CROCC-mutated rhabdoid colorectal carcinoma showing in intercellular spaces lamellipodia and cellular projections revealed by electron microscopy.

BACKGROUND

Rhabdoid colorectal carcinoma (RC) is a rare lesion localized to the proximal colon of patients with a mean age at diagnosis of around 70 years. This tumor shows an aggressive behavior with an overall survival period shorter than 12 months. The diagnostic hallmark is the presence of rhabdoid cells. Alterations in chromatin remodeling (SMARCB1) and in the centrosome structure (CROCC) are reported in RC usually BRAF and MSI-H. RKO intestinal neoplastic cells culture (BRAF, SMARCB1, MSI-H) with CROCC knockdown exhibit rhabdoid features and develop prominent projections from the edge of the cell.

METHODS

Here, we investigated two cases of CROCCSMARCB1 RC by scanning and transmission electron microscopy (SEM, TEM).

RESULTS

TEM confirmed the diagnostic presence of intermediate cytoplasmic filaments and nucleolar margination. SEM showed cellular protrusions (lamellipodia) in the intercellular spaces not evident at light microscopy.

CONCLUSIONS

These protrusions CROCC-related might represent the pathogenetic mechanism underlying the rhabdoid aggressive behavior, independently of tumor staging. To our knowledge, the SEM technique was applied in the study of this neoplasm for the first time.