Dedifferentiated adamantinoma with revertant mesenchymal phenotype

Recurrent Adamantinoma With Fibrous Dysplasia-like Feature

Adamantinoma (AD) is a rare, slow-growing primary malignant bone tumor characterized by a biphasic morphology of clusters of epithelial cells and spindle cell osteofibrous components. A strong relationship between AD and osteofibrous dysplasia (OFD) has been proposed, while fibrous dysplasia (FD) has been rarely associated with AD. We present an AD case that was followed and histologically evaluated 3 times over 6 years with different morphological patterns. The tumor in the primary biopsy and after complete resection showed classical features of AD and osteofibrous-like pattern, while the recurrent lesion presented with exclusively spindle cell morphology and was thus diagnosed as FD. However, the extensive immunohistochemical analysis in all 3 lesions revealed strong reactivity for pancytokeratin, vimentin, p63, and podoplanin, which are characteristic for AD. Although, in the FD-like section of the tumor from the first recurrence the positivity of podoplanin was stronger than pancitokeratin, which was variably positive on spindle cells. The present case highlights the problem of diagnosing AD based on a single biopsy with one tumor's component predominating over the other, and at the same time emphasizes the importance of using immunohistochemical staining for keratin and podoplanin when the histopathological features of (osteo)fibrous lesion can be linked to AD.

Update of pediatric bone tumors-other mesenchymal tumors of bone, hematopoietic neoplasms of bone, and WHO classification of undifferentiated small round cell sarcomas of bone

There are numerous bone tumors in the pediatric population, with imaging playing an essential role in diagnosis and management. Our understanding of certain bone tumors has rapidly evolved over the past decade with advancements in next-generation genetic sequencing techniques. This increased level of understanding has altered the nomenclature, management approach, and prognosis of certain lesions. We provide a detailed update of bone tumors that occur in the pediatric population with emphasis on the recently released nomenclature provided in the 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumours. We discuss other mesenchymal tumors of bone, hematopoietic neoplasms of bone, and WHO classification of undifferentiated small round cell sarcomas of bone. We have detailed osteogenic tumors and osteoclastic giant cell-rich tumors, as well as notochordal tumors, chondrogenic tumors, and vascular tumors of the bone in separate manuscripts.

Adamantinoma with a Prominent Spindle Cell Component Mimicking Intraosseous Synovial Sarcoma: Clinicopathological Features of Six Tumors

Introduction. Adamantinoma is sub-classified into classic/biphasic, osteofibrous dysplasia-like, and de-differentiated type. We present six adamantinomas with a prominent spindle cell component mimicking intraosseous synovial sarcomas. Methods. Six patients were either referred with a diagnosis of intraosseous synovial sarcoma or wherein synovial sarcoma was a differential diagnosis. Three tumors were tested for SS18 gene rearrangement by FISH and two for SS18::SSX fusion by RT-PCR technique. Results. There were three males and three females with an average age of 20.6 years. Radiologically, the lesions were expansile and showed lytic and/or sclerotic components, involving the cortex and/or medulla. Five lesions occurred in the tibia and two in the fibula. Two tumors displayed soft tissue extension and two occurred as multifocal lesions. Two patients were diagnosed with synovial sarcoma and a single patient with sarcomatoid carcinoma, elsewhere. Two "in-house" patients were initially diagnosed with synovial sarcomas. On review, all tumors were cellular comprising monomorphic spindle-shaped cells arranged in sheets and fascicles (n = 6), including a "herringbone-like" pattern (n = 3), focal tubules (n = 1), cohesive nests (n = 5), cords (n = 2), including pseudocystic component (n = 2). Immunohistochemically, tumor cells were positive for p63 (6/6), p40 (4/4), EMA (2/3), AE1/AE3 (5/6), various keratins (2/2), and TLE1 (2/4). Three tumors tested for SS18 rearrangement were negative, while two tumors tested for SS18::SSX fusion were negative. Conclusions. Adamantinomas with spindle cell morphology display overlapping features with synovial sarcoma. A clinico-radiological index of suspicion immunostains (p63 and p40) and molecular test for t(X; 18) translocation are useful in an exact diagnosis, which has treatment-related implications.

Osteofibrous Dysplasia and Adamantinoma

For decades, the diagnosis, treatment, and even pathogenesis of the osteofibrous dysplasia/osteofibrous dysplasia-like adamantinoma/classic adamantinoma spectrum of neoplasms have been controversial. Herein, we discuss and illustrate the radiographic and histologic spectrum, differential diagnoses, unifying chromosomal and molecular abnormalities, and current controversies and treatment recommendations for each entity.

