粘液癌（mucinous adenocarcinoma；muc）とは主として細胞外に多量の粘液を産生し，粘液の結節（extracellular mucin）を形成する癌であり，全大腸癌の4%程度を占める1）．大腸癌取扱い規約 第9版2）に従えば，粘液結節（粘液湖mucinous poolとも言う）を形成する領域が面積的に最も優勢像である腫瘍をmucと診断し，他の組織型を含む場合は優勢像から列記する（例：mucinous adenocarcinoma，muc>tub1>tub2>pap）．WHO分類3）では，そのような領域が50%を超える腫瘍をmucinous adenocarcinomaと呼ぶ．
mucには高分化型腺癌（乳頭腺癌，高分化管状腺癌，中分化管状腺癌）に由来する高分化型mucと，低分化型腺癌（非充実型低分化腺癌，印環細胞癌）に由来する低分化型mucとがある2）とされているが，一般型の腺癌（adenocarcinoma，NOS）と比べると右側結腸に発生する頻度が高く，虫垂の浸潤癌でもmucの占める割合が高い．Lynch症候群や炎症性腸疾患に関連して発生することの多い組織型でもある．
mucinous tumours are more common in the proximal colon and exhibit specific molecular features including DNA mismatch repair deficiency (dMMR) [8,9,10,11,12,13,14,15,16], BRAF mutation [10, 13,14,15,16] and a high-frequency of CpG island methylator phenotype (CIMP-high) [10, 13, 16]. Mucinous CRC has further been negatively associated with p53 overexpression
予後は良い？悪い？も結論なし
While some studies have reported that mucinous tumours have a worse prognosis than non-mucinous tumours [2, 6, 12, 19, 23], others have found no difference
Histologic grading of mucinous CRC is challenging. Conventionally,
colorectal adenocarcinoma is graded based on the degree of glandular differentiation,
with cases exhibiting ?50% gland formation being considered as high grade
World Health Organisation (WHO) 4th Edition guidelines (2010) recommended
that mucinous CRCs should instead be graded based on MMR status, with pMMR
tumours considered as high grade
mucでは「MMRが正常」＝「High Grade」に」になる？？？
次のガイドラインでは「削除」されて、graded based on the degree of glandular differentiationに、戻った
High density of tumour infiltrating lymphocytes (TILs) as determined by histopathological examination has been associated with lower rates of recurrence and longer patient survival in multiple studies