| ameloblastoma | <oncology, tumour> A malignant jaw tumour (adamantinoma) which stems from the ameloblasts, cells which form tooth enamel. (09 Oct 1997) |
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| pigmented ameloblastoma | A benign neoplasm of neuroectodermal origin that most often involves the anterior maxilla of infants in the first year of life. It presents clinically as a rapidly growing blue-black lesion producing a destructive radiolucency; histologically, it is characterised by small round undifferentiated tumour cells interspersed with larger polyhedral melanin-producing cells arranged in an alveolar configuration. Synonym: melanoameloblastoma, pigmented ameloblastoma, pigmented epulis, progonoma of jaw, retinal anlage tumour. (05 Mar 2000) |
| pituitary ameloblastoma | <oncology, tumour> A form of primary brain tumour which develops in the pituitary gland. These tumours often secrete increased quantities of pituitary hormones (for example growth hormone) which can result in conditions such as gigantism and acromegaly. They are often benign and rare and comprise less than 5% of childhood brain tumours. Other symptoms include vision changes, headache and weight gain. Treatment often includes a combination of surgery and radiation therapy. (27 Sep 1997) |
| basal cell | <pathology> General term for relatively undifferentiated cells in an epithelial sheet that give rise to more specialised cells act as stem cells). In the stratified squamous epithelium of mammalian skin the basal cells of the epidermis (stratum basale) give rise by an unequal division to another basal cell and to cells that progress through the spinous, granular and horny layers, becoming progressively more keratinised, the outermost being shed as squames. In olfactory mucosa the basal cells give rise to olfactory and sustentacular cells. In the epithelium of epididymis their function is unclear, but they probably serve as stem cells. (13 Nov 1997) |
| basal cell adenoma | <tumour> A benign tumour of major or minor salivary glands or other organs composed of small cells showing peripheral palisading. (05 Mar 2000) |
| basal cell carcinoma | <oncology, tumour> The most common form of skin cancer. A malignant growth of epidermal tissue, specifically basal cells. most common in the fair-skinned on sun-exposed areas (especially the face). (15 Nov 1997) |
| basal cell epithelioma | <oncology, tumour> The most common form of skin cancer. A malignant growth of epidermal tissue, specifically basal cells. most common in the fair-skinned on sun-exposed areas (especially the face). (15 Nov 1997) |
| basal cell hyperplasia | Increase in the number of cells in an epithelium resembling the basal cells. (05 Mar 2000) |
| basal cell layer | The deepest layer of the epidermis, composed of dividing stem cells and anchoring cells. Synonym: basal cell layer, columnar layer, germinative layer, palisade layer, stratum basale, stratum cylindricum, stratum germinativum. (05 Mar 2000) |
| basal cell nevus | A hereditary disease noted in infancy or adolescence, characterised by lesions of the eyelids, nose, cheeks, neck, and axillae, appearing as uneroded flesh-coloured papules, some becoming pedunculated, and histologically indistinguishable from basal cell epithelioma; also noted are punctate keratotic lesions of the palms and soles; the lesions usually remain benign, but in some cases ulceration and invasion occur and are evidence of malignant change; autosomal dominant inheritance. (05 Mar 2000) |
| basal cell nevus syndrome | <syndrome> An inherited group of defects which involve abnormalities of the skin, eyes, nervous system, endocrine, glands and bones. The condition is characterised by an unusual facial appearance and a predisposition for skin cancer. (27 Sep 1997) |
| basal cell papilloma | A benign skin lesion resulting from excessive growth of the top layer of skin cells. It usually is found in persons over 30 years old and may be few or numerous. (12 Dec 1998) |
| basal squamous cell carcinoma | <tumour> A carcinoma of the skin which in structure and behaviour is considered transitional between basal cell and squamous cell carcinoma The term should not be used for the much more common keratotic variety of basal cell carcinoma, in which the tumour cells are of basal type but which contains small foci of abrupt keratinization. Synonym: basal squamous cell carcinoma. (05 Mar 2000) |
| carcinoma, basal cell | A malignant skin neoplasm that seldom metastasizes but has potentialities for local invasion and destruction. Clinically it is divided into types: nodular, cicatricial, morphaic, and erythematoid (pagetoid). More than 95% of these carcinomas occur in patients over 40. They develop on hair-bearing skin, most commonly on sun-exposed areas. Approximately 85% are found on the head and neck area and the remaining 15% on the trunk and limbs. (12 Dec 1998) |
| neoplasms, basal cell | Neoplasms composed of cells from the deepest layer of the epidermis. The concept does not refer to neoplasms located in the stratum basale. (12 Dec 1998) |