Intravascular fibrin thrombi and endothelial cell damage in central giant cell granuloma.

Two cases of central giant cell granuloma were studied ultrastructurally. The majority of vessels showed intravascular fibrin thrombi and endothelial cell damage, with gaps in their walls. Plasma, red cells and fibrin were seen subendothelially. The basal lamina was absent from endothelial cells where these components were in contact with their plasma membrane; otherwise it showed multiplication. It is suggested that the absence of basal lamina is the result of degeneration and that these vessels are probably venules and capillaries rather than lymphatics. Myofibroblasts were the dominant stromal cells. Giant cells had little phagocytic activity. It seems that the main function for the stromal cells is the repair of the haematoma and the damaged vessels. It is proposed that the term giant cell reparative granuloma is appropriate, but it should not be used indiscriminately for all jaw lesions containing giant cells.

Ultrastructural finding of vascular degeneration in fibrodysplasia ossificans progressiva (FOP).

The masseter and temporalis muscles were investigated ultrastructurally in 2 patients having fibrodysplasia ossificans progressiva (FOP). Results showed atrophy and necrosis of muscle fibres. Both cases contained cartilage which was calcified in the second case and was associated with degenerating chondrocytes. The blood vessels showed various changes, with haematoma formation and large fibrin deposits. Some of the fibrin deposits seen in the second case were surrounded with cartilage. This suggests that the cartilage probably forms as a reaction to an old haemorrhage. It is possible that the effect of the mutant gene found in FOP is on blood vessels rather than the normal regulatory mechanisms of the inducible osteogenic precursor cells. These degenerating blood vessels often result in haemorrhage and fibrin deposits; the fibrosis, cartilage or bone formation are probably secondary changes. Amianthoid fibres found in the tendon of the temporalis muscles of the second case, together with the other changes of fibrosis and cartilage formation, account for the severe restricted mouth opening suffered by these patients.

Ultrastructural finding of vascular degeneration in myositis ossificans circumscripta (fibrodysplasia ossificans).

A case of myositis ossificans circumscripta (fibrodysplasia ossificans) of the masseter muscle has been studied ultrastructurally. It showed atrophy of muscle fibres with deranged myofilaments, adjacent to dense fibrous tissue, osteoid and bone. A large number of the cells found in the dense fibrous tissue showed vacuolation and separation of membrane bound vesicles similar to matrix vesicles released by chondroblasts and osteoblasts during calcification. It is possible that, as in normal calcification of bone, these vesicles are responsible for initiating calcification in the ectopic bone found in the present condition. It was also shown that most of the blood vessel found in the blocks examined exhibited various degrees of degenerative changes. The finding of arterial occlusion together with capillary degeneration suggests that the main changes in myositis ossificans circumscripta may be those affecting blood vessels leading to ischaemic muscle atrophy. The fibrosis and ossification that follow are probably secondary changes.

The nature of the eosinophilic and laminated masses in the adenomatoid odontogenic tumor: a histochemical and ultrastructural study.

The eosinophilic and laminated masses in AOT were investigated with the light and electron microscope in two cases. The results showed that the eosinophilic amorphous masses were heterogenous and consisted mainly of three types of fibrils. These were: thin collagen, electron dense fibrils probably resulting from degradation of collagen and masses of amyloid filaments with or without collagen fibers in normal and degraded forms. In addition some of the eosinophilic deposits resulted from changes surrounding blood vessels which led to deposition of either collagen or fine filaments arranged into layers around these vessels. In all these areas there was a peripheral layer of fine filaments perpendicular to the epithelial basal lamina, similar to that found in early dentin formation. This layer may be responsible for the reticulin staining found in this tumor. On the other hand the great majority of the laminated masses represented calcified amyloid with or without areas of calcified degraded collagen which were indistinguishable from amyloid. The results suggest that the various fibrils forming the eosinophilic masses in AOT are probably related and may be the result of changes in blood vessels. They also revealed that calcification involves mainly amyloid.

Permanent teeth in hypophosphatasia: light and electron microscopic study.

