Description, Causes and Risk Factors:
Multiple small benign nodules, occurring mostly on the skin of the face, derived from basal cells of hair follicles enclosing small keratin cysts; autosomal dominant inheritance.
Clinically, this disorder presents multiple, small, firm, often translucent, slightly coalescent tumors which show a decided predilection for the nasolabial folds, base of the nose, forehead, eyelids, about the ears, and only occasionally are they found on the scalp, neck and upper chest. The tumors are pin-head to pea-sized and usually are of normal skin color. They are often symmetrically distributed and show little or no tendency to ulcerate or to undergo malignant change. The lesions may remain stationary for a longer or shorter period of time, then suddenly increase in both size and number. Because of their translucency, these tumors may simulate vesicles or milia, and in the case of the individuals to be reported in this paper the eldest examined remarked that he could at times extract by pressure a “core of cheesy material” from several of the lesions.
The exact prevalence is unknown. Brooke's tumor appear to be rather uncommon. They most commonly appear in early childhood or at puberty. Both sexes are equally affected. There is no racial predisposition.
According to Cockayne the disorder is inherited as a dominant but with a definite though partial. The Journal of Investigative Dermatology limitation to the female sex, which is certainly rare in human heredity. This excess of affected females has been found to occur among the solitary cases as well as in the family groups. Sutton reported a remarkable incidence in a family of American negros in which every member (74 individuals, 28 males and 46 females) was affected; however, only the patient reported and the patient's three daughters and two sons were actually examined. In 1940 Goldman reported 10 cases in one family, in 7 of whom the diagnosis was verified by pathological study.
Genetic studies in families with Brooke's Tumor, two African American and one Caucasian, mapped the gene for Brooke's Tumor to chromosome 9p21 in the 4-cM region between IFN-alpha and D9S126. Several tumor suppressor genes have been mapped to this region, suggesting that the gene for Brooke's Tumor may be a tumor suppressor gene. It is also thought that Brooke's Tumor may be caused by more than two independent genes: one that occurs in isolation and is determined by a gene on 9p, and another due to impairment of the gene for cylindromatosis that maps to 16q12-q13 has been seen for the cause of tumors like cylindroma, trichoepithelioma, and spiradenoma.
Symptoms may include:
Small rounded and shiny tumors.
- Some time these tumors may be yellow, pink, brown or bluish.
- It is normally increase in number with age.
- Occurs in cheeks, eyelids and around the nose.
Diagnosis is based on history, clinical examination and it is confirmed by skin biopsy. If necessary, genetic studies may be used to detect the abnormalities in band 9p21. Horn cysts are characteristic histologic feature of Brooke's tumor. They consist of a fully keratinized inner shell surrounded by stands and solid nests of flattened basophilic cells resembling the cells of BCC (Basal cell carcinoma
). Adenoid structures may be present and calcification of cystic material and foreign body reaction to it may be seen. Occasionally, primitive hair papillae and even hair shaft-like structures may be observed, indicating a high degree of differentiation. A fibrous stroma surrounds the horny cysts. Histological differentiation from keratotic BCC may be difficult.
Treatment is difficult and often unrewarding. Preventive measures are unknown. Surgical excision and various destructive modalities including cryotherapy (the use of cold in the treatment of disease), dermabrasion (Operative procedure to efface acne scars or pits performed with sandpaper, rotating wire brushes, or other abrasive materials), electrodessication and curettage, have been tried with occasionally good results. Multiple treatments may be needed in several occasions. All methods carry significant risk for side effects, most importantly scarring. Recurrences are common. Recently, satisfactory clinical results have been reported with high energy pulsed CO2
laser, with no recurrences in treated area for 12 months. With the time, lesions of Brooke's tumor may become less obvious; therefore a wait-and-see strategy may be advisable.
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