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Year : 2008  |  Volume : 51  |  Issue : 1  |  Page : 58-60
Osteochondroma-like parosteal osteosarcoma

Department of Pathology, Narayana Medical College, Nellore, Andhra Pradesh, India

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Parosteal osteosarcoma is a well-differentiated, predominantly fibro-osseous variant of osteosarcoma, accounting for 5% of all osteosarcomas. We report a case of parosteal osteosarcoma in the metaphyseal area of right femur, of 2 years' duration in a male aged 35 years. It was mistaken for osteochondroma in the initial biopsy, and the possibility of bizarre parosteal osteochondromatous proliferation (BPOP) was also considered. Subsequent excision of the tumor showed it to be a parosteal osteosarcoma. The patient had recurrence of the lesion after 1 year, and he attended a cancer institute. Follow-up showed metastases of the tumor on bone scan.

Keywords: Parosteal osteosarcoma, osteosarcoma, osteochondroma

How to cite this article:
Krishna Swaroop DS, Bai SJ, Shanthi V, Ramakrishna B A. Osteochondroma-like parosteal osteosarcoma. Indian J Pathol Microbiol 2008;51:58-60

How to cite this URL:
Krishna Swaroop DS, Bai SJ, Shanthi V, Ramakrishna B A. Osteochondroma-like parosteal osteosarcoma. Indian J Pathol Microbiol [serial online] 2008 [cited 2021 May 13];51:58-60. Available from: https://www.ijpmonline.org/text.asp?2008/51/1/58/40399

   Introduction Top

Parosteal osteosarcoma is a slow-growing malignant tumor arising from periosseous tissues adjacent to the cortex and frequently displays a high degree of histological differentiation. It has a better prognosis than the other varieties of osteosarcoma, from which it has to be differentiated. [1] Sometimes, its aggressiveness has been underestimated, and inadequate treatment has led to repeat local recurrence and occasionally to the development of metastatic disease. [2]

   Case History Top

A 35-year-old male presented with a slow-growing tumor at the lower end of right thigh of 2 years' duration, not associated with pain. Clinically, the tumor was 15 x 10 cm, oval, situated on the antero-lateral aspect of femur and was bony hard. X-ray showed an exophytic, heavily calcified mass at the metaphyseal area, not associated with endosteal spread and a well-demarcated zone of transition [Figure - 1]. CT scan showed dense exophytic mass with a line of demarcation evident between the tumor and the lower end of femur except at the metaphyseal area of base attachment with loss of entire cortical outline. During the surgery, the tumor was seen to be covered by a 'cartilaginous cap'.

Biopsy of the lesion was sent for histopathological examination and it was excised later. After 1 year, the patient presented with recurrence. He was referred to a cancer institute, where metastases in the 5 th rib and iliac bone were identified by a bone scan. The patient was put on palliative treatment.

Pathological findings

Gross : The initial biopsy received consisted of multiple bony fragments, the largest measuring 1 x 0.5 cm, with foci of cartilage.

Microscopic : It showed normal cortical lamellar bone with a "cartilaginous cap" covered by a thin fibrous layer. The lesion was diagnosed as "osteochondroma" in view of the "cartilaginous cap" consisting of normal appearing chondrocytes and fatty marrow in-between the bony trabeculae. However, review of the deeper sections showed small foci of fibroblastic stroma in addition [Figure - 2].

Excised tumor - Gross : Consisted of multiple fragments of bone measuring 6 x 4 x 2 cm.

Microscopic : Examination showed features of parosteal osteosarcoma with long, narrow trabeculae of woven bone, separated by a fibrous stroma [Figure - 3]. The spindled, fibroblastic cells showed minimal cytologic atypia. Few foci of ill-defined osteoid, occasional trabeculae with osteoblastic rimming and cartilaginous islands, were also seen at the periphery. Periosteal osteosarcoma was excluded by the absence of a predominantly chondromatous areas and the lack of prominent radio lucent areas on radiological examination.

Bizarre parosteal osteochondromatous proliferation (BPOP) was excluded as hypercellular cartilage was not seen in the sections.

   Discussion Top

Parosteal osteosarcoma is an uncommon tumor, and even large institutions have limited experience of its management. It occurs less frequently than classic osteosarcoma but nearly twice as common as the periosteal variety of osteosarcoma. [2]

There is no sex preference, although some studies have shown a slight female predilection, [2] and the patients age ranged from childhood to 6 th or 7 th decade of life with a peak in the 2 nd decade. [3]

A majority of the lesions of parosteal osteosarcoma were observed on the posterior aspect of the distal femoral metaphysis, followed by the upper shaft of tibia, humerus, radius, ulna, fibula and rarely the skull, tubular bones of hands and feet. [2],[3]

The duration of symptoms ranged from 1 month to 15 years, and 34% patients as reported by Campanacci et al. [2] had symptoms for more than 2 years, as in our case.

There may be a history of "recurrent osteochondroma" in these patients, the lesion having been repeatedly misdiagnosed. [3] The misdiagnosis in our case could be due to the absence of prominent osseofibrous stroma in the initial superficial biopsy. Lin et al. [4] reported six such cases, which were initially misdiagnosed as osteochondroma.

Osteochondromas are radiographically and microscopically distinct from parosteal osteosarcoma.

