Pilomatricoma

Pilomatricoma, also known as calcifying epithelioma of Malherbe, is a benign skin tumor derived from hair follicle cells. First described by Malherbe and Chenantais in 1880, pilomatricoma is relatively uncommon and typically presents as a small, firm, solitary nodule located in the dermis or subcutaneous tissue. Although it can occur at any age, it is most commonly found in children and young adults. The tumor has a predilection for the head, neck, and upper extremities but can appear anywhere on the body.

Etiology and Pathogenesis

The exact cause of pilomatricoma remains unclear, but it is believed to originate from the matrix cells of the hair follicle, which are responsible for hair formation. Genetic factors may play a role in its development, as evidenced by its association with certain genetic conditions such as Gardner's syndrome and myotonic dystrophy. Mutations in the CTNNB1 gene, which encodes β-catenin, have been identified in many pilomatricomas, suggesting a role in tumorigenesis.

Clinical Features

Pilomatricoma typically presents as a solitary, painless, firm nodule that is deep-seated and may be attached to the overlying skin. The overlying skin can appear normal, bluish, or reddish in color. The size of the tumor usually ranges from 0.5 to 3 cm in diameter. While pilomatricomas are generally asymptomatic, they can become tender or painful if inflamed or infected.

Diagnosis

The diagnosis of pilomatricoma is primarily clinical, based on the characteristic appearance of the lesion. However, definitive diagnosis often requires histopathological examination. Imaging techniques such as ultrasound may be helpful in assessing the lesion's depth and characteristics but are not diagnostic. Histologically, pilomatricoma is characterized by the presence of ghost cells, basaloid cells, and calcification.

Treatment

Surgical excision is the treatment of choice for pilomatricoma, with the aim of complete removal to prevent recurrence. The procedure is typically performed under local anesthesia on an outpatient basis. Recurrence is rare but can occur, especially if the tumor is not completely excised.

Prognosis

The prognosis for pilomatricoma is excellent, as it is a benign tumor with no malignant potential. However, patients should be advised of the small risk of recurrence following incomplete excision.

Epidemiology

Pilomatricoma accounts for about 1% of all skin tumors. It has no racial predilection and shows a slight female predominance. Although it can occur at any age, it is most commonly diagnosed in children and adolescents.

Conclusion

Pilomatricoma is a benign skin tumor that arises from hair follicle cells. It is characterized by a firm, solitary nodule that is typically painless. Surgical excision is the definitive treatment, and the prognosis is excellent. Awareness of this condition is important for healthcare providers to ensure accurate diagnosis and management.

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Pilomatricoma

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  Histopathology of pilomatricoma, high magnification, annotated
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  Pilomatrixoma - high magnification