Pelvic aneurysmal bone cyst

This paper describes an extremely rare case of a huge aneurysmal bone cyst (ABC) in the pelvis, occurring in the patient's 5(th) decade of life. The patient presented with a history of painless huge pelvic mass for 10 years. Plain radiograph and computed tomography showed huge expansile lytic lesion arising from the right iliac bone. A biopsy was performed and histology confirmed diagnosis of aneurysmal bone cyst. Unfortunately, the patient succumbed to profuse bleeding from the tumour.     

Fibromyxoid areas and immature osteoid are associated with recurrence of primary aneurysmal bone cysts

AIMS: Primary aneurysmal bone cysts have a high recurrence rate following curettage. The aim of this study was to determine clinicopathological features associated with recurrence of aneurysmal bone cysts. METHODS AND RESULTS: The clinicopathological features of 86 patients (37 males, 49 females, age range 5-62 years) with aneurysmal bone cysts were reviewed. Recurrence rates following curettage and excision were 32.7% and 5.6%, respectively (P = 0.028). The association of clinicopathological features with recurrence was studied in a subset of 45 patients treated by curettage. The presence of nodular fasciitis-like fibromyxoid areas [P = 0.033, odds ratio (OR) = 9.17, 95% confidence interval (CI) 1.06, 79.39] and immature osteoid with active osteoblasts (P = 0.041, OR = 3.7, 95% CI 1.03, 13.35) was significantly associated with an increased risk of recurrence. Clinical and radiological features were not associated with recurrence. In a multivariate analysis, the presence of immature osteoid was a better predictor of recurrence than radiological activity (hazard ratio = 3.18, 95% CI 1.04, 9.73, P = 0.043). There was no statistically significant association between radiological activity and histological features. CONCLUSIONS: Aneurysmal bone cysts with nodular fasciitis-like fibromyxoid areas and immature osteoid with active osteoblasts are more likely to recur. Mention of these features in histopathology reports will help to identify patients who require closer follow-up. Lesions that are apparently radiologically inactive may show fibroblastic and osteoblastic proliferation and therefore may recur.     

Primary aneurysmal cyst of soft tissue

We report a case of primary aneurysmal cyst of soft tissues in a 57-year-old woman presenting with a painful mass in her left arm. Conventional radiography showed a radiolucent soft tissue mass surrounded by a ring of bone. MRI displayed an unusual, ill-defined soft tissue lesion that was not connected to the nearby humerus and appeared to be an aggressive tumour. Microscopically, the mass consisted of multiple anastomosing cavernous channels surrounded by a peripheral band of mature trabecular bone. These bloody channels were separated by fibrous septa containing fibroblasts, histiocytes and multinucleated giant cells, as well as fibromyxochondroid material. Some of these giant cells lined the septa and partially occupied the lumen of the channels. Ultrastructurally, the features observed in this tumour were similar to those described in aneurysmal bone cyst; the giant cells lining the septa were an additional observation. Whereas most bone tumours have a well-known extraosseous counterpart, this unique lesion is not well recognized by surgical pathologists and the few published cases have been reported under different names. Gross, microscopic, radiological and ultrastructural findings are presented to familiarize pathologists with this underdiagnosed condition.     

Primary aneurysmal bone cyst of the mandibular condyle with USP6-CDH11 fusion

Primary aneurysmal bone cyst (ABC) is a cystic bone neoplasm characterized by disease-defining gene fusions involving the USP6/Tre2 gene. The literature describing gnathic ABC is limited. This case report describes a 27-year-old man presenting with a long-standing left-sided facial asymmetry. Multi-detector computed tomography imaging demonstrated a large expansile lesion positioned within the left condylar head. The lesion was biopsied and resected. The specimen showed a giant cell-rich cystic neoplasm, with fibrous tissue lined by multinucleated giant cells. Next-generation sequencing confirmed the presence of a USP6-CDH11 fusion gene, consistent with classification as a primary ABC, the first reported to be translocation-positive in the head of the mandibular condyle.     