The changes in a permanent central incisor of a patient suffering from hypophosphatasia, were investigated light microscopically and compared with those of two of his primary teeth. In addition his other central incisor was studied with transmission and scanning EM. The changes in permanent teeth were similar to those of the primary dentition, including loss of cementum and the presence of deep resorption areas in dentin. Afibrillar cementum was detected with EM, and was attached to dentin surface. The presence of a thick layer of bacterial plaque was a prominent feature in all the teeth examined. A large number of bacteria was also found in resorption bays. It is suggested that bacteria may play an important role in the destruction of soft and hard tissues leading to loss of teeth in hypophosphatasia.

A comparative stereologic and ultrastructural study of blood vessels in odontogenic keratocysts and dentigerous cysts.

Blood vessels were investigated both stereologically and ultrastructurally in keratocyst and dentigerous cyst. The volume and surface densities of blood vessels in 15 keratocysts and dentigerous cysts were analyzed stereologically. No significant differences were found between them using these parameters, suggesting that their overall vascularity may be similar. However, the ultrastructural study showed marked differences between blood vessels in these two types of cysts. It was observed that fenestrated capillaries were found only in keratocysts. In addition, degeneration of endothelial lining associated with thrombosis was also a prominent feature of this cyst. While ruptured endothelium, narrow lumen and Weibel-Palade bodies were characteristic of vessels in dentigerous cyst. The presence of fenestrated capillaries in keratocyst and not in dentigerous cyst might indicate a rapid transfer of fluid to meet the demand of the relatively active proliferating epithelium, which may be promoted by growth factors released from platelets in those thrombosed vessels.

Degenerative changes in masseter and temporalis muscles in limited mouth opening and TMJ ankylosis.

The masseter and temporalis muscles were studied ultrastructurally in eight cases suffering from restricted mouth opening and TMJ ankylosis. The changes varied from slight degeneration of muscle fibers, such as accumulation of lipid or lipofuscin deposits, Z-band streaming and derangement of myofilaments, in one case to moderate or severe changes of muscle atrophy and necrosis in the remaining seven cases. Nemaline bodies were also observed in one of these seven cases. In addition to these muscle changes neural degeneration especially of myelinated nerves were found in three of the cases studied. The present findings showed that in spite of the diversity of the underlying factors affecting the joint, there was many similarities in the changes observed within the muscle. It is postulated that these degenerative muscle changes probably play an important role in restricted mouth opening and TMJ ankylosis, and that some of these muscle pathology may be the result of neural involvement.

Cementum-like material in a case of Pindborg tumor.

Pindborg tumor is characterized by the production of large amounts of amyloid and the presence of calcified lamellar bodies. These bodies were investigated at both the light and ultrastructural levels in a case of Pindborg tumor showing extensive calcification. It was found that the great majority represented calcified amyloid. However the outer layer or layers in some of these bodies consisted of typically banded calcified collagen which was referred to in this paper as (cementum-like material). This term was preferred over (bone-like material) because of the striking similarity between the arrangement of collagen in this layer and that of cemental Sharpy's fibers. It is therefore suggested that although the majority of the calcified lamellar bodies in this tumor represents calcified amyloid, cementum-like material may also contribute a part.

Further ultrastructural findings in epithelial cells of hairy leukoplakia.

Epstein-Barr virus and multivesicular structures appearing in lesions of hairy leukoplakia have been examined ultrastructurally in serial sections. It was found that both structures probably represent various levels of sectioning of transversely cut cell processes. The so-called viral nucleocapsid having a single membrane results when the plane of section is at right angles to one of the membranes but tangential to the other. While the so-called viral particle having two membranes would result if the plane of section is perpendicular to both the membranes of adjacent cells. The internal electron-dense core probably represents filaments enclosed within these processes and therefore does not represent DNA nucleotides. In addition, these nuclei contained bundles of filaments which probably represented tonofilaments. This was found to be due to tangential sectioning of the nuclear membrane surrounding deep cytoplasmic invaginations which led to the appearance of these filaments as if free within the nucleus.

Alteration in stereological density parameters of the mucosal vascular bed during neoplastic transformation in sublingual keratosis.

Stereological techniques have been used to study the vascularity in 110 sublingual keratosis lesions and 22 specimens of normal sublingual mucosa using an image analysis system "IBAS 1". The stereological parameters volume density (Vv), and surface density (Sv) were significantly increased in sublingual keratosis lesions as compared with those of normal sublingual mucosa. Lesions that eventually underwent malignant change showed the highest values and were highly significant (p less than .001) when compared with those which did not do so. The present results demonstrate that vascularity could be a supportive marker of impending malignant change in sublingual keratosis lesions.

Morphometric analysis of suprabasal cells in oral white lesions.

Surgical specimens from the cheek mucosa of 73 patients with white lesions were studied to determine various morphometric parameters that would help differentiate between the various types of oral mucosal white lesions that carry a risk of malignant change. Four cell types were represented: traumatic keratosis, leucoplakia, candidal leucoplakia and lichen planus, in addition to a control group of normal mucosa. The shape and size of the epithelial cells in two cell compartments, parabasal and spinous, were investigated by an interactive image analysis system (IBAS-1). The results showed an increase in the cell size in the parabasal cell compartment of all the white lesions compared with the normal mucosa. In the spinous cell compartment there was an increase in the cell size in lichen planus and traumatic keratosis; leucoplakia and candidal leucoplakia showed a slight decrease in cell size compared with the normal mucosa. Attempts to discriminate between the four groups of white lesions showed that these parameters can provide a high level of separation between lichen planus and the three other groups, but not between leucoplakia, candidal leucoplakia, and traumatic keratosis.

Crystalline inclusions in epithelial cells of hairy leukoplakia: a new ultrastructural finding.

Hairy leukoplakia is often the first manifestation of an HIV infection. In the present study we have investigated the ultrastructural features of hairy leukoplakia in two HIV seropositive male homosexual patients. Ultrastructurally EBV particles were found in the upper prickle and keratinized epithelial cells, whereas papilloma virus particles were not found. Candida albicans were also seen in the keratinized layer. In addition two types of inclusions which have not previously been reported in hairy leukoplakia were commonly seen in the epithelial cells containing the EBV. The first was a crystalline microtubular structure which may take the form of several arrays. The second was an elongated multivesicular structure consisting of membrane-bound rounded vesicles embedded in a background of fine filaments. The vesicles were similar to the empty looking EBV particles and their mean diameter was 100 nm. Further investigations are needed to elucidate the exact nature of these structures and their relationship to the Epstein-Barr virus.

Vascular degeneration in adenomatoid odontogenic tumour: an ultrastructural study.

The blood vessels in 3 cases of adenomatoid odontogenic tumour (AOT) were investigated ultrastructurally. An estimated 70-90% of the blood vessels found in the stroma showed degenerative changes which affected both the endothelial lining and the perivascular connective tissue. These vessels showed multiplication of basal lamina and were also encircled by concentric lamellae consisting either of collagen or fine filaments measuring 5-15 nm in diameter. Degradation of the layered collagen into fine filaments similar to those forming the concentric layers was observed. The present results suggest that the fine filaments of the concentric lamellae probably result from degradation of the layered collagen surrounding these vessels.

Melanin-forming Schwann cells in some oral mucosal lesions.

Normal oral mucosa and some mucosal lesions show melanin pigmentation, and it is usually assumed that melanin-containing cells in the lamina propria are melanophages. In a study of oral mucosa from two cases of lichen planus and tow of sublingual keratosis, many brown, intracellular, Masson-Fontana-positive granules were seen. At the ultrastructural level some of the melanin-containing cells displayed characteristics of Schwann cells rather than melanophages. These cells were surrounded by a basal lamina and contained unmyelinated axons. Although the majority of the melanin granules in these cells were compound melanosomes, single melanosomes and premelanosomes were also seen. These findings show that in sublingual keratosis and oral lichen planus lesions some of the melanin-containing cells in the connective tissue may be melanin-forming Schwann cells.

Morphometric analysis of basal cell layer in oral premalignant white lesions and squamous cell carcinoma.

