Bcl-2 Immunoexpression in Rapidly Growing Eyebrow Pilomatrixoma after Blunt Trauma
Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is an uncommon benign cutaneous neoplasm that that arises from matrix cells of hair follicle. It typically presents as a superficial, firm, solitary, slow-growing, painless dermal or subcutaneous mass in the head and neck region, including the eyelid or eyebrow [1,2]. Rapidly growth pilomatrixoma is extremely rare and mostly reported following trauma [3,4]. Herein, we present one patient with rapidly growing eyebrow pilomatrixoma with strong Bcl-2 immunostaining following trauma, and try to explain the role of trauma in the development of pilomatrixoma by immunohistochemical analysis, which was not mentioned in the prior article.
A 17-year-old girl noticed one painless nodule over right eyebrow region with progressive enlargement for 1 week. She experienced blunt trauma to right upper eyelid before the mass appeared. On palpation, a firm and mobile nodule, 4×4 mm in size, was detected below the right eyebrow with surrounding ecchymosis. (Figure 1A). Excision biopsy was done and the histopathologic examination demonstrated an admixture basaloid hair matrix cells, and eosinophilic amorphous enucleated ghost cells, confirmed the diagnosis of pilomatrixoma. (Figure 1B and C). Immunostaining showed strong positivity for Bcl-2 in the peripheral basaloid cells of the lesion (Figure 1D). The patient remains free of tumor 3 years later.
The etiology of pilomatrixoma is not completely understood. While trauma has been postulated as a cause of bullous appearance of anetodermic variant of pilomatricoma . In a large case series of 40 cases of eyelid pilomatrixomas, 6 patients (15%) had a history of preceding trauma to the involved area . It has been proposed that trauma might rupture a vessel wall and cause hemorrhage into an existing lesion, producing enlargement of the tumor. Red-blue discoloration of the skin is a typical feature of pilomatrixoma and could help to differentiate it from inclusion and dermoid cysts which are often misdiagnosed
clinically . Dermoid cysts following trauma can leak their cystic substances into surrounding soft tissues, causing rapid growing of the lesion. However, the skin over dermoid cysts looks normal and can be moved freely over the lesions, which are different from pilomatrixoma.Bcl-2-positive immunostaining has been reported in the peripheral proliferating basaloid layers of pilomatrixoma [8,9]. Bcl-2 is a proto-oncogene that helps to suppress apoptosis in both benign and malignant tumors and has been supposed to contribute to the pathogenesis of pilomatrixoma by faulty suppression of apoptosis . However the relationship between trauma and expression of Bcl-2 protein in the pilomatrixoma has not been addressed. Bcl-2 immunostain was strong positive in current case of pilomatrixoma which developed rapidly after trauma. Human and animal studies have shown that Bcl-2 proteins are increased after traumatic insults [11,12]. It is possible that increased expression of Bcl-2 after trauma promotes cells proliferation by regulating apoptosis and contribute to the development of pilomatrixoma.
Whether the cause-effect relationship between trauma and pilomatrixoma remains to be established, however, trauma is probably important in producing enlargement of an existing pilomatrixoma.
11.Jeschke MG, Bolder U, Finnerty CC, Przkora R, Müller U et al. The effect of hepatocyte growth factor on gut mucosal apoptosis and proliferation, and cellular mediators after severe trauma. Surgery. 2005, 138: 482-489.