Pathologic evaluation of the solid variant of aneurysmal bone cysts with USP6 rearrangement with an emphasis on the frequent diagnostic pitfalls

The solid variant of aneurysmal bone cyst (SVABC) is very uncommon and frequently misdiagnosed. We reevaluated and summarized the clinicopathologic features of 17 SVABCs and further discussed the use of this nomenclature to differ SVABCs from extragnathic giant cell reparative granuloma (GCRG) in the setting of the USP6 rearrangement era. The immunohistochemical markers included α‐SMA, SATB2, AE1/AE3, Ki67, S100, CD68 and P63. USP‐6 status was detected by fluorescence in situ hybridization using a break‐apart probe. The 17 patients with SVABCs comprised 10 males and 7 females ranging in age from 4 to 70 years. The involved locations included the long bone (n = 11), hand (n = 4), rib (n = 1) and vertebra (n = 1). The lesions were characterized by proliferated spindle cells with scattered giant cells and hemorrhages with variable positive α‐SMA, SATB2, CD68 and Ki‐67 expression. All patients had USP6 rearrangements without H3F3A glycine 34 mutations. Our study reveals that SVABC shares similar clinical and histologic features with other bone lesions, which may lead to an erroneous diagnosis. The presence of an USP‐6 rearrangement contributes to the diagnosis SVABC; SVABC and most of the previously documented extragnathic GCRGs may be considered within the umbrella of primary aneurysmal bone cysts.     

Latent form of multiple dermoid cysts in the jaw bone

Dermoid cysts of the jaw are exceedingly rare, and only six such cases have been documented. The present paper reports a case with multiple microcysts showing histological characteristics of dermoid cyst in the surgically resected mandibular bone. These cysts were located near the inferior border of the mandibular bone, and histologically composed of an inner thin layer of squamous epithelium with marked hyperorthokeratinization and an outer layer of fibrous tissue containing numerous mature sebaceous glands. In addition, a hair follicle-like epithelial sphere was seen in part. The present microcysts suggest that it arises de novo, and one possible cause of jaw cysts could be sequestration of the stomadeal ectoderm that may have been trapped deep in the surface and embedded in the developing mandibular bone during embryogenesis. It may not be possible that such cysts developed from the odontogenic epithelial remnant undergoing dermoid metaplasia.     

Solid variant of aneurysmal bone cyst: a case report with bilateral involvement of the distal femoral metaphyses

An extremely rare case of bilateral, symmetrical involvement of distal femoral metaphyses by the solid variant of aneurysmal bone cyst (ABC) in a boy aged 13 years is described. Although there is no difference between the conventional ABC and the solid variant in terms of clinical and radiological presentation, the lesion is solid, composed of fibrohistiocytic cells with abundant giant cells and/or areas of florid, heterotopic ossification, while aneurysmal channels are sparse or absent. The lesion needs to be differentiated from giant cell tumour of bone, when the osteoclastic component predominates, while fibrous dysplasia, osteoblastoma and even osteosarcoma need to be excluded any time ossification is prominent. Careful evalution of the clinical, radiological and pathological findings is necessary.     

Aneurysmal bone cyst,a study of ultrastructure and malignant transformation

Summary Four cases of aneurysmal bone cyst, of which one became malignant 7 years after irradiation, were studied by electron microscopy. The aneurysmal bone cyst was composed of four different types of stromal cells — fibroblasts, myofibroblasts, osteoblasts, and histiocytes — and osteo-clastlike multinucleated giant cells. The surface of blood spaces was devoid of specialized endothelium, which may explain the presence of large quantities of extravasated erythrocytes. Some histiocytes contained siderosomes. The malignant lesion consisted of two main types of stromal cells, of which one had electron lucent and the other electron dense cytoplasm. The stromal cells produced osteoid and the tumour was regarded as an osteosarcoma. The multinucleated giant cells resembled those observed in aneurysmal bone cysts, but the nuclei seemed to be more often spherical. It is concluded that irradiation of the aneurysmal bone cyst may cause sarcomatous transformation in a cell capable of producing osteoid.     

Dedifferentiated low-grade central osteosarcoma with extensive cystic change initially treated as a simple bone cyst

Low-grade central osteosarcoma (LG-COS) is an uncommon variant of osteosarcoma (OS) that sometimes progresses to high-grade OS post-recurrence. We herein present a case of dedifferentiated LG-COS with extensive cystic change arising in the right iliac bone of a 26-year-old man. The LG-COS was initially diagnosed and managed as a simple bone cyst. The lesion recurred thrice, and high-grade OS was diagnosed during the third recurrence. The first lesion appeared as a typical benign cystic mass on radiography. However, a huge malignant osteoblastic mass subsequently developed in the right pelvis at the third recurrence. Extended hemipelvectomy with ipsilateral hemisacral resection was performed. Histologic analysis showed tumor necrosis and irregular neoplastic tumor osteoid, while immunohistochemistry revealed that the tumor was diffusely positive for MDM2 and CDK4. The histologic diagnosis was high-grade OS dedifferentiated from a preceding cystic lesion. Our final diagnosis of the primary lesion was LG-COS with extensive cystic change.     

