Fine needle aspiration biopsy of fibromatoses

Fibromatoses form a spectrum of clinicopathologic entities characterized by the infiltrative proliferation of fibroblasts that lack malignant cytologic features. Fibromatoses present as nodular soft tissue masses almost anywhere in the body and thus are often amenable to fine needle aspiration (FNA). This report describes the FNA cytologic findings of fibromatosis in six patients ranging in age from 7 1/2 weeks to 36 years. Two of the lesions arose in the abdominal wall (musculoaponeurotic fibromatosis or extra-abdominal desmoid), and one each involved the plantar surface (Ledderhose's disease), the shoulder and the sternocleidomastoid muscle (Fibromatosis coli). The FNA of the shoulder was initially interpreted as nodular fasciitis due to the clinical presentation of a rapidly growing mass; an aspirate from the deep musculoaponeurotic region was believed to reveal a low grade sarcoma. The FNA diagnosis of musculoaponeurotic fibromatosis in a patient with familial polyposis coli suggested the diagnosis of Gardner's syndrome. Cytologically the aspirates consisted of groups of loosely cohesive, bland-appearing, spindle-shaped cells having oval to elongated nuclei and cytoplasmic tags. Individual spindle cells and rare inflammatory cells were also present. The aspirate of fibromatosis coli also contained degenerating skeletal muscle cells. Tissue confirmation was obtained in four cases. We believe that FNA is a useful procedure for the initial and recurrent diagnosis of fibromatoses and in the separation of fibromatoses from other benign and malignant soft tissue lesions. A discussion of other entities that enter into the cytologic differential diagnosis, such as mesenchymal repair, fasciitis and spindle cell types of sarcoma, is presented. From our experience we believe that the clinicopathologic features can suggest the diagnosis of fibromatosis, but histologic confirmation is recommended.