Abstract

In biology, physiological ossification follows two well-studied mechanisms: intramembranous ossification, in which mesenchymal cells differentiate into osteoblasts, and endochondral ossification, where mineralization is preceded by cartilage formation. Most pathological ossifications, be it primary or secondary, apparently follow membranous ossification. Pathological ossification is a complicated process causing the formation of bone in soft tissues, such as muscle, skin, ligaments, and tendons. A variety of cells have the potential to undergo osteogenic differentiation in response to specific stimuli. Cutaneous ossification is an event that can be classified as primary or secondary to either inflammatory or neoplastic processes. It is referred to as primary when it occurs without a demonstrable preexisting lesion. Bone formation in pilomatrixoma, basal cell carcinoma, acne vulgaris, and melanocytic nevi are examples of secondary ossification. Pilomatricoma is a benign skin tumor that arises from hair follicle matrix cells. The histological components of pilomatrixoma are matrix cells and shadow cells. The shadow cells represent anucleate dead matrical cells destined to form hair shafts under physiological conditions. Ossification is not uncommon in pilomatricoma, which occurs over the shadow cells. An exciting finding is an antecedent or simultaneous carving of the shadow cell mass into trabeculae over which the bone is laid down. While this process's clear biologic directives and mechanisms are yet to be understood, this appears to be the only other example of ossification using a scaffolding besides endochondral ossification. It seems worth studying this process for its utilization in repair and artificial ossification.

Financial Disclosure:
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