A 36-Year-Old Woman with a Toe Mass (2004)

LEARNING OBJECTIVES On completion of this study, the reader should be able to: compose a differential diagnosis of benign periosteal proliferative lesions; differentiate between infectious, neoplastic, and reactive lesions; select appropriate therapy depending on the underlying nature of the lesion, as well as recognize patient symptoms. HISTORY AND PHYSICAL EXAMINATION An otherwise healthy 36-year-old woman presented with a soft tissue mass of her right second toe. The patient had noted the lesion during the past 2 months and did not recall any preceding trauma. She denied any recent weight loss, fever, or chills. Her medical history was unremarkable. On physical examination, a firm soft tissue mass of the distal second toe was seen. It was not mobile, and there was no associated tenderness, fluctuance, overlying erythema, or warmth. Sensation was normal in the toe and distal foot, and a negative Tinel’s sign of the posterior tibial nerve was elicited. Normal laboratory values included a serum chemistry panel, hemoglobin, leukocyte count, and erythrocyte sedimentation rate. Conventional radiographs (Fig 1) and MRI scans (Figs 2–3) were obtained.Fig 1.: Conventional radiograph of the foot.Fig 2.: Coronal (A) T1- and (B) T2-weighted spin echo images.Fig 3.: Axial T2-weighted images.Based on the history, physical examination, laboratory evaluation, and imaging studies, what is the differential diagnosis? IMAGING STUDIES INTERPRETATION Conventional radiographs of the foot revealed a soft tissue mass attached to the medial midshaft of the proximal phalanx of the right second toe. There was extrinsic scalloping of the adjacent cortex and a prominent periosteal reaction, somewhat ill-defined in its most distal aspect, resembling an overhanging cortical edge (Fig 1). No increased lysis or sclerosis of the intramedullary bone was seen. Magnetic resonance imaging of the right second toe with sequences including T1- and T2-weighted images was done. The coronal T1-weighted spin echo images (Fig 2) showed a mass of intermediate signal intensity adjacent to the proximal phalanx. The decreased T1-signal in the marrow could represent underlying marrow edema or intramedullary extension from the lesion. Axial T1- and T2-weighted images (Fig 3) showed the mass tightly opposed to the medial bone cortex and extending between the flexor tendons and the inferior cortex. This is partially obscured by edema. T2 signal intensity was increased markedly. The medial cortical bone is appreciated best on the axial T1 images and is increased in thickness but extrinsically saucerized. DIFFERENTIAL DIAGNOSIS Parosteal osteosarcoma Periosteal osteosarcoma Osteomyelitis Juxtacortical heterotopic ossification (myositis ossificans) Florid reactive periostitis Subungal exostoses Bizarre parosteal osteochondromatous proliferation A needle biopsy was done (Figs 4–6). Fig 4.: Photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×100).Fig 5.: Higher power photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×200).Fig 6.: Photomicrograph shows bland fibrous tissue and adjacent hypercellular areas. (Stain, hematoxylin and eosin; magnification, ×40).Based on the history, physical examination, imaging studies, and histologic picture, what is the diagnosis and how should this lesion be treated? See page 319 for diagnosis and treatment. Continuation of ORP Conference from page 318. HISTOLOGIC EXAMINATION A needle biopsy was done and microscopic examination revealed fragments of bony, cartilaginous and fibrous tissue, with structural architectural changes and binucleated cells and giant cells. The patient had elective excision of the lesion. The definitive specimen was submitted as multiple fragments of pale tan soft tissue, measuring as much as 1 cm in greatest dimension. Microscopic examination revealed a small fragment of bone and islands of hypercellular cartilage. Adjacent areas of polygonal and giant cells also were appreciated (Fig 4). Sections showed whorled nests of hyaline cartilage with large, sometimes bizarre nuclei (Fig 5). Several binucleated cells were identified. Irregular blending of cartilage into bone was appreciated, with bland fibrous tissue and osteoclastic giant cells and a small quantity of unremarkable skin and soft tissue (Fig 6). DIAGNOSIS Florid reactive periostitis TREATMENT AND DISCUSSION In general, osteochondromatous proliferations are common, and most tend to be found in the long bones.2 Some, however, have a propensity for the small tubular bones of the hands and feet.2 Among these are florid reactive periostitis, bizarre parosteal osteochondromatous proliferation, and subungal exostosis.2 Florid reactive periostitis is a reactive lesion described 2 decades ago, and previously called parosteal fasciitis or nodular fasciitis.6,8 A variably aggressive periosteal reaction on radiographs is typical,2,8 and soft tissue swelling is prominent.2,8,9 Although several authors propose a traumatic etiology,6,9 an antecedent history of trauma is not always elicited.6 This condition has a predisposition for the hands and feet, arises from the periosteum, and contains osteoid with a fibroblastic stroma and cartilaginous components.5 Because the clinical symptoms may simulate those of infection or neoplasm, florid reactive periostitis and other osseochondromatous lesions may be