Anal malignant proliferative trichilemmoma: report of a rare case with review of literature.

Trichilemmoma is a rare type of benign cutaneous neoplasm, which derives from outer sheath of hair follicle. It barely develops malignant progression and has rarely been reported in anal cancer. In this article, we report a case of a 73-year-old woman who presented to the outer-patient department with complaints of a ruptured and longstanding anal phyma. All the appearances were atypical. Blood routine examination showed that neutrophilic granulocyte percentage was elevated and suggest it was a simple inflammation response. No evidence of malignancy was detected upon the laboratory examinations. Then we performed an abscess incision drainage for the patient. A few days later, the biopsy pathological report suggested the specimen is a malignant proliferative trichilemmoma. We decided to perform a wide local excision instead of an extended radical operation in order to preserve anus. After the surgery, we chose not to give chemoradio-treatment for fear of side effects and complications. Careful follow-up indicates that peri-anal malignant proliferative trichilemmoma may have a good prognosis and our treatment is a good choice for the patients with this tumor. Because of the low occurrence rate of anal cancer, especially malignant trichilemmoma, any clinical manifestation and experience are valuable. On one hand, our case may help to take the consideration of the diagnosis of malignant trichilemmoma in case of longtime-suffered peri-anal mass, on the other hand it propose a different treatment method from other anal cancers for clinical doctors.