Out of 21 900 cases filed at the Latin-American Registry of Bone Pathology between April 1940 and July 1981, there were 987 with Paget's disease (4.51 per cent); 62 of these (6.28 per cent) were complicated by sarcoma and two were associated with giant-cell tumours of bone (osteoclastoma) without signs of malignancy. There was a slight predominance of men and the ages ranged from 45 to 87 years, with an average of 66 years. The most frequent sites were the femur (23 cases), the humerus (nine), the pelvis (10), and the tibia (nine). The low incidence of vertebral involvement (five cases) is noteworthy and is in sharp contrast to uncomplicated Paget's disease. The most common tumour type was osteosarcoma (39 cases), followed by fibrosarcoma (15 cases); other varieties (chondrosarcoma, malignant fibrous histiocytoma and reticulum-cell sarcoma) were much rarer. Most of the sarcomata occurred when the Paget's disease was polyostotic. Tumours often developed simultaneously, or at short time intervals, in the same or different bones; these bones had, in all cases, been affected by Paget's disease. The histological features of the osteosarcomata were characteristic, with large numbers of osteoclast giant cells, alternating with atypical osteoblasts, thus exaggerating the anarchic remodelling process of Paget's disease. The neighbouring areas of the pagetic bone showed an increased number of osteoclasts. These facts suggest a possible pathogenetic relationship between sarcoma and Paget's disease; the possibility of both processes having a viral aetiology is discussed.

The clinical, radiographic and pathological features of eighty-eight cases of histologically verified intra-osseous ganglia in eighty-three patients are described. All were located in the subchondral bone adjacent to a joint and most frequently involved the hip, the ankle (medial malleolus), the knee and the carpal bones. Forty-seven of the eighty-three patients were male and all the patients were between fourteen and seventy-three years of age, with an average age of forty-one years. There are two fundamental types of intra-osseous ganglia, one apparently arising by penetration of juxta-osseous ganglion into the underlying bone, a mechanism proved in fourteen of our eighty-eight cases (16 per cent); in the remaining seventy-four cases, the ganglion cyst was primarily intra-osseous ("idiopathic"). The initial cause of the intramedullary mucoid degeneration is discussed. We believe that mechanical stress and repeated minor trauma near the surface of the bone may lead to intramedullary vascular disturbance with consequent foci of aseptic bone necrosis. The revitalisation of these areas causes fibroblastic proliferation, followed by mucoid degeneration of the connective tissue, possibly due to some unknown local factor. Curettage or excision is usually effective, and recurrence (only four cases) is exceptional.

A case of intracortical haemangioma in the tibial diaphysis is reported. The radiological and macroscopic features were identical with osteoid osteoma. In view of this similarity, haemangiomata, despite their rarity at this site, must be considered in the differential diagnosis of osteoid osteoma.

The clinical and radiological features in three cases of cystic angiomatosis of bone are reported. Although these features are generally diagnostic except from histiocytosis X, the definitive diagnosis must be established by a pathological study, preferably of a segment of an involved rib or fibula. The prognosis varies according to the type of clinical presentation-in particular upon whether the lesions are solely skeletal or whether there is extraskeletal visceral involvement. Whereas these last cases may often prove fatal, those with only skeletal involvement have a favourable prognosis: indeed, the cystic bone lesions may regress without any treatment, as occurred in some cases reported in the literature and in two of our three cases.

A study of two siblings with a severe infantile form of familial idiopathic hyperphosphatasia is reported. A girl aged one year was followed for two years while receiving intermittent treatment with porcine calcitonin. This induced a clinical remission, a reduction of both the high serum level of alkaline phosphatase and the raised urinary excretion of hydroxyproline, and a remarkable improvement in bone structure as seen radiologically. Her sister aged two months received porcine calcitonin for three weeks, during which clinical improvement, no change in the serum level of alkaline phosphatase and a marked decrease of the excretion of hydroxyproline were recorded.

The features are described of seven cases of "juxtacortical" chondrosarcoma, the term introduced by Jaffe for a rare but distinct entity and now accepted in the World Health Organisation classification as preferable to the term "periosteal" chondrosarcoma. In all cases the lesion involved the shaft of a long bone, most often the femur, and in two cases two different long bones were affected. Six of the seven patients were male and all were in the second decade. The characteristic appearance was that of a small tumour adjacent to the cortex with areas of spotty calcification often accompanied by radiating bone spicules perpendicular to the bone shaft and a typical Codman's triangle. Histologically all the tumours showed a cartilaginous lobular pattern, well limited on the surface and seldom infiltrating the cortex; areas of spotty calcification and enchondral ossification were often present but tumour osteoid and bone were conspicuously absent. Despite the ominous histological aspect, the prognosis proved to be relatively favourable compared with the usual central chondrosarcoma of a similar grade of malignancy.

The clinical, radiographic and pathological features are described of eight cases of a bone tumour which we propose to classify as "malignant osteoblastoma". It presents the characteristics of genuine osteoblastoma but of an aggressive pattern, with more abundant and often plump hyperchromatic nuclei, greater nuclear atypia, and numerous giant cells of osteoclastic type. This rare tumour is regarded as the malignant counterpart of osteoblastoma and appears to be only locally aggressive. It should be separated from conventional osteosarcoma not only because of its peculiar histological pattern, but also because of its different clinical and radiological features and better prognosis. Thus seven of the eight patients were alive and free of disease from one and a half to eleven years after the initial surgical treatment, which in only two cases included amputation. Excision or block resection is the preferred method of treatment.

