This case report describes a 58-year-old patient with a history of multiple kidney transplantations who was found on follow-up imaging to have a tumour-like soft-tissue mass adjacent to the graft kidney. Biopsy of the lesion demonstrated extramedullary hematopoiesis with trilineage hematopoietic elements and without dysplastic changes or an increased blast population. The patient had no peripheral blood count abnormalities suggesting bone marrow disease. The authors emphasize the importance of distinguishing extramedullary hematopoiesis from myeloid sarcoma, because the latter represents a manifestation equivalent to acute myeloid leukemia (AML) and mandates different treatment and prognostic considerations.
The reported patient was middle-aged (58 years) and had undergone multiple renal transplantations. The lesion was identified during routine post-transplant surveillance imaging. No blood count abnormalities consistent with an underlying bone marrow disorder were detected in this patient prior to or at the time of lesion evaluation. The original report does not provide additional demographic details, comorbidities, or the exact number and timing of transplantations beyond stating multiple renal transplants.
Follow-up imaging revealed a tumour-like mass in the soft tissues near the graft kidney. The imaging work-up raised concern for a neoplastic process, prompting tissue sampling. The source does not report detailed imaging modalities, measurements, or radiologic characteristics beyond the description of a soft-tissue lesion suspicious for tumour adjacent to the transplanted kidney.
Tissue biopsy of the soft-tissue lesion demonstrated extramedullary hematopoiesis. Histopathology showed a trilineage hematopoietic proliferation without dysplastic features and without an increase in blasts. The report explicitly states the absence of blast proliferation and dysplasia in the sampled lesion. No bone marrow biopsy results are described, and peripheral blood counts showed no abnormalities suggestive of marrow disease. The source does not report immunophenotypic, cytogenetic, or molecular testing results for the lesion.
From a prognostic and therapeutic standpoint, the critical differential diagnosis is between extramedullary hematopoiesis and myeloid sarcoma. Extramedullary hematopoiesis denotes reactive or clonal trilineage hematopoietic activity occurring outside the bone marrow. It may arise in the setting of an underlying neoplastic bone marrow disorder but can also be reactive. In contrast, myeloid sarcoma is characterized by a predominance of myeloid blasts; when the myeloid blast proportion exceeds 20%, the lesion is essentially equivalent to acute myeloid leukemia (AML). Because myeloid sarcoma represents localized AML, its detection typically prompts systemic AML-directed treatment rather than conservative management.
The case report highlights that the lesion lacked dysplasia and blast increase, supporting a diagnosis of extramedullary hematopoiesis rather than myeloid sarcoma. Clinicians and pathologists must perform careful morphologic assessment and correlate with peripheral blood and bone marrow findings to avoid misdiagnosis.
In the described patient, the lesion was asymptomatic. The report states that asymptomatic extramedullary hematopoiesis may be managed with clinical and radiologic follow-up. If the lesion is symptomatic, options include drug therapy or local radiation therapy. By contrast, a diagnosis of myeloid sarcoma (myeloid blasts >20%) is effectively a presentation of AML and should be treated accordingly with systemic therapy. The source does not provide specific drug regimens, radiation dosing, or follow-up intervals.
This case underscores several practical points for clinicians evaluating tumour-like lesions in patients with a history of solid-organ transplantation. First, not all graft-adjacent masses are neoplastic in the classic sense; extramedullary hematopoiesis can present as a tumour-like soft-tissue lesion. Second, accurate histopathologic assessment to exclude increased blasts or dysplasia is essential because the distinction from myeloid sarcoma changes management and prognosis substantially. Third, in the absence of systemic hematologic abnormalities or pathologic features of AML, conservative surveillance is an appropriate approach for asymptomatic extramedullary hematopoiesis, whereas symptomatic lesions may warrant systemic treatment or local radiation. Finally, the report does not supply details on imaging characteristics, immunophenotyping, cytogenetics, or long-term outcomes for this patient, and those data were not reported in the source.
Keywords from the original report include: acute myeloid leukemia; extramedullary hematopoiesis; myeloid sarcoma; kidney transplantation.