Researchers reported a unique case of concurrent retroperitoneal mast cell sarcoma (MCS) and systemic mastocytosis (SM) with an undisclosed associated hematological neoplasm. The case report, published in Clinical Pathology, noted additional suspicion of a clonal myeloid neoplasm based on karyotype and hemogram data.

“Mast cell sarcoma is an exceedingly rare variant of mastocytosis identified by morphologically atypical mast cells that are locally destructive and highly aggressive,” the authors wrote. “Despite unknown bone marrow status at disease burden, it is worth noting that our case draws attention to a subvariety of SMs that may progress to MCS, rapidly accompanied by the existence of an [associated] hematological neoplasm.”

The 23-year-old pseudohermaphrodite patient presented with unexplained abdominal pain, recurrent flushing, palpitation, and shock. Prior hormone replacement therapy led to no improvement.

Abdominal magnetic resonance imaging revealed peritoneal masses, and the initial biopsy was mistakenly interpreted as spermatocytic seminoma. A cycle of chemotherapy for spermatocytic seminoma was attempted with no improvement; therefore, a second biopsy was performed, leading to the diagnosis of MCS and SM. The patient’s condition declined rapidly, and the family refused a bone marrow aspiration. She died shortly thereafter.

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The authors note that diagnosing MCS is challenging due to its heterogeneous nature, even from site to site in the same patient. The clue in helping correct the misdiagnosis of spermatocytic seminoma was the finding of diffuse mast cell infiltration in the second ovarian biopsy sample. In addition, MCS can mask the presence of aggressive SM, which occurred in this case.

Due to the complexity and heterogeneity of mast cell disorders, the authors recommend a collaborative multidisciplinary approach for the diagnosis and optimal treatment of these patients.


Chen I, Liao JB, Lin JC, Hsieh PP, Hsieh MY. Mast cell sarcoma of the retroperitoneum with concurrent systemic mastocytosis and an undisclosed associated hematologic neoplasm: a case report. Clin Pathol. Published online September 13, 2022. doi:10.1177/2632010X221123539