Pilomatrix carcinoma

What is pilomatrix carcinoma?

Pilomatrix carcinoma is a rare malignant hair follicle tumor that arises in a benign pilomatricoma. It was not until 1980 when a review of several cases of biologically aggressive pilomatricoma confirmed the malignant transformation of these normally benign tumours. Since then there have only been about 90 reported cases of pilomatrix carcinoma. Some of these cases of pilomatrix carcinoma have arisen as a solitary lesion de novo. There is a high risk of recurrence after surgical excision and malignant features are often found in recurrent lesions.

Other names for pilomatrix carcinoma include pilomatricarcinoma and pilomatrical carcinoma.

What are the clinical features of pilomatrix carcinoma?

Lesions of pilomatrix carcinoma are often found on the head and neck regions and vary in size from 1-10 cm. Unlike their benign counterpart where lesions are most often diagnosed in young children of both sex, the malignant variety is twice as likely to appear in white middle-aged men.

Lung metastases has been described and may occur years after the initial diagnosis.

How is pilomatrix carcinoma diagnosed?

The diagnosis of pilomatrix carcinoma is based on histological examination of a skin biopsy specimen. Although pilomatrix carcinoma share some histological features with benign pilomatricoma, the following additional features are clues to the malignant diagnosis:

• Frequent and abnormal mitosis
• Central or intratumoral necrosis
• Infiltration of skin and soft tissue
• Infiltration of blood and lymphatic system

A MRI scan (magnetic resonance imaging) of the lesion may be required to determine the local spread of the tumour. Palpation of lymph nodes and a CT scan may also be performed to search for lung and liver metastases.

What is the treatment of pilomatrix carcinoma?

Due to the potential for metastasis to various sites, complete surgical excision with wide margins (2-3cm) is the recommended treatment. Mohs micrographic surgery may be used to ensure better margin control. Incomplete resections have led to local recurrences.

Adjuvant radiotherapy also has been used, but potential benefits are not well defined.