S. Fiona Bonar

An unusual variant of intraneural ganglion of the common peroneal nerve

A highly unusual variant of an intraneural ganglion of the common peroneal nerve in a 30-year-old male is presented. There was extrusion of the contents of the cyst into the substance of the nerve, dissecting between the fibres and expanding the nerve in such a way that it mimicked an intraneural tumour clinically, radiologically and histologically. A comprehensive review of the entity is undertaken.

Parachordoma is not distinguishable from axial chordoma using immunohistochemistry

Parachordoma is a rare soft tissue tumor that morphologically resembles chordoma of the axial skeleton but occurs in a peripheral site. A recent study reported immunohistochemical differences between chordoma and parachordoma. While both tumors were positive for cytokeratin (CK) 8/18 (as recognized by the antibody Cam5.2), S100 and epithelial membrane antigen (EMA), only the chordoma was positive for CK7, CK20, CK 1/5/10/14 (as recognized by the antibody 34βE12) and carcinoembryonic antigen (CEA). It has since been suggested that tumors indistinguishable from chordoma that involve the periphery should be termed chordoma periphericum and that these tumors are distinct from parachordoma. In the current study, the clinical, radiological, pathological, immunohistochemical and ultrastructural features of a chordoma‐like tumor involving the deep soft tissues of the lower leg of a 69‐year‐old woman are presented. Microscopically, the tumor had a pseudolobulated growth pattern and consisted of sheets, nests and cords of epithelioid cells, some with a physaliferous appearance, separated by abundant myxoid stroma. The tumor cells were positive for CK 8/18, EMA and S100, showed focal staining for CK7, and were negative for CK20, CK 1/5/10/14 and CEA. On the basis of these results a diagnosis of parachordoma was favored. For comparison, an immunohistochemical analysis of five axial chordomas was also performed. The chordomas showed positivity for CK 8/18 (5 of 5 cases), EMA (5 of 5 cases), S100 (5 of 5 cases), CK 1/5/10/14 (1 of 5 cases) and CK7 (1 of 5 cases). Stains for CK20 and CEA were negative in all five chordomas. The results of the present study suggest that the expression of antigens for CK 1/5/10/14, CK7, CK20 and CEA in chordoma might not be as common as what has been previously reported. The results also suggest that parachordoma might not be easily distinguished immunohistochemically from axial chordoma (and therefore also from so‐called chordoma periphericum).

Periprosthetic Tissues From Third Generation Alumina-on-Alumina Total Hip Arthroplasties

The histological features of periprosthetic tissues are related to the bioreactivity of particles generated by the prosthesis. This study analyzed synovial-like pseudocapsules collected from 21 patients with alumina ceramic-on-ceramic hip arthroplasties and correlated histological features with wear of the ceramic bearings, duration of implantation and clinical factors such as neck-to-rim impingement. A histopathological classification system was developed for this purpose. The pseudocapsules were viable, with few foreign body type giant cells and occasional lymphocytes. This differs from tissues in polyethylene containing hip arthroplasties which often have extensive foreign body type inflammatory changes or from metal-on-metal hip arthroplasties in which extensive necrosis is common. Soft-tissue inflammation was not associated with failure of the hip arthroplasties, and may be clinically insignificant in alumina-on-alumina total hip arthroplasties.

Intramuscular dendritic fibromyxolipoma: Myxoid variant of spindle cell lipoma?

Dendritic fibromyxolipoma (DFML) is an uncommon, recently described, benign soft tissue lesion that shares many clinical and pathological features with myxoid variants of spindle cell lipoma (SCL). As described, DFML is distinguished from SCL by the presence of dendritic cytoplasmic processes, abundant keloidal collagen and a prominent, often plexiform vascular pattern. We describe the first known reported case of an intramuscular DFML that occurred in the right shoulder region of a 73‐year‐old man. The tumor displayed the typical histopathological features of DFML but also included foci of chondroid metaplasia, a previously unreported finding. This report also discusses the differential diagnosis, particularly distinguishing DFML from SCL and myxoid liposarcoma. In view of the similarities in many clinical and pathological features between SCL and DFML, we speculate that DFML probably represents an unusual variant of myxoid SCL.

