Mast cell sarcoma: a rare and potentially under-recognized diagnostic entity with specific therapeutic implications

Abstract

Mast cell sarcoma is a rare, aggressive neoplasm composed of cytologically malignant mast cells presenting as a solitary mass. Previous descriptions of mast cell sarcoma have been limited to single case reports, and the pathologic features of this entity are not well known. Here, we report three new cases of mast cell sarcoma and review previously reported cases. Mast cell sarcoma has a characteristic morphology of medium-sized to large epithelioid cells, including bizarre multinucleated cells, and does not closely resemble either normal mast cells or the spindle cells of systemic mastocytosis. One of our three cases arose in a patient with a remote history of infantile cutaneous mastocytosis, an association also noted in one previous case report. None of our three cases were correctly diagnosed as mast cell neoplasms on initial pathological evaluation, suggesting that this entity may be under-recognized. Molecular testing of mast cell sarcoma has not thus far detected the imatinibresistant KIT D816V mutation, suggesting that recognition of these cases may facilitate specific targeted therapy.

Paediatric mastocytosis: a systematic review of 1747 cases

“…Tryptase levels were available for 403 patients . Alvarez‐Twose demonstrated that serum tryptase levels > 20 ng mL −1 were correlated with extensive skin involvement, but not always associated with systemic forms .…”

“…Mutations in exon 17 including D816V were detected in 34% of patients . Mutations outside exon 17 were found in 18% of cases (Del419, F522C, ITD502–503, K509I, M541L, L852L) . In 48% of cases, KIT mutational status was mentioned as wild‐type .…”

“…Mutations outside exon 17 were found in 18% of cases (Del419, F522C, ITD502–503, K509I, M541L, L852L) . In 48% of cases, KIT mutational status was mentioned as wild‐type . Whole KIT gene sequencing data were only rarely available for those cases with wild‐type genotype (29 of 103, 28%) .…”

“…In these cases, the disease may remain active throughout adolescence, with a risk of systemic disease in adulthood. Finally, some rare but very severe forms of mastocytosis, such as mast cell sarcoma (MCS) and mast cell leukaemia (MCL), are reported in children . Factors predicting the course and severity of childhood‐onset mastocytosis have not yet been completely identified.…”

KIT mutation analysis in mast cell neoplasms: recommendations of the European Competence Network on Mastocytosis

“…Other non codon 816 KIT mutations can be found{Ryan, 2013 #45;Kim, 2013 #42;Georgin-Lavialle, 2013 #301}…”