The size and shape of the cells in the basal cell layer of the oral epithelium in 100 specimens from oral mucosa were studied by using an interactive image analysis system (IBAS-1). Four groups of white lesions (traumatic keratosis, lichen planus, leucoplakia, and a "risk group") in addition to two control groups (normal mucosa and squamous cell carcinoma) were studied retrospectively. The results showed a progressive increase in the dimensions (area, perimeter, and maximum diameter) of the nuclei from normal mucosa through traumatic keratosis, lichen planus, leucoplakia and the "risk group" to carcinoma, with considerable differences. The nucleus in squamous cell carcinoma was twice as large as in normal mucosa. A substantial increase in the dimensions of both the cell and the nucleus was found in the "risk group." The nucleo:cytoplasmic ratio, contrary to what might have been anticipated in risk lesions, did not show considerable differences between the diagnostic groups. Furthermore, it was slightly decreased in the risk group compared with the normal mucosa. The shape factors (form PE and contour index) seemed to be less helpful in the identification of the "risk group." The size of the basal cell and its nucleus can be of diagnostic value for lesions with a high risk of malignant transformation.

Mast cells containing melanin granules in sublingual keratosis.

In an ultrastructural study of 3 biopsies taken from the floor of the mouth of 2 patients suffering from sublingual keratosis, it was found that some of the mast cells appearing within the epithelium and connective tissue contained melanin granules which were found to be positive with Masson Fontana stain for melanin. These cells showed all the characteristic features of mast cells and not macrophages. The present results suggest that mast cells have phagocytosed melanin granules and therefore support those views suggesting that mast cells are capable of phagocytosis. They also suggest that not all the cells containing melanin granules and appearing in the lamina propria are the conventional melanophages but some of these may be mast cells.

Apoptotic bodies and abnormally dividing epithelial cells in squamous cell carcinoma.

Apoptotic bodies were investigated ultrastructurally in 10 cases of squamous cell carcinoma taken from buccal mucosa, tongue and larynx. Epithelial cells undergoing mitosis were found to show premature formation of nuclear membranes around various aggregates of chromosomal material giving the appearance of micronuclei. These cells were also shown to exhibit changes in their cytoplasm different from those seen in normally dividing epithelial cells. The changes seen in both the nuclei and cytoplasm of these cells were similar to those observed in cells undergoing apoptosis. It is suggested from this study that some apoptotic bodies, especially those of epithelial cell origin, may result from degeneration affecting cells in abnormal mitosis.

An ultrastructural study of binucleate plasma cells.

Fifty surgical specimens from 10 different diseases were examined for the presence of binucleate plasma cells. Thirty-three specimens showed binucleated plasma cells. Morphologically, they resembled mononuclear cells and contained abundant basophilic cytoplasm which ultra-structurally showed extensive rough endoplasmic reticulum. Their 2 nuclei exhibited the "cart-wheel" arrangement of heterochromatin characteristic of plasma cells. When serially examined the 2 nuclei remained separate. In addition, pairs of closely apposed plasma cells were observed. Some of these cells showed distinct apposing membranes separated by a gap of approximately 15 nm. While others, exhibited localised areas of indistinct membranes. There were also pairs of closely apposed plasma cells showing cytoplasmic bridges. These results suggest that the mode of formation of binucleate plasma cells is probably cell fusion. They also show that these binucleate cells are not confined to a single disease as they were found in 10 different diseases.

Amianthoid fibres in muscle tissue associated with temporomandibular joint ankylosis.

The masseter and temporalis muscles were studied ultrastructurally in 3 patients having extra and intra-articular ankylosis of the TMJ. Amianthoid fibres (thick collagen fibres) varying from 280-430 nm in diameter were found in the connective tissue of both muscles. These fibres appeared to form by fusion of collagen fibrils of normal thickness rather than representing an active dynamic process. The presence of amianthoid fibres in these muscles may account for the restricted mouth opening associated with TMJ ankylosis and could be of some value in future management of this condition.

Ultrastructural findings of muscle degeneration in oral submucous fibrosis.

Muscle changes were investigated ultrastructurally in 2 groups of patients having oral submucous fibrosis. One group was from patients with no evidence of restricted mouth opening and the other was from patients with restricted mouth opening. Electronmicroscopically, the majority of muscle fibres taken from the first group appeared normal with only occasional muscle fibres showing accumulation of homogeneous material and compression of the sarcomeres closest to this material. In contrast, the tissues from patients with restricted mouth opening showed severe changes and necrosis in a high proportion of muscle fibres. The necrotic muscle fibres exhibited complete loss of their plasma membrane, but in which the outline was maintained by an intact basal lamina. It is suggested from this study that restricted mouth opening in submucous fibrosis might depend not only on the subepithelial fibrosis but also on the extent of muscle degeneration.