In osteochondroma, the underlying cortex and medullary bone are "drawn into" the lesion, rather than having the appearance of a mass "stuck on" the normal cortex as is seen in parosteal osteosarcoma. In osteochondroma, the maximal lesional sclerosis tends to be located peripherally, with the central portions composed of more lucent normal marrow. In contrast, parosteal osteosarcoma are more sclerotic centrally at the site of attachment of the tumor and remains separated from the cortex by a narrow lucent zone producing characteristic radiographic "string sign". [3]

Microscopically, osteochondromas invariably have normal appearing hemopoietic or fibrofatty marrow and lack the fibroblastic stroma, which is the hallmark of parosteal osteosarcoma. The islands of cartilage and cartilage "caps" frequently present at the periphery of parosteal osteosarcoma are microscopically low grade, resembling an enchondroma or low-grade chondrosarcoma and differ from the cartilaginous cap of osteochondroma, which show orderly rows of cartilage cell nuclei. [3]

Bizarre parosteal osteochondromatous proliferation, prior to its description by Nora et al. , [5] were included as "early Juxta cortical osteosarcoma". [6] Although the original reports described these lesions in hands and feet exclusively, subsequently additional sites in long bones, skull and maxilla have been included. [7] These can recur, but metastases detected as in our case unequivocally rules out the possibility of BPOP.

Radiological examination is useful in excluding periosteal osteosarcoma in which radio lucent areas predominate unlike the more sclerotic parosteal osteosarcoma, with a typical mass "stuck on" the cortex. [3]

The fibrous component of both primary and recurrent lesions could be graded from 1 to 4. [2],[8] The fibrous tissue in this case was similar to that in a grade-1 fibrosarcoma with only slight increase in cellularity, little nuclear pleomorphism or hyperchromacity and rare mitoses.

The development of metastases appears to be influenced by increasing histological grade, the invasion or involvement of the medullary cavity by higher grade lesions and the duration of persistent disease in histological grade-II and grade-III tumors. [2] Occurrence of myocardial metastases 13 years after resection has been reported. [9]

In parosteal osteosarcoma, the long-term survival rate is 85.8%. [10] Although it is a well-differentiated tumor, dedifferentiation into a high-grade sarcoma like liposarcoma has been observed. [11] Dedifferentiation has been reported in 16% of patients, and was associated with poor prognosis. [12] Such dedifferentiation markedly increases the risk of metastasis.

Recurrences of inappropriately treated lesions carry an increased risk of medullary involvement with associated poorer prognosis. [3]

Small lesions should be treated with en bloc resection with a margin of uninvolved bone, and larger lesions may require more complex, wide resection with grafts or amputation. [2],[3],[13]

   Conclusion Top

Precise radiological, pathologic evaluation and correlation are essential for appropriate diagnosis and management of this remarkably curable tumor.

   References Top

1.Dahlin DC, Unni KK. Osteosarcoma of bone and its important recognizable varieties. Am J Surg Pathol 1977;1:61-72.  Back to cited text no. 1  [PUBMED]  
2.Campanacci M, Picci P, Gherlinzoni F, et al . Parosteal osteosarcoma. J Bone Joint Surg Br 1984;66-B:313-21.  Back to cited text no. 2    
3.Fechner RE, Mills SE. In : Rosai J, Leslie H, editors. Atlas of tumor pathology. Third series, Fascicle 8. Armed forces Institute of Pathology: Washington; 1992. p. 65-70.  Back to cited text no. 3    
4.Lin J, Yao L, Mirra JM, et al . Osteochondroma like parosteal osteosarcoma: A report of 6 cases of a new entity. AJR Am J Roentgenol 1999;172:1447.  Back to cited text no. 4    
5.Nora FE, Dahlin DC, Beabout JW. Bizarre parosteal osteochondromatous proliferations of the hands and feet. Am J Surg Pathol 1983;7:245-50.  Back to cited text no. 5  [PUBMED]  
6.Jacobson SA. Early juxtacortical osteosarcoma (parosteal osteosarcoma). J Bone Joint Surg Am 1958;40:1318-28.  Back to cited text no. 6    
7.Meneses MF, Unni KK, Swee RG. Bizarre parosteal osteochondromatous proliferation of bone (Noras lesion). J Bone Joint Surg Am 1994;76:366-78.  Back to cited text no. 7    
8.Campanacci M, Olmi R. Fibrosarcoma of bone: A study of 114 case. Ital J Orthop Traumatol 1977;3:201-8.  Back to cited text no. 8    
9.Santos-Machado TM, Oliveira CR, Croci AT, et al . Parosteal osteosarcoma with myocardial metastasis 13 years after follow up. Rev Hosp Clin Fac Med Sao Paulo 2003;58:113-8.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]
10.Ding Y, Cai YB, Zhang Q. Parosteal osteosarcoma: A clinical study of 48 cases. Zhonghua Wai Ke Za Zhi 2003;41:832-6.  Back to cited text no. 10  [PUBMED]  
11.Parmar DN, Luthert PJ, Cree IA, et al . Two unusual osteogenic orbital tumors: Presumed parosteal osteosarcoma of the orbit. Ophthalmology 2001;108:1452-6.  Back to cited text no. 11  [PUBMED]  [FULLTEXT]
12.Okada K, Frassica FJ, Sim FH, et al . Parosteal osteosarcoma. A clinicopathological study. J Bone Joint Surg Am 1994;76:366-78.  Back to cited text no. 12    
13.Hoshi M, Matsumoto S, Manabe J, et al . Oncologic outcome of parosteal osteosarcoma. Int J Clin Oncol 2006;11:120-6.  Back to cited text no. 13  [PUBMED]  [FULLTEXT]

Correspondence Address:
Duddi Sreehari Krishna Swaroop
Department of Pathology, Narayana Medical College, Chinthareddypalem, Nellore - 524 002, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.40399

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  [Figure - 1], [Figure - 2], [Figure - 3]

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