Osteosarcoma arising in a case of osteofibrous dysplasia of tibia with classic adamantinoma: A case report and literature review

A five-year-old boy presented with left tibial swelling; there was a typical radiological feature of osteofibrous dysplasia. He was observed until the age of 14 years; there was development of aggressive radiological features. Biopsy revealed chondroblastic osteosarcoma. It was excised and the histology revealed chondroblastic osteosarcoma. A small lesion distal to the main tumour revealed adamantinoma within a background of feature of osteofibrous dysplasia. Proximally, feature of osteofibrous dysplasia was identified focally. The finding of adamantinoma over the distal part of the lesion supports that feature of osteofibrous dysplasia may be a precursor of adamantinoma. They may be a spectrum of diseases with multistep neoplastic transformation. The osteosarcoma may be a result of de-differentiation from adamantinoma. This case is remarkable as the patient was only 14 years old and the tumour showed typical features of osteosarcoma, with feature of osteofibrous dysplasia and adamantinoma found in the same specimen. Feature of osteofibrous dysplasia may be a precursor of adamantinoma, and adamantinoma may dedifferentiate into osteosarcoma.

The 2020 WHO Classification of Tumors of Bone: An Updated Review

Bone tumors are a rare and heterogeneous group of neoplasms that occur in the bone. The diversity and considerable morphologic overlap of bone tumors with other mesenchymal and nonmesenchymal bone lesions can complicate diagnosis. Accurate histologic diagnosis is crucial for appropriate management and prognostication. Since the publication of the fourth edition of the World Health Organization (WHO) classification of tumors of soft tissue and bone in 2013, significant advances have been made in our understanding of bone tumor molecular biology, classification, prognostication, and treatment. Detection of tumor-specific molecular alterations can facilitate the accurate diagnosis of histologically challenging cases. The fifth edition of the 2020 WHO classification of tumors of soft tissue and bone tumors provides an updated classification scheme and essential diagnostic criteria for bone tumors. Herein, we summarize these updates, focusing on major changes in each category of bone tumor, the newly described tumor entities and subtypes of existing tumor types, and newly described molecular and genetic data.

High-grade squamous cell carcinoma arising in a tibial adamantinoma

Adamantinoma of the long bones is a rare, typically low-grade malignant tumor that frequently involves the tibia. Radiographically, adamantinoma is characteristically a lytic, intracortical, and expansile lesion with variable margins. Histologically, adamantinoma is a bimorphic neoplasm, composed of epithelial and osteofibrous elements. Herein, we describe a 72-year-old man with a long-standing tibial mass that, on imaging, rapidly developed cortical destruction with soft tissue extension. Imaging revealed no evidence of a distant site of origin. Needle core biopsy demonstrated high-grade squamous cell carcinoma, and metastasis was initially favored. However, the combined clinicoradiologic and pathologic features were most compatible with a high-grade squamous cell carcinoma arising in adamantinoma. The diagnosis was confirmed in the resection specimen. Both the age at presentation and histologic features make this case unusual and highlight a potential for misdiagnosis in the evaluation of squamous cell carcinoma-containing lesions of the tibia, reinforcing the importance of clinicoradiologic correlation in bone pathology.

Clinicopathologic Features of Two Rare Cases of Dedifferentiated Adamantinomas, Including Diagnostic Implications

A dedifferentiated adamantinoma is a rare subtype of an adamantinoma, associated with a relatively aggressive clinical course, with less than 10 such cases reported so far. A 25-year-old-male presented with pain in his right leg of 1-year duration. Imaging disclosed a well-defined lytic, destructive lesion in his proximal tibia with a cortical break and a soft tissue component. Microscopic examination of the biopsy and resected specimen showed nests and clusters of atypical epithelial cells, along with significant areas showing markedly pleomorphic and spindly sarcomatous cells with interspersed mitotic figures and areas of stromal hyalinization. By immunohistochemistry, the areas of epithelial differentiation showed intense positivity for cytokeratin and p63, whereas the sarcomatous areas showed reduced to absent immunostaining. A 51-year-old lady presented with a recurrent tumor in her right tibia, which was initially diagnosed as an adamantinoma, along with metastatic lesions in her lung. Microscopic examination of the recurrent and metastatic tumors showed areas of epithelial differentiation along with spindly sarcomatous cells, arranged in fascicles. By immunohistochemistry, the areas of epithelial differentiation showed positivity for pan cytokeratin. Additionally, p63 was diffusely positive. p53 showed diffuse and intense staining pattern in the sarcomatous component (dedifferentiation). While the first case is disease-free, the second case is on follow-up. The 2 cases of dedifferentiated adamantinoma further confirm the rare occurrence of this tumor in our population. Its correct diagnosis has treatment implications. Differential diagnoses and literature review of similar reported cases are also presented in this article.

