PMC4872925_01
The pre-operative image shows a diffuse swelling in the left pre-auricular region producing an impression of a parotid mass. Note the "tent sign" (arrow). The skin appears taut and stretched. On careful examination, a faint bluish tinge over the lesion could be seen
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A 10-year-old girl presented with a painless, slow-growing swelling on left pre-auricular region that was noticed for 2 years (Figure 1). A careful re-examination of pre-operative image revealed a subtle bluish tinge, which was not observed presumably because of the dark-skinned complexion, and the characteristic "tent sign"perceptible through the already-stretched and bosselated skin surface (Figure 1).
Histopathology shows two predominant cell population of pilomatricoma - the basophilic basaloid cells with scanty cytoplasm, prominent nuclei and indistinct borders, and the eosinophilic anucleated "ghost cells" with relatively distinct borders, and with a transitional zone in between. As the tumor ages, the basaloid cells undergo apoptosis and become "ghost cells". Hematoxylin-eosin x 400
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In a typical example, the basophilic basaloid cells with scanty cytoplasm and indistinct borders encase the anucleated cytoplasm-rich eosinophilic "ghost/shadow cells" (Figure 2) with areas of keratinization, giant-cells and dystrophic calcification in the matrix.