mistaken for a more aggressive lesion.8 Moreover, the often atypical histologic appearance of the lesion sometimes leads to a misdiagnosis of malignancy.6,8 Factors suggestive of a diagnosis of florid reactive periostitis rather than neoplasm include soft tissue swelling of a greater extent than expected for the degree of periosteal reaction, and lack of bony disruption.8 Florid reactive periostitis lesions often present as a firm, well-defined mass or swelling, most frequently in the hands or feet, although cases have been described in the long bones.1,6,8 Pain or tenderness may or may not be present.4,6 Although florid reactive periostitis may present in patients at any age, adolescents and young adults are affected most commonly.1 Frequently, the patent is referred to the orthopaedist or hand surgeon with a swollen digit and radiographs showing soft tissue swelling and a periosteal reaction, suspicious for osteomyelitis or more rarely, suggestive of malignancy.6 Plain radiographs typically show features consistent with a benign process, with swelling and sometimes calcification of the soft tissues.1 A periosteal reaction usually is present, most commonly in the setting of an intact cortex.1 Although the cortex rarely is disturbed, several cases in which cortical destruction was observed on radiographic examination were reported.1 In such settings, the destructive appearance of the lesion and the clinical history of rapid growth again may raise the suspicion of malignancy.1 Although conventional radiographs usually appear benign, MRI scans may be more worrisome.1 Magnetic resonance imaging scans show soft tissue swelling and other changes suggestive of infectious or neoplastic processes.1 T1-weighted images show low to intermediate intensity9 of the soft tissue mass, whereas T2-weighted reveal heterogeneous increased intensity.2,9 The imaging presentation of the current case was atypical with the adjacent marrow signal abnormalities and lack of visible calcification within the mass. Although the adjacent cortex was thickened, it appeared extrinsically saucerized. This cortical involvement is uncommon but has been reported previously.6 Grossly, the lesion is characterized as a fibrous to bony, gritty, gray-white mass.1,6 Histologic features include a heterogeneous collection of osteoid, bone, cartilage, and fibrous tissue.6 Areas of hypercellular cartilage with large nuclei may be present in islands.1,6 Abundant osteoid, suggestive of a neoplastic process, and a myxoid or chondromyxoid stroma may be present with scattered multinucleated giant cells and rare inflammatory cells.1,6 Large, pleomorphic spindled cells with hyperchromatic nuclei and frequent, albeit typical mitoses, the abundant osteoid, and the often infiltrative pattern of the lesion may mimic osteosarcoma.1,6 The differential diagnosis encompasses benign and malignant processes,7 including osteochondroma, other reactive changes, parosteal osteosarcoma, and others.5 It is, however, important to make the correct diagnosis, because these lesions frequently have a different prognosis and treatment than mimickers.5 Likewise, osteomyelitis and soft tissue infections must be excluded.8 Other conditions to consider in the workup of an osseochondromatous lesion include bizarre periosteal osteochondromatous proliferation3 and turret or subungal exostosis.5 Osteochondromas are cartilage-capped, fibroosseous proliferations of cortical bone locale.5,9 However, in contrast to bizarre parosteal osteochondromatous proliferation or florid reactive periostitis, osteochondromas rarely occur in the small bones of the hands and feet, and commonly shows involvement of underlying bony tissue,9 continuity with the marrow and cortical flaring.2,8 Myositis ossificans, an ossifying process of soft tissues of unknown etiology,5 may be identified by its central area of immature tissue, with progressive maturation toward the periphery.5 Other causes of abnormal calcification of soft tissue, particularly in children, should be considered; among them, dermatomyositis and various endocrinopathies.5 Progressive ossesous heteroplasia recapitulates encondromal bone formation in ectopic sites, with progressive calcification and ossification in the soft tissues of afflicted children.5 Another consideration in the differential diagnosis of an osseochondromatous lesion is stress fracture with callus formation.1,9 In the early phases of fracture callus formation, histologic features may be suggestive of florid reactive periostitis or of osteosarcoma, especially if a biopsy specimen is obtained in the first 2 to 4 weeks after injury.1 A subsequent biopsy specimen obtained 2 to more months after injury will reveal the mature lamellar bone with osteoblastic rimming typical of fracture callus.1 A history of recurrent trauma is typical in the setting of stress fractures, and MRI scans can show cortical and medullary involvement by fracture.1,9 Bizarre parosteal osteochondromatous proliferation, similar to florid reactive periostitis, is a reactive lesion affecting primarily tubular bones of the hands and feet,3,8 and is thought to be secondary to trauma; however, an antecedent history of trauma is not always elicited.8 Clinical features to differentiate bizarre parosteal osteochondromatous proliferation and florid reactive periostitis include the propensity of the former to recur after