Dedifferentiated giant-cell tumor of bone with an undifferentiated round cell mesenchymal component

The dedifferentiated giant-cell tumor of the bone is a very rare variant of the giant-cell tumor (GCT). We report the clinical, radiographic and histological findings of a dedifferentiated GCT in which the dedifferentiated component consisted of small round cells. We also comment on previously reported cases of dedifferentiated GCT, discuss the clinical implications of this dual histology, and analyze the information published about the coexistence of similar genetic abnormalities in GCT and small round cell tumors of the bone.

Dedifferentiated adamantinoma associated with fibrous dysplasia

A 21-year-old patient presented with an aggressive lesion of the left tibia associated to lymph nodes and lung metastasis. Histological examination revealed a high grade spindle cell sarcoma involving some areas of cytokeratine positive cells. Ultrastructural examination showed the presence of epithelial features in the sarcomatoid cells. The diagnosis of dedifferentiated spindle-celled adamantinoma was established. A second lesion of the right tibia was diagnosed as fibrous dysplasia. The patient had a leg amputation. He died 2 years later with multiple lung and bone metastases. The diagnosis of dedifferentiated adamantinoma should be considered when a clinician is confronted with a tibial biopsy of a "keratin-positive sarcoma". The association with fibrous dysplasia in this case is discussed.

Dedifferentiated classic adamantinoma of the tibia: a report of a case with eventual complete revertant mesenchymal phenotype

Adamantinomas of the long bones are low-grade malignant tumours. They seem to be related to osteofibrous dysplasia with a mesenchymal-to-epithelial transformation. We report a case of an adamantinoma with a revertant sarcomatoid transformation that showed a complete loss of epithelial differentiation. It corresponded to a 41-year-old male presented with an 8-cm multilobated lesion in the centre of the distal tibia. On the en bloc resection specimen, areas of classic adamantinoma were found but most of the tumor corresponded to a high-grade neoplasm with 2 histologic patterns: one made up by epithelial nests with a basaloid arrangement and positive for pankeratins and so-called glandular keratins, and a second sarcomatoid component, negative for these epithelial markers. Five months after surgery the patient had a massive relapse that consisted solely of the second sarcomatous component also negative for epithelial antibodies.Three cases of adamantinomas with sarcomatoid transformation of the epithelial component have been described but the tumours still preserved an epithelial immunophenotype. However, our case represents the extreme end of the sarcomatoid dedifferentiation of a classic adamantinoma with complete sarcomatoid transformation and total loss of epithelial markers. To our knowledge this has not been described previously.

Below-knee amputation through a joint-sparing proximal tibial replacement for recurrent tumour

We report a case which highlights the progression of osteofibrous dysplasia to adamantinoma and questions whether intralesional curettage is the appropriate treatment. The role of a joint-sparing massive endoprosthesis using cortical fixation is demonstrated and we describe a unique biomedical design which resulted in the manufacture of an end cap to allow amputation through a custom-made proximal tibial replacement, rather than an above-knee amputation following recurrence.

Adamantinoma: a clinicopathological review and update

Adamantinoma is a primary low-grade, malignant bone tumor that is predominantly located in the mid-portion of the tibia. The etiology of the tumor is still a matter of debate. The initial symptoms of adamantinoma are often indolent and nonspecific and depend on location and extent of the disease. Histologically, classic adamantinoma is a biphasic tumor characterized by epithelial and osteofibrous components that may be intermingled with each other in various proportions and differentiating patterns. To assure the histological diagnosis, pathologists should employ immunohistochemistry for demonstrating the sometimes sparse epithelial cell nests when the radiological features are suggestive of adamantinoma. There is paucity of compiled data over adamantinoma in the literature, hence authors tried to make a comprehensive review which must be of use to beginners and trained pathologists. Our objective is to further define the clinicoradiologic features and pathologic spectra of adamantinoma.

