Oral myofibromas: report of two cases and review of clinical and histopathologic differential diagnosis.

Myofibroma is a benign mesenchymal neoplasm composed of myofibroblasts which has been described with different synonyms since the first report in 1951. It may show clinical and histologic features that may be misinterpreted as a malignancy. We describe 2 cases of oral myofibromas affecting infants; the first one showed a rapid growth with teeth displacement and ulceration; the second one presented a relatively slow growth with an indolent course. Differential diagnosis included benign and malignant mesenchymal neoplasms, salivary gland tumors, and reactive processes. Microscopic analysis of both lesions revealed a spindle cell tumor with immunoreactivity for vimentin, muscle-specific actin, and specific smooth muscle isoform alpha-actin, rendering the diagnoses of myofibroma. The patients were treated with surgical excision, and both are in follow-up without any signs of recurrence. Myofibroma presents a wide range of differential diagnosis, including benign and malignant neoplasms. Therefore, accurate diagnosis may avoid an unnecessary aggressive therapy.

[Congenital myofibroma. A true hemangiopericytoma. A neonatal case with immunohistochemical and ultrastructural studies]. / Miofibroma congénito. Un hemangiopericitoma verdadero. Un caso neonatal con estudio inmunohistoquímico y ultraestructural.

We report the case of a male newborn infant with a pedunculated dermic tumor, located in the right malar region; who underwent a complete surgical resection of the tumor and had a satisfactory postoperative evolution. The histopathologic findings disclosed a subcutaneous tumor with a nodular aspect and a subendothelial intravascular growth, constituted by a dual population of small cells and spindle-shaped cells, distributed in a biphasic pattern. All tumor cells showed a strong pericellular reaction for PAS. The immunohistochemical studies revealed: diffuse cytoplasmic positivity for CD34 and Vimentin in all tumor cells, and only spindle-shaped tumor cells and less differentiated isolated neoplastic cells, presented cytoplasmic positivity for the smooth muscle alpha-actin. The electronic microscopy demonstrated a layer of basal membrane and in the citoplasm, numerous intermediate filaments with focal condensations. Based on all these findings, we conclude that this is a myofibroma, a "true hemangiopericytoma" with myofibroblastic differentiation. For this reason, we propose the term myofibropericytoma, in order to highlight its pericytic origin and its myofibroblastic differentiation. We emphasize the need to recognize this entity, in view of its low frequency and the possibility of a diagnostic mistake with other soft tissues tumors that display haemangiopericytoma-like features.