Bizarre Parosteal Osteochondromatous Proliferation: A Locally Aggressive Benign Tumor

Abstract

Background Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign lesion of bone, and numerous questions remain unresolved regarding its etiology, diagnosis, and treatment. Questions/purposes We present the Scottish Bone Tumour Registry experience of this rare lesion. Patients and MethodsWe performed a retrospective analysis of the Scottish Bone Tumour Registry records. Histologic specimens were reexamined by a musculoskeletal pathologist. Radiographs were reevaluated by a musculoskeletal radiologist.Results From 1983 to 2009, 13 cases (13 patients; six male, seven female) were identified. Their ages ranged from 13 to 65 years. All patients presented with localized swelling. Pain was present in five. Antecedent trauma was present in two. Nine lesions affected the hand, three the foot, and one the tibial tuberosity. Twelve lesions were excised and one was curetted. There were seven recurrences of which six were excised. One lesion recurred a second time and was excised. There were no metastases. Radiographs showed densely mineralized lesions contiguous with an uninvolved cortex. Cortical breakthrough was present in one case and scalloping in another. Histologic analysis characteristically showed hypercellular cartilage with pleomorphism and calcification/ossification without atypia, bone undergoing maturation, and a spindle cell stroma. Conclusions BPOP is a rare benign lesion that probably is neoplastic, with no gender predilection, and affecting patients over a wide age range. Previously trauma was considered an etiologic factor, but this no longer seems to be the case. The rate of recurrence was 50%, which may indicate a more extensive resection is required for this locally aggressive lesion. No metastases were reported.

Asymptomatic Upper Arm Mass in a 37-year-old Woman

“…This maturation process has been hypothesized to represent a reparative etiology in the response to trauma [11,24,27], despite that the majority of patients described in case reports lack a traumatic history. More recently, some reports have suggested BPOP is a neoplastic process instead of a reparative one [7,12,17,22,26,28].…”

“…Diagnosis of BPOP typically is based on a combination of radiographs and histology, although radiographically classic lesions can be diagnosed without histopathologic confirmation [12]. The classic radiographic appearance of BPOP is a well-defined, mineralized round or oval mass with a broad base that arises from the cortex without flaring or corticomedullary continuity [14,18].…”

“…MRI is useful to further characterize the radiographic features and display pertinent negatives, such as the absence of soft tissue swelling, soft tissue mass, and cortical destruction. Several case reports described histologically confirmed BPOP with atypical radiographic features, including cortical invasion, corticomedullary continuity, and medullary inflammation [1,10,12,19,21,22,26]. In these studies, histologic examination of the lesions was necessary to make the diagnosis.…”

“…The bone component of BPOP consists of well-formed trabeculae of woven bone enmeshed in loose connective tissue [1,14,15,23]. Surgery is the standard treatment for BPOP; however, the appropriate margins of resection are debated owing to the high incidence of recurrence [6,12,14,18,23]. Surgical approaches include marginal resection and continued local resection of any recurrent lesions.…”

“…Berber et al [3] reviewed 22 cases of BPOP treated with either marginal or wide resection and found similar recurrence rates of 28.6% and 25% respectively, with a mean followup of 32 months. The recurrence times reported in the literature range from 2 to 84 months [12,18]. Yeun et al [27] suggested recurrence is a result of premature excision and not surgical margins but no data currently support this.…”