Malignant pilomatricoma: an immunohistochemical study with antihair keratin antibody

Pilomatricoma is generally benign. This tumor develops in the cells of the hair matrix, and the tumor cells themselves tend to differentiate into a form resembling hair cortical cells. However, it is possible for a pilomatricoma to become cancerous; only 29 instances of this uncommon event have been reported in the medical journals. The authors report the case of an 88-year-old woman who died of complications of cancer and its treatment; only after her death was the cancer found to be malignant pilomatricoma. The patient was seen originally because of gradually progressing edema, the accumulation of fluid in the tissues of her right leg. Numerous hard nodules, between 1 and 2 centimeters, were found in the patient's right inguinal region upon physical examination. Similar nodules were not found in other regions, including the abdomen and rectum. A biopsy was performed, and microscopic evaluation of the specimen suggested that the nodule was a lymph node contaminated with cancerous cells from a squamous cell carcinoma. A primary squamous cell carcinoma which could account for these nodules was not found, but the patient was treated with chemotherapy and radiation therapy. Two years after treatment, the patient died of kidney failure. At the time of her death, metastatic cancer could be identified in the skin of her abdomen and in the tissues behind the peritoneal cavity. At autopsy, specimens were obtained for further study. Microscopic specimens were stained using antibodies specific for hair keratin. (The staining properties of this antibody are different from those of other forms of keratin such as epidermal skin keratin.) This hair antibody was found to stain normal hair matrix and the patient's tumor cells; the antibody did not stain components of normal skin, indicating that the tumor was biochemically similar to the hair matrix and was therefore a pilomatricoma. (Consumer Summary produced by Reliance Medical Information, Inc.)