Rhabdomyosarcomas, especially of alveolar rhabdomyosarcoma, have a propensity to metastasize to the bone marrow. Not infrequently, rhabdomyoblasts are mistaken for the blast cells of acute leukaemia.
Immunophenotyping usually shows these cells to be CD56+/CD45− and they express desmin, vimentin, myoglobin and MyoD1.
The cytogenetic hallmarks are the translocations t(2;13)(q35;q14)/PAX3-FOXO1 and t(1;13)(p36;q14)/PAX7-FOXO1, seen in approximately 60% and 20% of cases respectively.
References
Leukaemic alveolar rhabdomyosarcoma. Curry S, Bacon CL, Robinson I, Capra M, Smith OP. Br J Haematol. 2010 Aug 31. PMID: 20813011
Unusual leukemic presentation of rhabdomyosarcoma: report of two cases with immunological, ultrastructural and cytogenetical studies. Putti MC, Montaldi A, D’Emilio A, Sainati L, Milanesi C, Stella M, Zanesco L, Basso G. Haematologica. 1991 Sep-Oct;76(5):368-74. PMID: 1806439
Carcinocythemia in a patient with rhabdomyosarcoma. Maldonado A, Fradera J, Vélez-García E. Bol Asoc Med P R. 1991 Jan;83(1):13-6. PMID: 2039572