1. The clinical, radiological and pathological features of 106 cases of eosinophilic granuloma of bone (solitary and multiple) are reported.

2. Our findings support strongly the concept that eosinophilic granuloma, Hand-Schüller-Christian and Letterer-Siwe syndrome are closely related manifestations of a single pathological disorder, characterised fundamentally by the proliferation of non-neoplastic histiocytes, intermingled with a variable amount of eosinophilic leucocytes and other inflammatory elements.

3. Lipid-bearing histiocytes (xanthoma cells) may be found in variable amounts in solitary and multiple lesions but are more abundant in the more extensive or chronic lesions of Hand-Schüller-Christian syndrome.

4. These entities may perhaps represent some type of immuno-allergic (hypersensitive) reaction to a still unknown infection, possibly viral.

1. A series of thirty-two cases of chondromyxoid fibroma is reported.

2. The clinical, radiographic and pathological features are described.

3. The rarity of the tumour and of malignant change is stressed.

4. Excision or block resection is preferred to curettage as a method of treatment, because of the liability to recurrence after curettage.

5. It is suggested that the designation "fibromyxoid chondroma" is more appropriate than the usual designation "chondromyxoid fibroma".

1. A clinical, radiological and pathological study of sixty-nine cases of epiphysial chondroblastoma has been made.

2. The nature of the tumour is discussed and its clinical and radiographic features are described. A special type is described, for which the name "cystic chondroblastoma" is suggested.

3. The results of treatment are described and the generally benign behaviourof the lesion is noted.

4. The occurrence of malignant change is noted and discussed.

A case of unusually extensive pigmented villonodular synovitis of the wrist with involvement of bone, particularly of the distal end of the radius, is reported. The clinical and radiographic evidence suggested a diagnosis of primary bone tumour, possibly a giant-cell tumour with sarcomatous transformation.

1. Histochemical studies have been made of the distribution of alkaline phosphatase, glycogen and acid mucopolysaccharides in normal growing bones (mice, rats and men) and also in forty cases of pathological bone processes (neoplastic and dystrophic).

2. The study of normal material confirmed that alkaline phosphatase is plentiful in calcification of cartilage and even more plentiful in bone formation (whether enchondral or direct).

3. It was observed that glycogen increased in the cartilage areas about to be calcified, and that it disappeared in those calcified. It seemed that osteoblasts did not always contain glycogen.

4. In the pathological material (tumours and dystrophic processes) there was great phosphatase activity in the osteogenic areas and also in the cartilage about to be calcified. Whereas glycogen was plentiful in some cases of neoplastic or reactive osteogenesis, it was absent from others.

5. In every area of normal or pathological ossification, the presence of phosphatase seems to be a rule; glycogen is often but not always present.

6. It appears that alkaline phosphatase plays an important role in the formation of the protein matrix of bone, but is not associated with the elaboration of the mucoprotein cartilage matrix.

We believe it is premature to draw any definite conclusion on the behaviour and role of the metachromatic substances in the processes of calcification and ossification.

The histochemical study of alkaline phosphatase has shown that this is a valuable method in the detection of reactionary or pathological osteogenic processes which in some cases are difficult to demonstrate with the usual histological methods.

Osteoarthritis, as seen in the hip, is a disease which eventually embraces all the tissues of the joint but begins as a reaction of the juxta-chondral blood vessels to a degeneration of the articular cartilage; this reaction results in a hyperaemia of the bone. To our surprise we found that daily use preserves rather than "wears out" articular cartilage; indeed inadequate use is the commonest cause of cartilage degeneration and ensuing vascular invasion. To this factor are added the effects of excessive pressure in the many patients who require surgical treatment for advanced osteoarthritis of a hip the seat of some anatomical incongruity. This etiology based on cartilage suffering does not exclude, but indeed explains, the osteoarthritis implanted on joints of a normal shape which have been previously affected by acute or chronic inflammation or by hormonal dysfunction, such as acromegalic osteoarthritis. The stimulus to vessel growth and invasion is the same in all these cases—namely cartilage damage. Once the vessels have entered the cartilage the bone and marrow of the osteophyte are inevitably laid down. What is so damaging in osteoarthritis seems to be not the degeneration of the cartilage but the vigorous and persistent attempt at repair, an attempt which aggravates the already disordered function of the joint not only by osteophyte formation but by the hypervascularity which weakens the structure of the bone beyond the point where it can carry its increased load. The collapse that follows provokes further reparative efforts with the same deplorable results. The osteoarthritic process thus appears to be an attempt to transform a decaying joint into a youthful one and for this, as in the miraculous rejuvenation depicted in Goethe's Faust, a high price must ultimately be paid.

1. Primary reticulum-cell sarcoma of bone arises from the reticulo-histiocytic elements of bone marrow.

2. The authors have studied ten cases of primary reticulum-cell sarcoma of bone, and have compared the clinical, pathological and radiographic features with those of thirty-five cases of Ewing's sarcoma.

3. In their microscopic studies Hortega's staining techniques were used in addition to orthodox methods.

4. There are histological differences between a reticulum-cell sarcoma and Ewing's sarcoma.

5. Certain clinical and radiographic features help the differentiation between the two tumours.

6. The progress and treatment of the reticulum-cell sarcoma are reviewed in detail.