A. Fayyazi et al., CELL RENEWAL, CELL-DIFFERENTIATION AND PROGRAMMED CELL-DEATH (APOPTOSIS) IN PILOMATRIXOMA, British journal of dermatology, 137(5), 1997, pp. 714-720
Pilomatrixoma is a benign tumour of the cutaneous adnexa. Histological
ly, pilomatrixoma comprises masses of immature basophilic cells, small
numbers of polygonal squamoid cells, few transitional cells. and clus
ters of 'shadow cells'. The mechanism leading to the formation of shad
ow cells is still unknown. Skin biopsy specimens of pilomatrixoma (n =
15) were studied histologically, immunohistologically, and by applyin
g the in situ end-labelling technique, The basal layer of the basophil
ic cells included most of the proliferating cells with high expression
of bcl-2, and cytokeratin 19, The overlying basophilic cells showed a
negligible mitotic activity, a high significant accumulation of p53 p
rotein, and a heterogeneous, but progressive loss of bcl-2 and cytoker
atin 19, They developed either into squamoid cells or into transitiona
l cells. The squamoid cells were characterized as differentiated cells
resembling mature keratinocytes of stratified mucosa, The transitiona
l cells could be shown to represent apoptotic cells proceeding to shad
ow cells. The data suggest that apoptosis is the main mechanism leadin
g to the development of the dead shadow cells and is most probably res
ponsible for the banal biological behaviour of pilomatrixoma. Apart fr
om that, pilomatrixoma represents a suitable biological model to study
apoptosis in humans.