Epithelioid and spindle cell haemangioma of bone

A case of epithelioid and spindle cell haemangioma of bone occurring in the proximal femur is presented. The tumour had typical microscopic features with a striking lobular pattern comprising spindled and epithelioid areas with admixed inflammatory cells. The case represents only the eighth reported example of this rare tumour, which appears to fit in the spectrum of epithelioid haemangioma. This is the first case to involve the proximal portion of a long bone. A review of the classification and features of similar vascular tumours of bone is presented.

Intraosseous hibernoma: characterization of five cases and literature review

ObjectiveTo describe the imaging and histopathological findings and provide an overview of a recently described and rare cause of bone sclerosis.Materials and methodsFive cases of intra-osseous hibernoma of bone that presented over the last year. The imaging and histopathology is reviewed.ResultsAll cases were identified in asymptomatic middle-aged to elderly adults as incidental findings with bone sclerosis in the axial skeleton. MRI showed lesions that were T1 hypointense to subcutaneous fat and hyperintense to skeletal muscle and one showed contrast enhancement. Glucose avidity was demonstrated on FDGPET in both cases tested and isotope bone scan performed in three cases showed strong positivity in two, but uptake was inconspicuous in one case.ConclusionsIntra-osseous hibernoma is a rare cause of sclerotic bone lesions, predominating in the axial skeleton of middle-aged and elderly adults. They have a non-aggressive appearance on CT and on MRI are T1 hypointense to subcutaneous fat and hyperintense to skeletal muscle. They are usually T2 hyperintense and may show peripheral contrast enhancement. They may show increased glucose avidity on FDGPET and may or may not be positive on isotope bone scans. We suspect that with ever-increasing use of a variety of imaging techniques, particularly in a setting of staging for malignant disease, more such cases will come to light. This diagnosis should be added to the differential diagnosis of sclerotic bone lesions.

Central low-grade osteosarcoma: a diagnostic challenge

This is an overview of the diagnostic challenges in central low-grade osteosarcoma with discussion of recent molecular data, which are of help in resolution of the diagnosis. The designation “low-grade osteosarcoma” usually encompasses surface low-grade or parosteal osteosarcoma and central or intramedullary low-grade osteosarcoma. Rare cases of low-grade osteosarcoma of soft tissues are documented [1]. Low grade central osteosarcoma, first described in 1977 [2], is an uncommon but well-recognised variant of osteosarcoma responsible for approximately 1% of all osteosarcomas. Male and female subjects are equally affected and it afflicts a slightly older age group than conventional osteosarcoma, most individuals being in the second and third decades with an age range from 9 to 83. Any bone may be affected, but there is a strong predilection for the long bones, particularly the femur and tibia, around the knee [3]. Recently characterisation of involvement of gnathic bones has been documented [4]. Most patients complain of pain, fewer complaining of pain and swelling. About 10% have a mass and occasional cases are asymptomatic. The duration of symptoms varies from 2 weeks to 5 years, most occurring over several months. Tumour size varies from 2 to 25 cm, with an average size of 9 to 10 cm. Fewer than 10% measure less than 5 cm [3]. Low-grade central osteosarcoma is characterised by a significantly better prognosis than conventional osteosarcoma, exhibiting slow growth, low metastatic rate, and prolonged survival after adequate treatment. The recommended treatment is that of wide local excision or amputation, after which recurrence is unusual. Curettage or marginal excision inevitably results in recurrence. Transformation into a high-grade form occurs more commonly in these circumstances and several individuals who have had multiple biopsies performed over time prior to diagnosis have shown transformation to a high-grade tumour with consequent higher mortality [2, 3, 5]. Occasional cases with dedifferentiation at diagnosis are documented [6].

