Diffuse Large B-Cell Lymphoma Transdifferentiating Into Histiocytic Sarcoma: Case Report + Systematic Review.

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Diffuse large B-cell lymphoma (DLBCL) is an aggressive non-Hodgkin lymphoma.
• Cutaneous involvement in DLBCL can manifest as various skin lesions.
• Histiocytic sarcoma (HS) is a rare malignancy of myeloid or histiocytic origin.

Purpose of the Study:

• To report a unique case of cutaneous histiocytic sarcoma (HS) arising in a patient with a history of diffuse large B-cell lymphoma (DLBCL).
• To investigate the potential link between DLBCL and HS through genetic analysis.
• To review existing literature on cutaneous HS with underlying hematologic malignancies.

Main Methods:

• Clinical presentation and histopathologic examination of a patient with a rapidly growing skin tumor.
• Immunophenotypic characterization of tumor cells.
• Genetic analysis (KRAS mutation detection) of DLBCL and HS specimens.
• Systematic literature review of cutaneous HS cases.

Main Results:

• Histopathology confirmed cutaneous histiocytic sarcoma (HS) in a patient with prior diffuse large B-cell lymphoma (DLBCL).
• Identical p.G13D KRAS mutations were found in both the DLBCL and HS specimens, suggesting a common origin.
• Literature review identified only two prior cases of cutaneous HS with underlying hematologic transdifferentiation.

Conclusions:

• This case represents the first documented instance of systemic DLBCL with cutaneous involvement transdifferentiating into cutaneous HS, supported by identical KRAS mutations.
• The findings highlight a rare phenomenon of histiocytic transdifferentiation in the context of hematologic malignancy.
• Distinct clinical and pathological features underscore the unique nature of this case.