Cytologic features of primary, recurrent, and metastatic dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a low-grade spindle cell neoplasm involving both dermis and subcutis. Its diagnosis may be difficult to render from cytologic smears, as it shares some features with other spindle cell lesions occurring in the skin and soft tissue.

Fourteen aspiration smears from 12 patients with primary, recurrent, or metastatic DFSP, examined by fine-needle aspiration biopsy (FNAB), were reviewed and compared with corresponding surgical specimens (13 aspirates) and clinical data (one aspirate). The cytologic features of DFSP were evaluated. Other spindle cell lesions in the differential diagnoses were discussed.

Unequivocal spindle cell sarcoma diagnoses were rendered in nine aspirates, six of which were labeled correctly as DFSP in the original reports. In three aspirates, the preoperative diagnoses were inconclusive with regard to whether the tumors were benign or malignant. Two aspirates were diagnosed erroneously as benign spindle cell lesions. Cytologic features included tight clusters of bland spindle cells embedded in a collagenous/fibrillar and, often, metachromatic matrix along with dissociated, uniform, or slightly atypical spindle cells or bare nuclei. Tissue fragments showing a storiform pattern and entrapped fat tissue, reported in previous series, were less characteristic, presenting in nine and seven aspirates, respectively.

Correct subtyping of DFSP in fine-needle aspiration smears can be difficult, due to its morphologic overlapping with other spindle cell lesions. A combination of cytology with ancillary studies and appropriate clinical information is crucial to establishing a correct diagnosis.