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Fig. 1.72 Ameloblastoma. A An intact respiratory surface is subtended by a complex ameloblastic neoplasm with many lobules displaying a central stellate retic-ulum surrounded by the palisaded columnar ameloblastic epithelium. B Reverse polarity of the hyperchromatic columnar nuclei away from the basement membrane and towards the stellate reticulum. C Granular cell ameloblastoma showing islands of granular cells.

■îi1 h1 - - ' v ' ;r ■ • L'4 K î ■, 1 ■ : SJ v" ■

Fig. 1.73 Nasal chondromesenchymal hamartoma. A Loose spindle cell proliferation with a myxoid background. R The interface between the immature chondroid tissue and stroma resembles a chondromyxoid fibroma.

sues, some with identifiable foci of cartilage reflect the piecemeal nature of the resection in most cases. The precise site of origin of the mass has varied from the nasal septum, upper nasal cavity or floor of the anterior cranial fossa.

Histopathology

All tumours have had nodules of cartilage varying in size, contour and degree of differentiation. Some nodules resemble the chondromyxomatous nodules of a chondromyxoid fibroma, whereas others are well-differentiated cartilaginous nodules. At the periphery of the chon-droid nodules, there is a loose spindle cell stroma or an abrupt transition to hypocellular fibrous stroma. Other areas can have a fibro-osseous appearance with a prominent cellular stromal component and small ossicles or trabeculae of immature woven bone resembling fibrous dysplasia. Yet another common pattern is a cellular stroma with hyalin-ized nodules with or without perivascular stromal cells displaying a pericytoma-tous pattern. Cellular myxoid foci are similar in some respects to cranial/nodular fasciitis. The aneurysmal bone cystlike areas are surrounded by a stroma rich in multinucleated giant cells.

Immunoprofile

The cartilage, mature or immature, is immunoreactive for S-100 protein. The spindled stroma is immunoreactive for smooth muscle actin and vimentin.

Differential diagnosis

The differential diagnosis depends on the particular combination of microscopic features present in the biopsy or resection. Since cartilage is the dominant component, differential diagnoses include chondromyxoid fibroma and chondroblastoma {1858}. Other differential diagnoses may include aneurysmal bone cyst, fibrous dysplasia, cranial fasciitis and osteochondromyxoma {334}. Interestingly, the latter tumour may be congenital, may involve the paranasal sinuses and is associated with the Carney complex in some cases. None of the patients with nasal chondromes-enchymal hamartoma are known to have the Carney complex {1678}.

Prognosis and predictive factors

Information on the clinical behaviour is incomplete, but prognosis is apparently favourable. There is some capacity for continued local growth when the resection is incomplete.

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