The Role of Intra-operative Pathological Evaluation in the Management of Musculoskeletal Tumours

A tissue biopsy is usually a critical aspect in guiding appropriate initial management in patients with musculoskeletal tumours. We have previously outlined the role of intra-operative frozen section in both the determination of adequacy of a biopsy and for its diagnostic utility. In this article, the options and techniques for intra-operative pathological evaluation, namely frozen section, fine needle aspiration cytology and touch imprint cytology are reviewed. Frozen section examination may be applicable in the following Sections, including (1) at core biopsy, (2) at surgical margins, (3) at confirming diagnosis prior to definitive treatment or to evaluate tumour spread, and (4) at establishing a diagnosis of a metastasis prior to intramedullary nailing. There are also situations in which frozen section is inappropriate. Pitfalls associated with frozen sections are also highlighted. There are also cost implications, which we have quantified, of performing frozen sections. In our experience that the use of intra-operative pathological evaluation reduces the non-diagnostic rate of bone and soft tissue sarcoma biopsies, eliminates the need for re-biopsy hence alleviating stress, and is a useful addition to the armamentarium in evaluating musculoskeletal tumours.

Thalidomide and neurotrophism

BackgroundFollowing the thalidomide disaster (1958–62), Henkel and Willert analysed the pattern of dysmelia in the long bones (J Bone Joint Surg Br. 51:399–414, 1969) and the extremities, Willert and Henkel (Z Orthop Ihre Grenzgeb. 107:663–75, 1970). Willert’s material from deformed extremities is re-examined here asking “How does thalidomide reduce the skeleton?”Materials and methodsWe reviewed the original data collection of Willert and Henkel (Z Orthop Ihre Grenzgeb. 107:663–75, 1970), comprising musculoskeletal histology slides from 30 children affected by thalidomide with radiographs of hands (19 cases) and feet (4 cases).ResultsAll original observations by Willert and Henkel (Z Orthop Ihre Grenzgeb. 107:663–75, 1970), were verified. Radial rays of the hand disappeared early, but the foot was spared until late. Radiology confirms that bone reduction in the hand (aplasia or hypoplasia in the thumb and index finger) coincides with sensory segmental nerve C6. In the foot, reduction of the toes is rare, but mesenchymal excess (polydactyly) occurs in the hallux (L5 sclerotome), usually associated with absent tibia (L4 sclerotome). Histology confirms skeletal mesenchymal components to be unremarkable, contrasting with grossly abnormal bony architecture, a striking discordance between microscopic and macroscopic findings. No necrosis or vascular pathology was seen.ConclusionThe basic lesion was an abnormal quantity rather than quality of mesenchyme. Cell populations result from cellular proliferation, controlled in early limb bud formation by neurotrophism. Thalidomide is a known sensory neurotoxin in adults. In the embryo, sensorineural injury alters neurotrophism, causing increased or diminished cell proliferation in undifferentiated mesenchyme. Differentiation into normal cartilage occurs later, but within an altered mesenchymal mass. Reduction or excess deformity results, with normal histology, a significant finding. The primary pathological condition is not in the skeleton, but in the nerves.

Clinical, cellular, microscopic, and ultrastructural studies of a case of fibrogenesis imperfecta ossium.

Fibrogenesis imperfecta ossium is a rare disorder of bone usually characterized by marked osteopenia and associated with variable osteoporosis and osteosclerosis, changing over time. Histological examination shows that newly formed collagen is abnormal, lacking birefringence when examined by polarized light. The case presented demonstrates these features and, in addition, a previously undocumented finding of a persistent marked reduction of the serum C3 and C4. Osteoblasts established in culture from a bone biopsy showed abnormal morphology on electron microscopy and increased proliferation when cultured with benzoylbenzoyl-ATP and 1,25-dihydroxyvitamin D, contrasting with findings in normal osteoblasts in culture. A gene microarray study showed marked upregulation of the messenger RNA (mRNA) for G-protein-coupled receptor 128 (GPR 128), an orphan receptor of unknown function and also of osteoprotegerin in the patient’s osteoblasts in culture. When normal osteoblasts were cultured with the patient’s serum, there was marked upregulation of the mRNA for aquaporin 1. A single pathogenetic factor to account for the features of this disorder has not been defined, but the unique findings described here may facilitate more definitive investigation of the abnormal bone cell function.