My dog has a hairless growth on her lip behind her whiskers. The veterinarian says it is a "young dog tumor" and doesn't recommend removing it. I am concerned because it is growing at a rate of about two centimeters a week. It seems to irritate her, as she scratches it often and it is frequently bloody. I can't find anything on the Internet about this type of growth. Could you tell me more about this condition?
Cutaneous histiocytomas are commonly referred to as button tumors because of their distinctive red, raised or dome-shaped appearance. Typically they are shiny and hairless and frequently ulcerate. Cutaneous histiocytomas appear on the face, eyelids, and head (especially the ears), and on the front legs and feet. They commonly affect dogs and arise at any age, but most commonly occur in dogs up to three years old. Certain breeds are more likely to develop these tumors, including Boxers, dachshunds, cocker spaniels, bull terriers, Great Danes and shelties. Purebred dogs tend to develop these tumors more frequently than mixed breeds. Single lesions are most common, but clusters or groups may also occur. The cause is unknown.
Cutaneous histiocytomas tend to grow rapidly and subsequently regress. Regression typically occurs over several weeks to a few months. Microscopic tissue studies have shown that that a characteristic lymphoid inflammatory infiltrate into the tumor occurs with regression of the mass. Apoptosis may play a role in tumor regression. Apoptosis is a process in which a cell altered by a tumor-forming or other disruptive process will self-destruct. As a result, many cutaneous histiocytomas resolve without treatment. (Many tumors will have begun regressing by the time the client wishes to investigate or to take action.) However, the tendency for these tumors to ulcerate, drain and scab, and cause secondary problems like infection justifies removing them surgically. Removal is by excision; superficial lesions may be frozen off with cryosurgery. Histiocytomas recur only infrequently after surgery or spontaneous regression.
Cutaneous histiocytosis is a somewhat related, although clinically distinct, condition that a veterinarian will rule out before either treating histiocytoma or choosing to monitor its regressing course. This condition, also called histiocytic proliferative dermatitis, consists of multiple benign, nodular tumors both in and beneath the skin. These tumors may appear on a wider range of an affected dog's skin than histiocytoma; they commonly arise on the nasal plane, scrotum, and back, as well as the eyelids. These tumors occasionally regress without treatment, but recurrence frequently occurs. Corticosteroids and certain other drugs may induce regression of these tumors. Cutaneous histiocytosis occurs most frequently in golden retrievers and certain other breeds.
Definitive diagnosis of either condition requires microscopic study of a sample of the tumor. Cytoanalysis of a fine-needle aspirate of the tumor can verify the tumor's histiocytic population of cells, although the lymphoid infiltrate can cloud the cellular diagnosis. In some cases the fine-needle aspirate sampling does not afford a clear cellular diagnosis. When this occurs, or if the studied tumor sample does not have a classic appearance, or when the lesions persist or if the affected dog patient is of a breed predisposed to cutaneous histiocytosis, I will recommend surgical resection of the tumors and histopathologic study. Some of these masses can be removed with a biopsy punch under local anesthetic (if the patient is amenable). The tissue should be submitted to a veterinary pathologist with a complete history for study and pathological (cellular/tissue) diagnosis.
Some malignant round cell tumors, such as mast cell tumors or solitary cutaneous lymphoma, can mimic the appearance of cutaneous histiocytoma. For this reason, some oncologists recommend removal of benign histiocytic tumors since it is not always easy to distinguish them from malignant tumors.
Please speak with your veterinarian about your concerns.
11/02/00
