Congenital reactive myofibroblastic tumor of the petrous bone: case report

Myofibroblastic tumors are members of a diverse spectrum of neoplastic and quasineoplastic lesions that occur most commonly during childhood and typically involve soft tissues. We present a case of a congenital reactive myofibroblastic tumor of the petrous bone (i.e., cranial fasciitis) that was successfully treated with surgical excision.

A newborn girl with congenital right facial palsy and deafness was noted during imaging evaluation to have a large enhancing mass that was destroying the right petrous bone and extending into the posterior and middle cranial fossae.

After embolization, an open biopsy was performed, which revealed a moderately cellular, spindle cell neoplasm without mitosis or necrosis, with scattered lymphocytes, eosinophils, and multinucleated giant cells. The spindle cells demonstrated strong immunoreactivity for vimentin, muscle-specific actin, and alpha-smooth muscle actin, with prominent reticulin staining between individual cells. Staining for CD68, a histiocyte marker, was positive within the multinucleated giant cells and many of the spindle cells; CD34, S-100, and desmin staining was absent. On the basis of these findings, the lesion was classified as a reactive myofibroblastic tumor, consistent with a cranial variant of nodular fasciitis. Because of the large size and significant mass effect of the tumor, a resection was performed several days later, using a combined supra- and infratentorial approach. Dense adherence of the mass to the walls of the sigmoid sinus and the carotid artery precluded complete resection without sacrifice of these vessels, which was not performed because of the known potential of these tumors to remain stable or regress after extensive subtotal resection. The presumed residual tumor subsequently regressed, and the patient has exhibited no detectable residual disease in 2 years of follow-up monitoring.

Reactive myofibroblastic tumors of the calvarium are uncommon lesions that superficially resemble sarcomas. Recognition of this diagnostic entity is important, to avoid unnecessary treatment with intensive adjuvant therapy. Although the management of these tumors relies predominantly on surgical resection, surgical decision-making should take into account the fact that small areas of residual disease can regress spontaneously.