Diagnosis of fibromatosis colli by fine-needle aspiration.

Fibromatosis colli is a benign disorder presenting as a neck mass in neonates and older children. The differential diagnosis includes malignancies such as rhabdomyosarcoma. Neck masses in ten infants, discovered between the second and sixth week of age, were evaluated by fine-needle aspiration (FNA). The male to female ratio was 7:3. In 8 patients there was good obstetrical history. Six of the 8 patients had a difficult delivery, as indicated by breech presentation or the need for forceps. Diagnostic aspirations were performed between the second to ninth week of age. The major cytologic finding was benign spindle fibroblasts, usually arrayed in clusters. The cells possessed plump, ovoid nuclei. There were also multinucleated cells consistent with degenerating skeletal muscle fibers. Only one case demonstrated significant inflammation. FNA can provide a rapid and reliable diagnosis in fibromatosis colli. There is support for the idea that in this setting, the disorder is related to perinatal muscular trauma.