骨膜下动脉瘤性骨囊肿的临床病理特征

目的探讨骨膜下动脉瘤性骨囊肿（subperiosteal aneurysmal bonecyst,SABC）的临床病理学特征。方法报道2例SABC并回顾性分析27例文献检索资料。结果例1,女性,17岁,右股骨干骨膜下多囊性肿块,内见液一液平,表面骨壳包绕,有骨膜反应。例2,女性,23岁,右肱骨干-干骺部骨膜下肿块,为低密度影,有薄层骨壳包绕。2例镜下均见含血囊腔结构及结缔组织性的隔,由纤维母细胞、破骨细胞样多核巨细胞及反应性新骨构成。结论SABC为罕见病变,好发于女性,通常位于长骨干骨膜下,影像学上常见病变周反应性骨壳形成及骨膜反应,组织学形态特征与普通动脉瘤性骨囊肿相同,术后不易复发。     

A novel t(6;13)(q15;q34) translocation in a giant cell reparative granuloma (solid aneurysmal bone cyst)

Aneurysmal bone cyst is a rapidly growing and locally aggressive lesion that commonly affects children and young adults. Initially regarded as a reactive process, primary aneurysmal bone cyst is now widely accepted as a neoplasm owing to recent findings of recurrent clonal chromosomal alterations, mostly t(16;17)(q22;p13). However, other infrequent chromosomal rearrangements have also been reported. Giant cell reparative granuloma, previously regarded as a nonneoplastic process and histologically indistinguishable from the solid variant of aneurysmal bone cyst, is frequently seen in the gnathic bones and the short tubular bones of the hands and feet. Here we present such a case of giant cell reparative granuloma (solid aneurysmal bone cyst) in the finger of a 63-year-old white man. Cytogenetic analysis revealed a novel alteration involving a reciprocal translocation between 6q and 13q, with a karyotype of 46,XY,t(6;13)(q15;q34),del(20)(q13.1).     

Aneurysmal bone cyst and telangiectatic osteosarcoma

Summary In a series of 105 cases of aneurysmal bone cyst, 18 showed an unusually high level of mitotic activity and/or increased nuclear pleomorphism which complicated the differential diagnosis with respect to telangiectatic osteosarcoma. An attempt was made to use semi-automatized morphometric and histophotometric techniques to establish objective morphological differences between these unusual cases of aneurysmal bone cyst and 16 cases of telangiectatic osteosarcoma. Three cases (two of aneurysmal bone cyst and one of telangiectatic osteosarcoma) proved unsuitable for analysis. In 24 of the remaining 31 cases (77%) a computerized discriminant analysis permitted correct discrimination with a high degree of certainty on the basis of quantitative nuclear characteristics determined in paraffin sections. In the other 7 cases the diagnosis was less certain (3), doubtful (2) or erroneous (2). The relevant nuclear characteristics were (in ascending sequence of discrimination): the largest nuclear surface area, the mitotic index, and the percentage of nuclear sections exceeding an arbitrarily chosen limit of 60 ².The criterion of nuclear size for discrimination between these benign and malignant lesions could be applied for two reasons: firstly, because a group of extremely large nuclei occur in malignant cases, and secondly, because the average nuclear size is larger in malignant than in benign lesions. The extremely large nuclei occur as only a small percentage of the total nuclear population. The other variables investigated, i.e., cellularity and nuclear contour ratio, did not contribute greatly to the differentiation. In 11 cases, the average nuclear Feulgen extinction was estimated as an additional variable.     

