Spindle-cell rhabdomyosarcoma of the thumb: Rare site, rare tumor in a child

Spindle-cell rhabdomyosarcoma (RMS) is a relatively recently recognized favorable variant of embryonal RMS occurring mainly in the paratesticular and head and neck regions. Cytological reports of spindle-cell RMS have been sparse in the literature and the awareness of its cytological features is not very wide among cytopathologists. A 2-year-old girl was brought to clinical attention for a progressively enlarging swelling of right thumb. Imaging studies showed it to be a soft-tissue tumor in the subcutaneous region. Fine-needle aspiration yielded moderately cellular smears composed of small, round cells and few spindle cells with tapered cytoplasm. A cytological impression of RMS was rendered, which was later confirmed as spindle-cell RMS on excision biopsy. Spindle-cell RMS, a favorable prognostic variant of embryonal RMS, should be considered in the cytologic diagnosis of soft-tissue tumors with round cell and spindle cell morphology. This is especially true for tumors occurring in hitherto unreported sites. Diagn. Cytopathol. 2016;44:1094-1097. (c) 2016 Wiley Periodicals, Inc.