MITOTIC PHASE DISTRIBUTION, MITOTIC-ACTIVITY AND APOPTOSIS IN BASAL-CELL TUMORS OF CANINE SKIN

This study evaluates the mitotic phase distribution, mitotic activity and apoptosis in 17 basal cell rumours of canine skin. The number of m itotic and apoptotic cell/mm(2) of neoplastic epithelium is counted an d the volume corrected mitotic and apoptotic index, respectively, are obtained (M/V and A/V index). Transmission electron microscopy is perf ormed on selected cases to confirm the typical features of apoptosis. The M/V index ranges from 9 to 45/mm(2) of neoplastic epithelium, whil e the A/V index ranges from 5 to 111/mm(2) of neoplastic epithelium. E ven if the number of apoptotic cells is slightly higher than that of m itotic cells and vice versa, the mean values of the two parameters (me an M/V = 20.76 +/- 10.86, mean A/V = 31.41 +/- 24.53) tend to be equal . In fact, apoptotic and mitotic index are not statistically different (P = 0.11). Furthermore, in all the samples examined, an increased pr oportion of metaphases (46.82%) is observed. These findings suggest th at the discrepancy between apparent mitotic activity and tumour growth may be mainly due to the increased duration of the entire cell cycle rather than to the high incidence of apoptosis.