excision3,7 sometimes in different locations or multiple times.8 Likewise, radiographic and pathologic findings may help differentiate between the two lesions.1 Radiologic characteristics of bizarre parosteal osteochondromatous proliferation include more prominent calcification of the lesion1 and a lack of soft tissue swelling, in contrast to florid reactive periostitis.9 Although florid reactive periostitis and bizarre parosteal osteochondromatous proliferation may share some overlapping histologic features, abnormal mitoses are common in bizarre parosteal osteochondromatous proliferation, but rarely are seen in florid reactive periostitis.1,5,8 Similarly, bizarre parosteal osteochondromatous proliferation commonly has a typical, albeit not pathognomonic, blue tinctural appearance on hematoxylin and eosin stains.2,4,5,8 Turret exostosis, similar to florid periostitis, is a reactive lesion originating from the periosteum, with a bony component encased by cartilage.5,7 This lesion is seen most commonly in the proximal or midphalanges.7,9 Clinical presentation is as a broad-based ossified protuberance in continuity with the subjacent bone and encapsulated by cartilage peripherally7,9 and symptoms may include a painful enlarging mass and/or limited ROM.7 Subungal exostosis is differentiated by anatomic site, because it afflicts the distal phalanges2,8 and is found more commonly in the foot.2 Several authors have hypothesized that florid reactive periostitis, bizarre parosteal osteochondromatous proliferation, and turret exostosis exist as a spectrum of the same pathophysiologic process with differing anatomic factors and different levels of maturation and organization, because they have overlapping clinical, histologic, and radiologic features.2,7,8,10 Sundaram et al8 investigated a series of three patients with lesions initially diagnosed as florid reactive periostitis. Close clinical and radiographic followup was maintained until biopsy (2–8 months) then for the following 9 to 13 months.8 Histologically, the biopsy specimens revealed florid reactive periostitis, but in one case, radiographic followup showed apparent progression to bizarre parosteal osteochondromatous proliferation.8 A second lesion likewise seemed to progress to bizarre parosteal osteochondromatous proliferation radiographically, although not confirmed by biopsy.8 This series suggests that it may be prudent in cases of florid reactive periostitis to delay surgery and closely monitor the lesion, because it may mature and ossify, making excision more easy.7,8 Likewise, Sundaram et al8 proposed that florid reactive periostitis may be self-limiting or may mature to bizarre parosteal osteochondromatous proliferation;8 the hypothesis being that subperiosteal hemorrhage matures into a bony and cartilaginous proliferation (florid reactive periostitis), and subsequently develops periosteal bone formation and metaplastic cartilaginous growth (bizarre parosteal osteochondromatous proliferation).7,10 As the lesion further develops into turret exostosis, a bony base in apposition to the underlying cortex is seen with peripheral cartilage encasement.7 If a decision is made to obtain a biopsy specimen, representative specimens should be obtained from the center and edges of the lesion, and intraoperative frozen sections may be helpful to gauge adequacy of sampling.1 Because the clinical, pathologic, and sometimes radiographic presentations of this lesion have overlapping features with more serious conditions, including infection and malignancy, the treatment of choice for florid reactive periostitis seems to be local excision.1,7 Nevertheless, in selected situations, conservative measures including observation and ROM exercises also have been shown to result in good outcomes.1 Although florid reactive periostitis is rare and the clinical and pathologic experience spans only 2 decades, statistically, a lesion of the small bones of the distal extremities is more likely to be florid reactive periostitis or another benign osseochondromatous proliferation than a malignancy.8 Therefore, diagnosis of a reactive process should be considered with a soft tissue mass in the setting of an intact bone and prominent periosteal reaction.8 Differentiation from infectious complications, however, is essential.8 Subsequent radiographs in 7 to 10 days and with consideration of the clinical presentation usually are adequate to rule out bony or soft tissue infection.8 In the current case, because the lesion seemed to be attached to the adjacent bone radiologically and this was confirmed during surgery, the cortex was not opened during the resection. Therefore, we cannot state with certainty whether the medullary cavity of the phalanx was involved. However, 9 months postoperatively there is no evidence of recurrence. The patient has full function, no limitations, and no pain. Florid reactive periostitis has characteristic histologic and radiographic features; however, these findings overlap with a broad differential, including benign and malignant entities.7,9 Florid reactive periostitis is a benign lesion, with local excision as the treatment of choice.1 In light of the atypical histologic appearance and the rareness of this lesion, careful clinical, radiographic, and pathologic correlation is necessary to avoid misdiagnosis and subsequent errors in treatment modality.1,2,7