Mast cell diseases comprise a spectrum of disorders including cutaneous mastocytosis, indolent or aggressive systemic variants including leukemia, and unifocal tumor formations such as benign extracutaneous mastocytoma or aggressive mast cell sarcoma (MCS). Many mast cell diseases are associated with aberrancy of c-KIT proto-oncogene resulting in tyrosine kinase activity, typically exhibiting point mutation in codon 816. MCS is an exceedingly rare clinicopathologic entity characterized by a unifocal accumulation of neoplastic mast cells that grow in a locally destructive manner. We report a case in a 2-year-old boy who was initially diagnosed at 8 months of age with atypical cutaneous mastocytoma of the right ear with subsequent aggressive, destructive growth pattern; features that were most consistent with MCS. So far, MCS has been documented in the literature in at least 6 human cases. To the best of our knowledge, our case represents the first MCS in an infant. Thorough multimodal approach with strict follow-up is relevant in appropriately diagnosing this rare entity, particularly in differentiating this lesion from other neoplasms that are more likely to occur in infancy.
Departments of *Pathology and Laboratory Medicine
†Pediatric Hematology and Oncology, Loma Linda University Medical Center, Loma Linda, CA
‡Clarient Inc., Aliso Viejo, CA
M.B.Q., C.L.B., A.K., C.W.Z., E.H.R., L.W., and J.W.: participated in the composition of this case report. M.B.Q., C.L.B., C.W.Z., E.H.R., L.W., and J.W.: interpreted the morphologic, special stains and IHC findings, performed literature search and review, and procured photomicrographs. C.W.Z.: interpreted the EM findings. E.H.R.: interpreted the flow cytometry data and provided the scattergrams. A.K.: presented additional relevant clinical information.
The authors declare no conflict of interest.
Reprints: Jun Wang, MD, Department of Pathology and Laboratory Medicine, Room 2516, 11234 Anderson Street, Loma Linda, CA 92354 (e-mail: firstname.lastname@example.org).
Received December 16, 2011
Accepted July 25, 2012