Collision-type adenosquamous carcinoma of the colon with signet-ring adenocarcinoma: A rare case report.

INTRODUCTION AND IMPORTANCE

Adenosquamous carcinoma (ASC) of the colon is a rare malignancy, representing approximately 0.06 % of colorectal cancers (CRC). It is characterized by the coexistence of adenocarcinoma and squamous cell carcinoma components.

CASE PRESENTATION

Here, we present a unique case of a 47-year-old male diagnosed with collision-type ASC, featuring both signet-ring adenocarcinoma and squamous cell carcinoma. The patient presented with abdominal pain and distension, and imaging revealed multiple colonic strictures and lymphadenopathy. Surgical intervention included an extended left hemicolectomy. Histopathology confirmed the presence of two distinct tumor components, with no evidence of lymph node metastasis. Immunohistochemistry was positive for p63 in the squamous cell component, while HPV DNA testing was negative.

CLINICAL DISCUSSION

ASC is known for its aggressive clinical course and poor prognosis compared to adenocarcinoma. Although rare, its clinical and histopathological features are important for guiding management.

CONCLUSION

This case represents the first reported instance of a collision-type colon ASC with a signet-ring adenocarcinoma component. The patient is currently undergoing neoadjuvant chemotherapy with the modified FOLFOX6 regimen and responding well. Further research is required to elucidate the molecular mechanisms underlying ASC and improve therapeutic outcomes.