Immunophenotyping of an Unusual Mixed-Type Extraskeletal Osteosarcoma in a Dog

A 6-year-old female Maltese dog presented with a cervical mass without pain. The tumor was surrounded by a thick fibrous tissue and consisted of an osteoid matrix with osteoblasts and two distinct areas: a mesenchymal cell-rich lesion with numerous multinucleated giant cells and a chondroid matrix-rich lesion. The tumor cells exhibited heterogeneous protein expression, including a positive expression of vimentin, cytokeratin, RANKL, CRLR, SOX9, and collagen 2, and was diagnosed as extraskeletal osteosarcoma. Despite its malignancy, the dog showed no sign of recurrence or metastasis three months after the resection. Further analysis of the tumor cells revealed a high expression of proliferation- and metastasis-related biomarkers in the absence of angiogenesis-related biomarkers, suggesting that the lack of angiogenesis and the elevated tumor-associated fibrosis resulted in a hypoxic tumor microenvironment and prevented metastasis.

Chondroblastoma of bone: case presentation, immunohistochemistry findings and literature review

Chondroblastoma is a rare benign cartilage-producing tu­mor, with an incidence of approximatively 1% of all pri­ma­ry bone tumors. It arises mostly in the second decade of life, affecting mainly the ends of the long tubular bones. We present two cases of chondroblastoma diagnosed and trea­ted in the “Foişor” Orthopedics, Traumatology and Oes­teo­articular TB Clinical Hospital, Bucharest, Romania. The purpose of this study is to contrast two different forms of presentation of the same histologic entity: one case of a 19-year-old male patient with a chondroblastoma lo­ca­ted in the proximal humerus, and the case of a 37-year-old male patient with a chondroblastoma of the cal­ca­neus. The mor­phological fea­tures, radiologic aspects and im­mu­no­his­tochemical stu­dies have been assessed. None of the cases presented with spe­ci­fic radiologic signs for chondroblastoma, both lesions being osteolytic and well-delineated, in favor of a benign en­ti­ty. The classic mor­pho­lo­gical aspects of chondroblastoma re­pre­sen­ted by tumor cells with round poly­gonal shape and nuclei with longitudinal grooves were as­so­cia­ted with variable amounts of chondroid matrix, pe­ri­cellular calcification and few randomly distributed osteo­clast-like giant cells. The im­mu­no­his­to­chemical studies showed the osteoblastic and chon­dro­blastic phenotype of the neoplastic cells, sustained by positivity for CD56 and S100. DOG1, cytokeratin 8/18 and smooth muscle actin (SMA) were also found focally po­si­tive. All cases were treated by curettage with bone graf­ting, without recurrence in the short-term follow-up. Given the nonspecific radiologic findings and the histologic he­te­ro­ge­nei­ty, chondroblastoma is sometimes misinterpreted as a ma­lig­nant tumor, while this neoplastic lesion has a benign be­havior and benefits from conservative surgical treatment only.

Chondrosarcoma in petroclival synchondrosis without visual change

Chondrosarcomas are a heterogeneous group of malignant bone tumours that share the production of the chondroid matrix in common. At the base of the skull, they are most commonly found in the region of the various synchondroses with an affinity for the petroclival fissure, they are locally invasive tumours, with little capacity to perform metastasis. The age group affected is variable, however, they frequently occur in middle-aged adults. Its clinical manifestation depends on the location and local extent; headache or paralysis of cranial nerves, particularly of the VI nerve is a frequent sign. As the petrous apex cannot be viewed directly, imaging studies such as computed tomography and magnetic resonance imaging play an important role in the evaluation of injuries. We present a case of a 36-year-old patient with chondrosarcoma of petroclival syndromes without visual changes. For the identification of this pathology, a battery of imaging tests was used and the diagnosis was made assertively, preserving the best choices for the treatment of the patient.

Malignant Chondroid Matrix Bone Tumors

Chapter 55 discusses malignant chondroid matrix bone tumors. Chondrosarcoma is a malignant bone tumor of cartilage origin. It represents the third most common primary malignant bone tumor, after multiple myeloma and osteosarcoma. Conventional intramedullary chondrosarcoma is its most common subtype, with rarer subtypes that include clear cell, mesenchymal, dedifferentiated, and periosteal chondrosarcoma. Secondary chondrosarcoma represents a lesion that arises in a preexisting benign chondroid lesion (enchondroma or osteochondroma). Chondrosarcomas demonstrate some specific imaging features that can improve diagnostic accuracy and help guide clinical management. Histological grade of central chondrosarcoma usually dictates surgical management. As with other sarcomas, outcome of chondrosarcoma depends on histological grade, surgical margins, and staging.