髌骨软骨母细胞瘤临床诊疗经验并文献复习

目的 探讨髌骨软骨母细胞瘤的临床诊断、鉴别及治疗方法并对相关文献进行复习,以增强对此病的认识和理解。方法 报道华中科技大学同济医学院附属同济医院2014年7月至2022年1月收治的髌骨软骨母细胞瘤患者3例,对患者进行病史采集、体格检查及影像学扫描,发现髌骨内呈单囊性或多囊性膨胀性骨破坏表现,完善术前检查后行髌骨病变囊内刮除、囊壁电烧并异体/自体骨植骨手术,其中1例因病理性骨折行克氏针内固定并“8”字钢丝捆扎。结果 术后病理诊断皆为髌骨软骨母细胞瘤,其中1例合并动脉瘤样骨囊肿并病理性骨折。术后患者伤口皆愈合良好,内固定稳定,随访期间关节活动度良好,行走负重无不适,无复发。结论 髌骨软骨母细胞瘤的发生率极低,若合并动脉瘤样骨囊肿,则诊断难度增大,容易误诊,需要结合临床检查、影像学资料、病理学会诊等综合评估,治疗方法为打通、彻底刮除囊腔内病变肿瘤组织、电烧囊壁并充分植骨。     

Fine-needle aspiration biopsy of solid aneurysmal bone cyst in the humerus

We report the fine-needle aspiration biopsy (FNAB) cytology findings of a solid aneurysmal bone cyst in the left humerus of a 69-yr-old woman. Radiographically, the lesion showed an extensive, relatively well-defined osteolysis in the diaphysis, with a pathologic fracture. FNAB smears of the lesion consisted of benign, mononuclear cells and numerous osteoclast-like multinucleated giant cells. Some clusters of the mononuclear cells were closely associated with dense, homogeneous, extracellular, matrix material. To our knowledge, the FNAB features of solid ABC of the long bones have not been described previously in the English-language literature. The cytologic features are indistinguishable from those of giant cell tumors of bone and brown tumors of hyperparathyroidism.     

Calcifying solitary bone cyst: morphological aspects and differential diagnosis of sclerotic bone tumours

Fourteen solitary bone cysts (SBC) with large areas of calcification (7 in the femur, 4 in the humerus, and 1 each in the pelvis, the tibia and the scapula) and 402 SBC from the Hamburg Bone Tumour Registry were reviewed in a retrospective study. The analysis was done with emphasis on the clinical, radiological and histological appearances. SBC are well known lesions, but calcifying SBC (CSBC) or extensive extragnathic cement-like bone productions are rare. The clinical and radiological differential diagnosis includes fibrous dysplasia, chondroma, low-grade chondrosarcoma and osteosarcoma. Bits of this cement-like matrix are detectable within the wall of approximately 70% (278 of 402) of SBC from the registry. CSBC are changed SBC. The intraoperative confirmation of the diagnosis on a frozen section by the bone pathologist leads to curettage which is currently the most common therapy in this benign lesion.     

Tiling resolution array-CGH shows that somatic mosaic deletion of the EXT gene is causative in EXT gene mutation negative multiple osteochondromas patients

Multiple osteochondromas (MO) is a hereditary skeletal disorder characterized by the presence of cartilage capped bony outgrowths at bone surface. Causative mutations in EXT1 or EXT2 genes have been described in 85-90 % of MO cases. However, in about 10-15 % of the MO cases, genomic alterations can not be detected, implying the potential role of other alterations. We have designed a custom-made Agilent oligonucleotide-based microarray, containing 44,000 probes, with tiling coverage of EXT1/2 genes and addition of 68 genes involved in heparan sulfate biosynthesis and other related pathways. Out of the 17 patient samples with previously undetected mutations, a low level of deletion of the EXT1 gene in about 10-15% of the blood cells was detected in two patients and mosaic deletion of the EXT2 was detected in one patient. Here we show that for the first time somatic mosaicism with large genomic deletions as the underlying mechanism in MO formation was identified. We propose that the existence of mosaic mutations and not alterations of other heparan sulfate biosynthesis related genes play a significant role in the development of MO in patients who are tested negative for mutations in Exostosins.     

Reversed clinical phenotype due to a microduplication of Sotos syndrome region detected by array CGH: microcephaly, developmental delay and delayed bone age

Haploinsufficiency of the NSD1 gene due to 5q35 microdeletions or intragenic mutations is the major cause of Sotos syndrome characterized by generalized overgrowth, large hands and feet with advanced bone age, craniofacial dysmorphic features, learning disability, and possible susceptibility to tumors. Here, we report on a 14-month-old boy with a reverse phenotype of Sotos syndrome due to the reciprocal duplication of the 5q35.3 region, including the NSD1 gene, detected by array CGH. The phenotype includes delayed bone age, microcephaly, seizures, and failure to thrive. Our case suggests that the gene dosage effect of the NSD1 gene is the likely cause for the reversed phenotype of Sotos syndrome in this patient.