Rhabdoid

A "rhabdoid" refers to a specialized cell type or tumor characterized by cells that display features reminiscent of rhabdomyoblasts, which are immature skeletal muscle cells. The term is most commonly associated with rhabdoid tumors, aggressive malignancies that can occur in various parts of the body, including the brain, kidneys, and soft tissues.

Rhabdoid tumors are rare but highly malignant neoplasms that primarily affect children, although adult cases have been reported. They are classified as a distinct entity within the category of undifferentiated or poorly differentiated tumors due to their unique histological and molecular features. These tumors typically display cells with large, eccentric nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm containing whorled intermediate filaments.

The origin of rhabdoid cells is thought to be from pluripotent embryonic cells with the potential to differentiate along multiple lines, including muscle and neural pathways. Rhabdoid features can also be seen in certain benign and malignant tumors, such as rhabdoid melanomas and rhabdoid tumors of the kidney.

Diagnosis involves histopathological examination, often complemented with immunohistochemistry. Rhabdoid tumors usually exhibit loss of INI1 (SMARCB1) gene expression, which is a key molecular marker aiding in diagnosis. Due to their aggressive behavior, early detection and treatment strategies typically involve surgical resection combined with chemotherapy and radiation therapy.

In summary, "rhabdoid" describes a cellular appearance and tumor type characterized by distinctive morphological and molecular attributes, primarily associated with highly malignant neoplasms in pediatric populations.