Apocrine mixed tumor of the skin (“mixed tumor of the folliculosebaceous-apocrine complex”)

BACKGROUND

A systematic analysis of the entire spectrum of various forms of differentiation and metaplastic epiphenomena in cutaneous apocrine mixed tumor (AMT) has never been performed.

OBJECTIVE

The purpose of our study was to study a large number of cutaneous mixed tumors so as to fully characterize the entire spectrum of differentiations and metaplastic changes that may occur in the epithelial, myoepithelial, and stromal components of AMT.

METHODS

This article reports a light-microscopic study of 244 cases of cutaneous AMT, complemented by a literature review.

RESULTS

All types of differentiation along the lines of the folliculosebaceous-apocrine unit can be seen in AMT. The spectrum of metaplastic changes in the epithelial components includes squamous metaplasia, mucinous metaplasia, oxyphilic metaplasia, clear cell change, columnar metaplasia, hobnail metaplasia, and cytoplasmic vacuolization. The following changes in the myoepithelial component were documented: clear cell change, hyaline cells, plasmacytoid cells, spindling, and collagenous spherulosis. Stromal alterations included chondroid metaplasia, osseous metaplasia, and adipose metaplasia.

LIMITATIONS

This study utilizes tissue specimens that mainly came as consultations; therefore some inherent selection bias exists.

CONCLUSIONS

AMT displays a wide range of differentiation and metaplastic changes in its epithelial, myoepithelial, and stromal components. These phenomena are not mutually exclusive. When unduly prominent, they may present diagnostic pitfalls. Our findings corroborate those of previous publications, stressing the remarkable diversity of differentiation and metaplasias that may be found in cutaneous AMT. We propose that the most appropriate name for these lesions is "mixed tumor of the folliculosebaceous-apocrine complex."

Adamantinoma-like Ewing's sarcoma with EWS-FLI1 fusion gene: a case report

Recent studies have advocated the genotypic and phenotypic delineation of a novel Ewing's sarcoma histologic variant showing epithelial features defined as "adamantinoma-like Ewing's sarcoma". We described an 18-year-old girl with a primary small round-cell sarcoma of the right tibia showing polyphenotypic differentiation with epithelioid features. The neoplastic cells had mainly round or oval nuclei with fine chromatin with a portion of epithelial arrangements. The immunohistochemical analysis showed the epithelial markers of cytokeratin 5/6/18, AE1/AE3, and cytokeratin high molecular weight were stained especially in the foci with epithelioid features, as well as MIC2, S100, and NSE. The diagnosis of the lesion was confirmed as Ewing's sarcoma by the presence of the EWS-FLI1 fusion transcript, and could be defined as the so-called "adamantinoma-like Ewing's sarcoma". After wide excision and high-dose chemotherapy with peripheral blood stem cell transfusion, the patient has been well and continuously event-free for 3 years since the initial diagnosis.

Synchronous intracortical adamantinomas with keratin cyst formation

Adamantinoma of the long bones is a rare primary bone tumor of uncertain embryogenesis. It tends to involve the tibia almost exclusively. We report on adamantinomas occurring in a 16-year-old male patient, with synchronous tibial and fibular lesions. Histologically, there were characteristic clusters of epithelial cells in a fibrous background, forming a keratin cyst. Immunohistochemically, these cells were strongly positive for cytokeratin. This keratin cyst formation is quite an unusual finding in classic adamantinoma.

Primary synovial sarcoma of the heart: a cytogenetic and molecular genetic analysis combining RT-PCR and COBRA-FISH of a case with a complex karyotype

Synovial sarcomas usually occur in the soft tissues of the extremities of adolescents and middle-aged patients, in the vicinity of large joints. We present a patient with a synovial sarcoma of the left atrium and ventricle, which is an extremely rare location. Diagnosis was confirmed by reverse transcriptase polymerase chain reaction (RT-PCR), showing the t(X;18) fusion transcript. With a multicolor COmbined Binary RAtio labeling Fluorescence In Situ Hybridization (COBRA-FISH) technique, a complex karyotype evolved with identification of derivative chromosomes with multiplex rearrangements. This underscores the importance of molecular analysis of spindle cell tumors in unusual locations. Moreover, it shows that the presumed diagnostic translocation t(X;18) can be embedded in a sequence of other chromosomal rearrangements of which the function is as yet unknown.