Pseudosarcomatous fasciitis and myositis: diagnosis by fine-needle aspiration cytology

Nodular fasciitis (NF), proliferative fasciitis (PF), and proliferative myositis (PM) are pseudosarcomatous lesions that typically resolve spontaneously. We previously reported the feasibility of diagnosing this family of lesions by fine-needle aspiration cytology (FNAC) based on 17 cases. The present study included 52 new cases (NF, 46; PF, 3; PM, 3) diagnosed by FNAC at Kiang Wu Hospital, Macau, 2001 to 2007, to validate the diagnostic features. All lesions appeared as recent-onset, small, superficially located, rapidly growing nodules. In 88% of cases (46/52: NF, 41; PF, 2; PM, 3), spontaneous resolution occurred in 1 to 16 weeks (median, 2 weeks) after FNAC diagnosis. FNAC smears were characterized by a hypercellular and polymorphic pattern of lesional cells and distinctive ganglion cell-like cells in most cases. Most cases of NF (36/46 [78%]) showed "typical" cytologic features. A minority of NF cases showed granuloma-like or myxoid features. FNAC is an effective diagnostic tool for NF, PF, and PM; a correct cytologic diagnosis spares patients an operative procedure. Excisional biopsy can be reserved for cases showing atypical clinical courses or in which FNAC shows low cellularity with absence of ganglion cell-like cells.