Soft tissue sarcoma with complex membranous and microtubular inclusions.

Area of Science:

• Cell Biology
• Pathology
• Electron Microscopy

Background:

• Undifferentiated sarcomas can exhibit complex cytoplasmic inclusions.
• Certain inclusions like microtubular reticular structure (TRS) and tubular confronting cisternae (TCC) are associated with specific viral infections and autoimmune diseases.

Observation:

• A 67-year-old woman's undifferentiated sarcoma, originating in paraspinal adipose tissue, displayed complex cytoplasmic inclusions in most tumor cells.
• Four distinct morphologic types of inclusions were identified: intracisternal TRS and TCC, and cytoplasmic crystalline microtubular arrays and smooth endoplasmic reticulum (SER) complexes.
• The smooth endoplasmic reticulum (SER) inclusions were uniquely complex, differing from previously described structures.

Findings:

• The observed inclusions included intracisternal microtubular reticular structure (TRS) and tubular confronting cisternae (TCC).
• Cytoplasmic inclusions consisted of crystalline microtubular arrays and complex smooth endoplasmic reticulum (SER) structures.
• The patient had no known conditions typically associated with TRS and TCC, such as lupus or viral infections.

Implications:

• The presence of these complex inclusions in sarcoma, without typical associated pathologies, presents a novel finding in tumor biology.
• Further research is needed to elucidate the formation, function, and biological significance of these unique cytoplasmic structures in mesenchymal tumors.
• This case highlights the diverse and sometimes unexpected ultrastructural features that can arise in neoplastic cells.