs and was found to invade the medullary cavity of the fifth rib. No lymph node or vascular invasion was identified. The tumor was confined by the pectoralis muscle with no invasion of the overlying mammary parenchyma. An incidental finding of DCIS intermediate nuclear grade DIN 2 was found in the lower outer quadrant of the right mastectomy specimen. The DCIS was greater than 1 cm from the closest parenchymal resection margin. No invasive component was identified.

Clinical and imaging findings
Conventional primary chondrosarcomas commonly present as pain or a palpable soft tissue mass in the 4th and 5th decade of life and demonstrate a slight male predominance [2,3]. They frequently present in long tubular bones, most commonly in the femur with the rib

Etiology
The majority of primary chest wall chondrosarcomas arise de novo. However, approximately 10% of the tumors are thought to be radiationinduced after treatment of other malignancies. Secondary chondrosarcomas can develop in pre-existing benign lesions.

Incidence
The incidence of a conventional primary chondrosarcoma is less than 0.5 cases per million people per year. However, it is the most frequent malignant tumor of the thoracic cage.
Gender Ratio Primary chondrosarcomas have a slight predilection for males.

Age Predilection
Primary chondrosarcomas typically present in the fourth and fifth decades of life.

Risk Factors
Risk factors that have been identified with developing primary chest wall tumors include prior trauma and radiation treatment for other malignancies, including breast cancer or lymphoma.

Treatment
Surgical resection is the most effective treatment, as primary chest wall chondrosarcomas are resistant to chemotherapy and radiotherapy.

Prognosis
Prognosis and survival rate are contingent upon histologic grading, which is based upon tumor mitotic rate, cellularity, and nuclear size. The fiveyear survival rate for grade 1 tumors is 90%, grade 2 tumors is 81% and grade 3 tumors is 43%. The ten year survival rates are 83%, 64%, and 29% for grades 1, 2, and 3 tumors, respectively.

Image Findings
When presenting in a female, primary chest wall chondrosarcoma may be demonstrated on mammogram as a retropectoral mass with central calcifications in an arc and ring configuration. Ultrasound will reveal a cystic and solid nonvascular mass. CT imaging will demonstrate a multilobulated septated mass with several central scattered punctate mineralizations. T2 MRI will show a lobular hyperintense mass. Postcontrast MRI images will demonstrate septal enhancement.  accounting for 8% of all cases. They typically arise at the costochondral junction of the anterior portion of the rib [6].
Chondrosarcomas present radiographically with cartilaginous calcifications or scalloping [8]. Both benign and malignant lesions are characterized by "arc and ring" calcifications. Radiographic features that point to a malignant origin include lobulations, cortical destruction, size greater than 5 cm, and tumor location in the axial skeleton [2,9]. On CT, chondrosarcoma is characterized by ring and arc chondroid matrix mineralization. Features such as soft-tissue extension, lytic patterns, endosteal scalloping, amorphous, irregular, punctate or irregular calcifications scattered within the lesion [6,10,11] are consistent with high grade tumors. On MRI, chondrosarcoma appears as a heterogeneous mass with intermediate signal on T1-weighted sequences and hyperintense signal on T2-weighted sequences [12]. In our case, given the classic ring and arc type internal calcifications seen on mammography, the leading diagnosis was chondrosarcoma which was confirmed via ultrasound guided core needle biopsy.

Differential diagnoses
Chondrosarcoma should be included in the differential diagnosis for patients who present with an enlarging painless palpable breast mass that has retropectoral central ring and arc type calcifications on initial imaging, including mammography. These radiographic findings can be nonspecific when initially noted, but consideration should be given to a primary chondrosarcoma when presenting as an enlarging firm immobile mass. The patient's age and tumor location can help differentiate chondrosarcoma from other differential considerations. The main differential diagnoses include but are not limited to osteosarcoma, enchondroma, and osteochondroma. Further considerations before pathologic correlation included chest wall lymphoma, multiple myeloma and fibromatosis.

Osteosarcoma
Osteosarcomas are malignant bone forming tumors that, like chondrosarcomas, present with soft-tissue mass or swelling. Unlike chondrosarcomas, they typically present before the age of 20, as bone growth is greatest in adolescence. They tend to occur in the metaphysis of long bones, with up to 60% occurring at the knee. Like chondrosarcomas, osteosarcomas demonstrate ring and arc calcifications, a soft tissue mass, and aggressive periosteal reactions on plain radiograph. However, a sunburst periosteal reaction is more typical for osteosarcoma.

Enchondroma
Enchondromas are benign bone lesions that are typically diagnosed in childhood and adolescence. Unlike chondrosarcomas, enchondromas are usually incidental findings on imaging and are asymptomatic. They have a predilection for the medullary cavity of tubular bones and up to 50% of them occur in the hands and feet. Very rarely, they can transform into a malignant low-grade chondrosarcoma. Like chondrosarcomas, enchondromas are characterized by chondroid ring and arc calcifications on imaging. However, enchondromas exhibit benign features: a well circumscribed lobulated mass with sharply defined margins and no cortical remodeling or periosteal reactions.

Osteochondroma
Osteochondromas are benign bone tumors that typically develop during childhood, although they can present at any age. They are either found incidentally on imaging or can present with a palpable mass or mechanical impingement on nerves or vasculature due to size. Osteochondromas typically arise in the appendicular skeleton. Like other differentials for chondrosarcoma, osteochondroma is characterized by ring and arc calcifications on plain radiographs. There is no bony destruction or soft tissue expansion, helping to differentiate it with a chondrosarcoma. These tumors can be pedunculated and can broaden the bone metaphysis from which they originate.

Treatment and prognosis
Surgical resection is the most effective treatment as chondrosarcoma grows slowly and is relatively resistant to chemotherapy and radiotherapy [1,3,[13][14][15]. Prognosis and survival rate are contingent upon histologic grading, which is based upon tumor mitotic rate, cellularity, and nuclear size. The five-year survival rate for grade 1 tumors is 90%, grade 2 tumors is 81% and grade 3 tumors is 43%. The ten-year survival rates are 83%, 64%, and 29% for grades 1, 2, and 3 tumors, respectively. Local recurrence is highly dependent on surgical margins [13,15,16]. Costal chondrosarcoma is a challenge to treat, as wide resection with resection of multiple ribs can result in flail chest [17].

Conclusion
Primary chondrosarcoma of the chest wall differential diagnosis presenting with an enlarging firm, immobile painless deeply seated breast mass. Mammogram will demonstrate a retropectoral mass with central calcifications. CT and T2-weighted MRI will demonstrate a mineralized septated lesion and a lobular hyperintense mass, respectively.