Congenital-infantile fibrosarcoma (CIFS) is a cellular, mitotically active neoplasm with a paradoxically limited biologic potential in most cases. Its phenotype and proliferative features have been incompletely explored with inconclusive results. We studied the clinical, pathologic, immunohistochemical, and flow cytometric features of 26 cases (16 males, 10 females; 92% of cases detected within the first year life; 11 on extremities, 10 on the trunk, 5 in the head and neck). All displayed interlacing fascicles of spindle cells with focal necrosis, mitoses, and a focal hemangiopericytomatous vascular pattern. Immunohistochemically, 22 of 22 cases were reactive for vimentin. Other markers were present in a minority of cases. Flow cytometry of formalin-fixed, paraffin-embedded tissue in 10 cases demonstrated moderate to high proliferation activity and diploid DNA content in nine cases. Follow-up of all 26 patients revealed 20 patients alive and well, 15 without evidence of recurrence, and 5 with a small residual mass. Six patients had died of tumor; none had distant metastases. Patients with tumors in the head and neck or deep truncal soft tissues, including mesentery, had a poor prognosis because of local extension. CIFS is a clinically and morphologically homogeneous condition with considerable immunophenotypic diversity. Diploid DNA content in the majority of cases suggests that it may not be a fully expressed sarcoma. The clinicopathologic features are sufficiently distinctive to permit recognition and warrant conservative initial treatment in most cases. "Fibrosarcoma" is a term of convenience rather than of nosologic certainty..
- Congenital-infantile fibrosarcoma