"Ring and arc" calcification in a rib mass.

A 42-year-old female presented with complaints of progressively increasing right shoulder pain of 6 months duration along with low-grade fever. She was evaluated at another center, and based on radiology (chest X-ray), she was started on anti-tubercular treatment with which she had no response.

Physical and neurologic examinations were normal. Chest radiography revealed a partially calcified mass in the right upper zone area [Figure 1]. Routine hematological investigations and repeated bacteriological examinations of the sputum were normal.

Figure 1

Chest radiograph showing a right upper lobe mass lesion

A computed tomography (CT) scan of the chest revealed a 4 cm × 5 cm lobulated mass arising from the right second posterior rib [Figure 2]. The mass revealed scattered calcification(ring and arc pattern). There were no other bony lesions or enlarged lymph nodes so as to suggest a metastatic disease. The tumor was excised along with the second rib.

Figure 2

Non-contrast computed tomography of chest revealing a mass lesion with ring and arc calcification

Q1. What is your diagnosis?

ANSWER

Chondrosarcoma of 2nd rib

DISCUSSION

Histopathological examination revealed myxoid chondroid matrix, increased cellularity, and chondrocytes consistent with diagnosis of chondrosarcoma [Figure 3].

Figure 3

Histopathology showing myxoid chondroid matrix and increased cellularity

Chondrosarcoma is a rare malignant tumor of bone that produces cartilage matrix. The estimated annual incidence has been reported as 1 in 200,000.[1]

Chondrosarcomas often arise in the pelvis or bones of the trunk, but primary chest wall chondrosarcomas are relatively rare.[2] Chondrosarcomas are typically located anteriorly within the chest wall, arising from the sternum or costochondral arches,[3] but in this case it originated from the right second rib posteriorly which is an unusual site.

Radiographs of chondrosarcoma typically reveal a mixed lytic and sclerotic appearance. The sclerotic areas represent chondroid matrix mineralization and are seen in 60–78% of lesions. The characteristic appearance of mineralized chondroid matrix is a ring and arc pattern of calcification. This characteristic chondroid calcification usually allows confident radiologic diagnosis of a cartilaginous lesion.[4] The index case had a classic “ring and arc” calcification within a well-circumscribed rib mass, highly suggestive of chondrosarcoma.