Immunohistochemical Staining for Disseminated Carcinomatosis of the Bone Marrow in a Patient with Post-Colonoscopy Colorectal Cancer: A Case Report.

[INTRODUCTION] The incidence of disseminated carcinomatosis of the bone marrow (DCBM) associated with colorectal cancer is low, but it can rapidly progress and cause even death. A previous study has suggested a relationship between mucin profiles and the prognosis of colorectal cancer. However, there are no reports of mucin staining in cases of DCBM with post-colonoscopy colorectal cancer (PCCRC).

[CASE PRESENTATION] A 58-year-old man who had undergone colonoscopy (CS) 1 year ago complained of fatigue and fever. The man was diagnosed with virus-associated hemophagocytic syndrome and received steroid pulse therapy. Despite treatment, his condition deteriorated. F-fluorodeoxyglucose positron emission tomography-computed tomography revealed diffuse uptake in the bone marrow. A bone marrow biopsy revealed atypical CK20-positive and CK7-negative cellular nests, suggesting a primary gastrointestinal tumor. Subsequent CS at our hospital revealed a 30-mm type 4 transverse colorectal cancer lesion. Thus, the patient was diagnosed with DCBM associated with PCCRC. The patient died 18 days after his last CS. Mucin staining revealed that the cancer cells were MUC2-positive and MUC5AC-negative. MUC5AC negativity has been associated with poor prognosis in colorectal cancer and may have suggested rapid disease progression.

[CONCLUSION] The mucin staining result of MUC5AC negativity suggested rapid disease progression and poor prognosis in this case.