Fine needle aspiration cytology of pseudosarcomatous reactive proliferative lesions of soft tissue

To summarize the diagnostic features of fine needle aspiration cytology (FNAC) of pseudosarcomatous reactive proliferative lesions of soft tissue and to establish the criteria for differentiating these lesions from true sarcoma, thus allowing conservative management.

FNA of 17 cases (13 nodular fasciitis, 2 proliferative fasciitis, 2 proliferative myositis), from 1994 to 2001, were reviewed in correlation with the clinical course or results of biopsy.

The FNAC features of pseudosarcomatous reactive proliferative soft tissue lesions were characterized by a pleomorphic pattern of proliferative cells and the presence of ganglion cell-like cells. The proliferative cells varied widely from spindle shaped, with long cytoplasmic processes, to more plump cells, with round to oval nuclei. In spite of the large nuclei and prominent nucleoli in ganglion cell-like cells, the nuclei were cytologically benign, with thin and smooth nuclear membranes and fine chromatin. Clinically, all lesions appeared as small, superficially located, rapidly growing nodules with a short duration of symptoms. Ten cases of nodular fasciitis, one case of proliferative fasciitis and two cases of proliferative myositis had a spontaneous resolution in 1-12 weeks (mean, 4.7) following diagnosis by FNAC. All patients were well and devoid of any symptoms or signs of recurrence or metastasis in a follow-up period of 1-64 months after FNAC or biopsies.

It is possible to differentiate pseudosarcomatous reactive proliferative soft tissue lesions from true sarcoma based on cytologic criteria in FNAC together with clinical correlation. All such lesions diagnosed by FNAC should be managed nonsurgically first, with follow-up. If regression does not occur within four to eight weeks, surgery should be performed.