Fine Needle Aspiration Cytology of Intranodal Myofibroblastoma

BACKGROUND: Intranodal myofibroblastoma is a rare, primitive, mesenchymal neoplasm of the lymph nodes first described in 1989. It behaves in a benign fashion and has a great predilection for the inguinal region. CASE REPORT: A 56-year-old man was referred for fine needle aspiration cytology of an inguinal lymph node. Smears were moderately cellular, with a predominant population of single, small spindle cells with no atypia. Most neoplastic cells were distributed as dissociated, single cells, with few groups. The cells showed metachromatic stromal material with a fibrillary quality. Nuclei were elongated, with pointed ends and occasional twisted forms. A remarkable finding on Papanicolaou-stained smears was hemosiderin granules. After a cytologic report of low grade spindle cell tumor, the node was excised, and a histologic and immunohistochemical diagnosis of intranodal myofibroblastoma was established. CONCLUSION: Intranodal myofibroblastoma should always be considered when aspirating solitary inguinal lymph nodes. The presence of a low grade spindle cell pattern of variably dissociated cells with hemosiderin granules should lead to immunocytochemical studies. Muscle-specific actin expression in the absence of S-100 protein and vascular markers permits a more specific diagnosis.