Cementum is the bonelike, mineralised tissue covering the roots of vital teeth. It is a specialised connective tissue, similar to the osseous tissue, and the most important difference is cemental avascular structure. Cementoma develop from multipotent cells of the periodontal membrane, and by their multipotency those cells may produce connective tissue, cementum or bone. Pathological development of the periodontal membrane may thus result in the formation of tumours, composed of connective tissue, cementum and lamellar bone in different ratios (1).
Benign fibrous ossifying lesions are a problem in diagnostics and classification. The WHO classification from 1992 divides them into tumour lesions; cementifying fibroma and ossifying fibroma, and fibrous dysplasias, which are not tumours in the narrow sense. Numerous classifications aimed to classify tumours according to their clinical picture, aggressiveness and prognosis. The terms thus introduced, such as "juvenile active ossifying fibroma", "aggressive", "active", "psammomatoid", "juvenile active", are still rather controversial (2). Special clinical and diagnostic challenges are tumours located outside the jaws.
We report a case of a nine-year-old girl, referred to our hospital because of frontal headaches, impaired vision and pain in the right eye. Her family's medical history was unremarkable; the patient is sensitive to dermatophagoides and pollen. All laboratory test results and lung x-rays were negative. The status at admission to hospital revealed a ball-shaped mass in the medium nasal meatus, which was defined as a concha bullosa. There was no pathological secretion; other ENT exams were normal.
MR imaging showed a mucocele of the front and rear ethmoid, destroying the orbital wall and breaking into the orbit, retention and thickened mucous membrane of the right maxillary sinus (Figure 1). The patient underwent an internal ethmoidectomy on the right side and extirpation of the mucocele by functional endoscopic surgery. Nasal endoscopy showed a mucocele in the medium nasal meatus, which was protruding fairly in front of the front pole of the medium nasal conchae. The formation was punctured and clear liquid was aspirated from the same. The mucocele wall peeled off from the ethmoid roof, the medium nasal shell and the periorbit to which it adhered and which was pushed by the mucocele. The endoscopic examination revealed softened bone of the base of the skull in the region of the posterior ethmoid. The natural orifice of the maxillary sinus dilated, in which thickened mucous membrane and some retention secretion were found. Endoscopies were repeated several times, without major mutilation consequences and without consequences for vision and nasal passages (Figure 2).
It is possible to state that there are no uniform pathomorphological criteria for differentiation between cemento-ossifying dysplasias and cemento-ossifying fibroma. Histologically, fibromas are most often characterised by equal parts of calcified tissue and fibrous tissue; however, the ratio between these two tissues can vary, depending on the fibroma subtype. Calcified structures show a grid-like or an isolated lamellar structure with predominant osteoblasts and a few osteoclasts. Round or lobulated bone density mass may be more or less incorporated into the tumour, and their prevalence shows an image of a "cementifying fibroma". The presence of mineralised ossicles, "psammoma", is mentioned in recent literature. These are mineralised oval ossicles, not rimmed with osteoblasts. Connective tissue is composed of layers of spindle fibroblastic or stellate cells with focal areas of storiform patterns. Such microscopic composition is also directly responsible for major macropathological and clinical features of tumours, particularly in contrast to related dysplasias, and these are radiolucency, encapsulation, and slow and non-infiltrative growth (3, 4).
Most often, cementifying fibromas occur periapically in the maxilla and mandible; which is logical in view of its origin from the periodontal ligament. There are three clinical stages in their growth. The first stage destroys the bone, the tumour is without infiltrations of bone and cementum; in the second stage there are infiltrations of bone and cementum, and the tumour becomes opacifying luminiscent. When it reaches the third stage, the tumour stops to grow. It is marked by a well-demarcated, radiographically hyperlucent lesion and bone lesions. An average tumour diameter after the end of its growth is 3.8 cm (5).
Cementoma with sites outside the maxilla and mandible are quite different because they remain in an immature, active stage, which results in destructive growth and frequent relapses. The first case was described by Krausen et al. in 1977 (6). Tumour development outside the jaws is explained with ectopic cells of the periodontal membrane originating from the primitive mesenchymal ridge, which can appear there from embryologically underdeveloped tissue, after a surgery or after infection (7-9). Predominance of psammomatoid cells is found in approximately 11% of all cementifying osteofibroma. However, the frequency of cells increases with the distance between the site and the jaws. Thus psammoid cells would presuppose more aggressive behaviour of tumours with untypical sites: ethmoid and frontal sinuses, bones and soft tissues of the head (9).
Until the mid-1990s, the occurrence of cemento-ossifying fibromas outside the jaws was considered a rarity. However, in recent times, several cases are reported each year. The case reported above is extremely rare due to a cystic shape of the lesion itself. Fujimoto et al. reported first on such a case. Upon biochemical analysis of the aspirate they attempted to explain the cystic shape of the lesion with a rupture of the blood vessel and consequential compression necrosis of the tumour itself (10). Although aggressive, prone to relapses and penetration into surrounding vital structures of the face, cementifying fibromas outside the area of the jaws have a good prognosis, without mutilating consequences. Resection is the therapy of choice. Malignant alteration is possible, however, rarely (1, 4, 7, 10).