What is Pilomatricoma?
Pilomatricoma is a benign skin tumor involving the hair matrix. It is also known as Malherbe calcifying epithelioma or calcifying epithelioma of Malherbe. It was previously known as Pilomatrixoma before the term Pilomatricoma.
Pilomatricoma on the Cheeks
The histologic characteristics of pilomatricoma involve the appearance of ghost cells or anucleate squamous cell, multi-nucleated giant cells and benign viable squamous cells.
Pilomatricoma is harmless and does not progress to skin cancer. It is commonly present in children, but may also affect adults. The tumors arise on the head and neck where hair follicles are present, but it may develop in other parts of the body. The lesions are skin-colored, but may be purplish in other patients.
Epidemiology of Pilomatricoma
Pilomatricoma is responsible for twenty percent of tumors involving the hair matrix, and is the most common tumor affecting it. The incidence of pilomatricoma is up to 40% in children less than 10 years of age and 60% in people before the age on twenty.
Females are more at risk for developing it. It is also common among fair-skinned people or those belonging to the Caucasian race. More than 50% of cases has pilomatricoma tumors on the head and neck. Other areas of the body where pilomatricoma may develop are in the extremities and trunk.
History of Pilomatricoma
Pilomaticoma was first described in 1880 by Chenantia and Mahlherbe. They thought that the condition was caused by a problem on the sebaceous glands. Because of this, Pilomatricoma was named as Malherbe Calcifying Epithelioma. In 1922, Cezenave and Dubreuilh described the characteristic histologic finding of the tumor.
After that, it was Kraier and Turhan who associated the growth of pilomatricoma tumors with the hair matrix in 1942. The term Pilomatrixoma was used in 1961 because of its association with the hair matrix. However, it was changed to Pilomatricoma in 1977 because of being etymologically correct and as opposed to epihtelioma, which is more of malignant in nature.
Symptoms of Pilomatricoma
Symptoms of pilomatricoma include:
- Tumors are angulated in shape otherwise known as the “tent” sign
- Tumors feel bonny and rock hard because of the calcifications
- Tumors are slow growing
- Bluish to red or purplish skin lesions
- Usually occurs solitary
- Freely mobile tumors due to a well encapsulated structure
- May grow up to 5 cm in diameter
Pilomatricoma Showing Red, Angulated and Encapsulated Lesion
Pilomatricoma is sometimes mistaken for lipoma, dermoid cysts or sebaceous cysts.
Causes of Pilomatricoma
The exact cause of pilomatricoma is unknown, but several factors are associated with its occurrence. These include:
- Genetics– There is an association of pilomatricoma with the over activity of the BCL-2 gene, a proto-oncogene. There is also a mutation in the CTNNB1 gene, which results in the loss of protein complex regulation of beta catenin. With the over activity of the proto-oncogene, the normal process of cell death is inhibited, leading to overgrowth of the tumor.
- Other genetic diseases– The occurrence of pilomatricoma may also be observed in people with myotonic dystrophy as a result of genetic abnormalities. Conditions such as Turner’s syndrome, Rubinstein-Taybi syndrome, Steinert’s syndrome, Gardner’s syndrome and sarcoidosis may also cause the growth of pilomatricoma. However, much of the cases of pilomatricoma are not associated with other diseases.
Diagnosis of Pilomatricoma
Physical examination of the tumor as rock hard may give a suspicion of the occurrence of pilomatricoma. However, the diagnosis of pilomatricoma prior to surgery is sometimes difficult because of its resemblance to other tumors involving the hair matrix. Surgeons also do not consider other tests before the surgery or removal. However, diagnosis of pilomatricoma may be done using the following diagnostic examinations:
- Ultrasound– Ultrasound scan may be used to assess the tumor. The results may indicate a doughnut-like tumor with calcifications or tail.
- X-ray– X-ray imaging also is able to identify the characteristic of the tumor with calcifications
- Biopsy– Biopsy is the most common diagnostic tests for the development of tumors. This may indicate the characteristics of the tumor, its histological make-up and whether it is benign or malignant. Biopsy serves as a treatment and a diagnostic test. The surgeon may remove the entire tumor and subject it to histologic testing. Histologic tests may also reveal calcium deposits in the lesions with darkly stained cells and missing nuclei.
Treatment of Pilomatricoma
The primary treatment of pilomatricoma is the removal of the tumor. Surgical removal may employ the following procedure:
This procedure involves the surgical removal of the tumor by the use of surgical instruments such as scalpel and scissors. Excision of pilomatricoma is relatively easy because most of the tumors are encapsulated. However, recurrences may arise after the procedure when incomplete excision is performed. During excision, the presence of a less defined tumor that adheres to the surrounding tissues may indicate malignancy.
Complications of Pilomatricoma
Complications of pilomatricoma include the growth of the tumor to a large size up to few centimeters in diameter. Cancer resulting from pilomatricoma is rare. Pilomatrix carcinoma or cancer arising from pilomatricoma is characterized by hyperchromatic, rapidly proliferating and pleomorphic cells.
There is also tumor necrosis, atypical mitosis and asymmetry of the cells. Aside from a malignant complication that is rare, pilomatricoma may develop to progressive tumor, which is a benign tumor characterized by sharp circumscription and symmetry of the cells.
Prognosis of Pilomatricoma
Pilomatricoma seldom progress to malignancy. Recurrence of the condition is also rare when careful excision is performed. The presence of multiple recurrences should be evaluated with pilomatrical malignancy.
Severe form of Pilomatricoma
An Excised Pilomatricoma
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