Sebaceous Carcinoma

I thought I would write a little about uncommon and interesting cancers that I have run across. Here is one I have seen just recently:

Sebaceous Carcinoma

First noted in 1891 this cancer is thought to arise from the sebaceous glands in the skin and can be found anywhere on the body where these glands are  found. It is commonly overlooked as a benign lesion which often delays treatment. A great majority of these tumors can be found in the periocular region, with just 25% of reported tumors occurring on the head and neck. In head and neck sebaceous carcinomas, the parotid gland represents 30% of cases. The clinical course of this carcinoma is aggressive in nature with significant local recurrence and metastatic disease. Site of distant mets are liver, lungs, bone and brain, and can occur as late as five years after initial diagnosis. Women develop this cancer more than men and it has greater frequency in the Asian population.
Sebaceous Carcinoma is associated with Muir-Torre syndrome, a rare autosomal dominant disease characterized by skin lesions, including benign and malignant sebaceous neoplasms, keratoacanthomas, and internal visceral malignancies (gastrointestinal and other sites).
This syndrome is a subtype of hereditary nonpolyposis colorectal cancer syndrome, occurring in approximately 5 out of every 200 patients. Approximately 60% will develope metastatic disease with a 50% survival rate calculated at 12 years. Lesions outside the head and neck have a more aggressive course. Cutaneous sebaceous neoplasms can precede or follow a diagnosis of visceral malignancy, although they usually develop later.
•Sebaceous carcinomas most commonly occur on the eyelids, where they generally arise from the meibomian glands and the glands of Zeiss. They may also occur almost anywhere on the skin, including the ears, the feet, the penis, and the labia. On the eyelids, the tumor appears as a firm, yellow nodule with a tendency to ulcerate. Clinically, these lesions are often mistaken for chalazia, chronic blepharoconjunctivitis, or carbuncles. Sebaceous carcinoma of the eyelid can invade the orbit and can frequently metastasize and cause death. Extraocular tumors can also metastasize but are less likely to cause death.

•The most common visceral neoplasm in MTS is colorectal cancer, occurring in almost one half of patients. The tumors are usually proximal to the splenic flexure. The second most common site is the genitourinary tract, representing approximately one quarter of visceral cancers. A wide variety of other cancers, including breast cancer, lymphoma and rarely leukemia, salivary gland tumors, lower and upper respiratory tract tumors, and chondrosarcoma, are reported. Intestinal polyps occur in at least one quarter of patients. Other benign tumors described in MTS include ovarian granulosa cell tumor, hepatic angioma, benign schwannoma of the small bowel, and uterine leiomyomas.

http://emedicine.medscape.com/article/1101433-overview