Benign Chondroid Matrix Bone Tumors

Chapter 54 discusses benign chondroid matrix bone tumors, which are the most common benign primary bone tumors. They include osteochondroma, enchondroma, periosteal chondroma, chondroblastoma, and chondromyxoid fibroma. Osteochondromas are bony exostoses that are the most common benign bone tumor in all ages. Most of these neoplasms have characteristic imaging features that can allow accurate diagnosis. Radiography is the mainstay modality of choice for initial workup. MRI and CT can provide increased diagnostic confidence and accuracy, and have become essential tools that guide clinical management of the benign cartilage bone tumors. Treatment can be surgical, including bone grafting, or with radiofrequency ablation.

Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig

Odontoameloblastomas (previously incorporated within ameloblastic odontomas) are matrix-producing odontogenic mixed tumors and are closely related in histologic appearance to the 2 other types of matrix-producing odontogenic mixed tumors: odontomas and ameloblastic fibro-odontomas. The presence or absence of intralesional, induced non-neoplastic tissue must be accounted for in the diagnosis. Herein we describe a naturally occurring odontoameloblastoma with extensive chondroid cementum deposition in a guinea pig ( Cavia porcellus). Microscopically, the mass featured palisading neoplastic odontogenic epithelium closely apposed to ribbons and rings of a pink dental matrix (dentinoid), alongside extensive sheets and aggregates of chondroid cementum. The final diagnosis was an odontoameloblastoma given the abundance of odontogenic epithelium in association with dentinoid but a paucity of pulp ectomesenchyme. Chondroid cementum is an expected anatomical feature of cavies, and its presence within the odontoameloblastoma was interpreted as a response of the ectomesenchyme of the dental follicle to the described neoplasm. Our case illustrates the inductive capabilities of odontoameloblastomas while highlighting species-specific anatomy that has resulted in a histologic appearance unique to cavies and provides imaging and histologic data to aid diagnosis of these challenging lesions.

Gross and histological evaluation of early lesions of navicular bone and deep digital flexor tendon in horses

The study aimed at evaluation of pathological lesions on flexor surface of navicular bone and deep digital flexor tendon in horses graded in standard X-ray examination as 2 (fair). The evaluation was performed on fifteen horses (6-9 years of age). Analysis procedure involved examining navicular bones on X-ray pictures, post-slaughter preparation of navicular bones from the hoof capsule, macroscopic evaluation of fibrocartilage on flexor surface, and analysis of histologic preparations. In horses with navicular bones graded as 2, early pathological changes have already developed, even if such horses were not lame. The pathological changes included fibrillation and disruption of deep digital flexor tendon surface, loss of fibrocartillage in sagittal ridge area of navicular bone, thinning of subchondral bone on its flexor surface, and fibromyxoid changes in chondroid matrix. In terms of clinical relevance, more studies are needed to understand the sequence of changes in a better way.

Extraskeletal Chondroma on the Sole of the Foot

A 47-year-old female presented with a solitary mass located in the plantar region of her left foot. The mass, which she noticed 2 years ago, grew gradually and caused increasing pain when bearing weight. Physical examination showed a 3.5-cm diameter tender nonmobile mass with firm consistency in the midplantar region. Radiographs showed a ring-like calcification compatible with cartilage tissue. Magnetic resonance imaging revealed a lobulated mass with a hypointense signal on T1-weighted images and a hyperintense signal on T2-weighted images in the mid-substance of the plantar fascia. After a skin incision was performed, the mass was dissected from the skin and subcutaneous tissue. Then, a marginal excision was performed. The histological assessment reported chondrocytes within lacunae embedded in a chondroid matrix with focal calcification. The definitive diagnosis was extraskeletal chondroma. Plantar pain resolved within 3 months and no recurrence was found at the 1-year follow-up. Level of Evidence: Therapeutic Level IV, Case Report