Congenital myofibroblastic tumor (CPMT) is a rare tumor found in utero and newborns. While its histology suggests a sarcoma (previously referred to as a fibrosarcoma or leiomyosarcoma) its behavior is benign.
Presentation:
(1) nonimmune hydrops fetalis
(2) lung mass on chest X-ray
(3) neonatal respiratory distress
(4) intrauterine fetal demise
Pathologic findings:
(1) gross appearance: white or pink solid and cystic mass
(2) proliferation of spindle or round cells
(3) spindle cells show primarily a fascicular pattern of growth
(3) variable presence of cartilage
(4) variable hemangiopericytoma-like vascular pattern
Features confused with malignancy:
(1) high mitotic rate
(2) tumor necrosis
(3) infiltrative growth
Features indicative of benign behavior:
(1) absence of recurrence even with positive surgical margins
(2) absence of metastases
Immunohistochemical features of myofibroblastic differentiation:
(1) vimentin positive in both spindle and round cells
(2) smooth muscle actin positive in spindle cells
The cells are negative for desmin, cytokeratin, EMA and Factor VIII.
