A large extraskeletal osteochondroma of the foot

Enlarged Reactional Periostitis of the Peroneal Tubercle Mimicking Osteochondromatosis of the Calcaneus: A Case Report

Foot and ankle tumors are relatively rare. Nevertheless, the calcaneus is a prevalent location accommodating various lesions. Reactional periostitis of the lateral wall is rarely encountered but can potentially mimic a wide variety of tumors. We present a case of excessive proliferation due to chronic compression of the peroneal tendons against the calcaneus in a female patient with a history of diminished foot control, treated successfully by tumor excision and peroneal restoration via the tubularization technique. This study aimed to underline the mimicking potential of reactional periostitis and its effect on the peroneal tendons and hindfoot motion.

Extraskeletal Osteochondroma of the Great Toe in a Teenager

Osteochondromas are common, benign surface tumors of bone, composed of the cartilage-capped bone confluent with the medullary canal of the metaphyseal bone. Extraskeletal osteochondromas have the same gross appearance and histologic characteristics as a typical osteochondroma but do not have any boney attachment to the surrounding osseous structures. They are rare and most frequently reported in the middle-age and older adults. We present the first case of an extraskeletal osteochondroma of the foot reported in a teenager. Our patient was a 17-year-old male complaining of a slow-growing mass along the medial border of the great toe that he first noted at the age of 14 years. The increasing size of the mass and frequency of complaints with shoe wear prompted medical attention. Imaging studies showed an ossified 1-cm boney mass with trabecular detail, located on the medial aspect of the great toe at the level of the interphalangeal joint, without any connection to the surrounding structures. An excisional biopsy revealed a well-circumscribed, easily removable mass, which proved to be an extraskeletal osteochondroma both clinically and histologically.

Extraskeletal osteochondroma within the iliopsoas muscle: case report

Osteochondromas, occurring usually in the metaphyses of long bones, are among the most frequent benign musculoskeletal neoplasms and both their sporadic and hereditary variants have been studied extensively. Extraskeletal osteochondromas, however, are much less common. They have been shown to arise near joints or synovial spaces of feet, hands, or bursae. Herein, we present a very rare case of an extraskeletal osteochondroma within the iliopsoas muscle.

NFAT restricts osteochondroma formation from entheseal progenitors

Osteochondromas are common benign osteocartilaginous tumors in children and adolescents characterized by cartilage-capped bony projections on the surface of bones. These tumors often cause pain, deformity, fracture, and musculoskeletal dysfunction, and they occasionally undergo malignant transformation. The pathogenesis of osteochondromas remains poorly understood. Here, we demonstrate that nuclear factor of activated T cells c1 and c2 (NFATc1 and NFATc2) suppress osteochondromagenesis through individual and combinatorial mechanisms. In mice, conditional deletion of NFATc1 in mesenchymal limb progenitors, Scleraxis-expressing (Scx-expressing) tendoligamentous cells, or postnatally in Aggrecan-expressing cells resulted in osteochondroma formation at entheses, the insertion sites of ligaments and tendons onto bone. Combinatorial deletion of NFATc1 and NFATc2 gave rise to larger and more numerous osteochondromas in inverse proportion to gene dosage. A population of entheseal NFATc1- and Aggrecan-expressing cells was identified as the osteochondroma precursor, previously believed to be growth plate derived or perichondrium derived. Mechanistically, we show that NFATc1 restricts the proliferation and chondrogenesis of osteochondroma precursors. In contrast, NFATc2 preferentially inhibits chondrocyte hypertrophy and osteogenesis. Together, our findings identify and characterize a mechanism of osteochondroma formation and suggest that regulating NFAT activity is a new therapeutic approach for skeletal diseases characterized by defective or exaggerated osteochondral growth.

A Huge Capital Drop with Compression of Femoral Vessels Associated with Hip Osteoarthritis

A capital drop is a type of osteophyte at the inferomedial portion of the femoral head commonly observed in hip osteoarthritis (OA), secondary to developmental dysplasia. Capital drop itself is typically asymptomatic; however, symptoms can appear secondary to impinge against the acetabulum or to irritation of the surrounding tissues, such as nerves, vessels, and tendons. We present here a case of unilateral leg edema in a patient with hip OA, caused by a huge bone mass occurring at the inferomedial portion of the femoral head that compressed the femoral vessels. We diagnosed this bone mass as a capital drop secondary to hip OA after confirming that the mass occurred at least after the age of 63 years based on a previous X-ray. We performed early resection and total hip arthroplasty since the patient's hip pain was due to both advanced hip OA and compression of the femoral vessels; moreover, we aimed to prevent venous thrombosis secondary to vascular compression considering the advanced age and the potent risk of thrombosis in the patient. A large capital drop should be considered as a cause of vascular compression in cases of unilateral leg edema in OA patients.

Rearrangement of chromosome bands 12q14~15 causing HMGA2-SOX5 gene fusion and HMGA2 expression in extraskeletal osteochondroma

We describe two cases of extraskeletal osteochon-droma in which chromosome bands 12q14~15 were visibly rearranged through a pericentric inv(12). Molecular analysis of the first tumor showed that both transcript 1 (NM_003483) and transcript 2 (NM_003484) of HMGA2 were expressed. In the second tumor, the inv(12) detected by karyotyping had resulted in an HMGA2-SOX5 fusion transcript in which exons 1–3 of HMGA2 were fused with a sequence from intron 1 of SOX5. The observed pattern is similar to rearrangements of HMGA2 found in several other benign mesenchymal tumors, i.e., disruption of the HMGA2 locus leaves intact exons 1–3 which encode the AT-hook domains and separates them from the 3′-terminal part of the gene. Our data therefore show that a subset of soft tissue osteochondromas shares pathogenetic involvement of HMGA2 with lipomas, leiomyomas and other benign connective tissue neoplasms.