Pilomatricoma
(Calcifying Epithelioma of Malherbe)
Epidemiology:
- Children and young
adults
Common sites:
- Head and neck
- Upper extremities
Gross features:
- Solitary or
multiple
- dermal nodule
- cystic or solid
Histologic features:
- matrix follicular
differentiation
- proliferation of
small basaloid cells at periphery
- small, round hyperchromatic nuclei
- brisk mitotic
activity
- cells become more eosinophilic with washed out nucleus as you look more
centrally
- “ghost cells”
centrally / at cyst lumen
- dystrophic
calcifications in central portion
- metaplastic bone formation in old lesions
- foreign body
reaction to extravasated keratin
- May “ulcerate”
through epidermis
- Malignant pilomatricoma:
- Face
- Areas of infiltration,
mitoses, nuclear pleomorphism
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- Familial forms:
- AD inheritance
- Also associated with
Gardner’s syndrome
References: