Case Of The Month -February 2006

Rhabdomyosarcoma

Contents

• Clinical Details
• Cytological Findings
• Histology
• Immunohistochemistry
• Discussion
• References

Clinical Details

18-Year-old male patient with an initial presentation of a left submandibular lump. The clinician suspected a Pleomorphic Adenoma and a FNA biopsy was taken and send to us for analysis. No other relevant history was indicated.

Cytological Findings

The aspirate is highly cellular, and the features are those of a high-grade malignancy. Numerous individually dispersed tumour cells, as well as densely packed aggregates of "spindle" looking cells are present. There is a marked degree of nuclear pleomorphism, with a high nuclear cytoplasmic ratio and numerous multinucleated giant tumour cells. The features are those of a small round cell tumour of childhood and, considering the site and heterogeneity, a rhabdomyosarcoma was diagnosed and an excision biopsy recommended to confirm the tumour type.

Cyto Image 1 of 4

Cyto Image 2 of 4

Cyto Image 3 of 4

Cyto Image 4 of 4

Histology

A tru-cut biopsy was subsequently done on the submandibular lesion. Sections show cores of tissue infiltrated by malignant tumour. This is composed of cells in both sheets and as single infiltrating cells. The cells show nuclear pleomorphism with occasional mitoses. Some cells are multinucleated with the nuclei in a "floret" like arrangement. Other cells have eccentrically placed nuclei and abundant eosinophilic glassy cytoplasm i.e. rhabdoid cells.

Histo Image 1 of 2

Histo Image 2 of 2

Immunohistochemistry

Immunohistochemical staining has given the following results:

Discussion

Rhabdomyosarcoma arises from primitive mesenchymal cells, and is the most common soft-tissue sarcoma of children. The head and neck are the most common locations, particularly the orbit, ear and nasal passages. Rhabdomyosarcomas are aggressive tumours characterised by rapid growth and metastases to lung and viscera, and differential diagnoses include lymphomas, neuroblastoma and Ewings sarcoma.

Three types of rhabdomyosarcoma, plus mixtures, are recognised; embryonic, alveolar, and pleomorphic types. Tsokos described the morphology of embryonic type to be more favourable than alveolar and other subtypes [Tsokos: 1992].

This case contains cellular features, in addition to the classic small blue cells, multinucleated giant myoblastic or strap cells and floret cells helping to differentiate the rhabdomyosarcoma from other small round cell tumours. DeMay described floret cells as giant tumour cells, with a central group or peripheral wreath of nuclei and pale cytoplasm [DeMay: 1996].

Although we haven't sub-typed this tumour, the differentiation between a embryonic- and alveolar rhabdomyosarcoma is that floret cells, where "alveoli" like formation is typical, is more common in alveolar subtypes.

References

• Richard M DeMay; The art and Science of Cytopathology; Volume II; ASCP; 579-581; 1996.
• Tsokos M, Webber BL, Parham DM, et al; Rhabdomyosarcoma: A new classification scheme related to Prognosis; Arch Pathol lab med 116: 847-855; 1992

Thanks to Herman for submitting this case