Lymphocytic Colitis
Definition
- Colorectal disease characterized by an intramucosal chronic inflammatory infiltrate in the absence of crypt distortion
Alternate/Historical Names
- Microscopic colitis
- Used by some to refer to both lymphocytic and collagenous colitis, while to others it refers to only lymphocytic colitis
Diagnostic Criteria
- Increased lymphocytes and plasma cells in lamina propria
of colon
- Increased eosinophils and mast cells may also be seen in lamina propria
- Increased intraepithelial lymphocytes in surface epithelium between crypts
- >20 / 100 epithelial cells
- Normal is 5 / 100
- Mucosa overlying lymphoid nodules must be excluded from evaluation
- T cell phenotype
- May also involve crypts
- A rare cryptal variant has been described
- Increased intraepithelial lymphocytes only in crypts, not the surface epithelium
- Same behavior as usual lymphocytic colitis
- Increased intraepithelial lymphocytes only in crypts, not the surface epithelium
- Paucicellular lymphocytic colitis has been proposed
(Goldstein 2004)
- 11 intraepithelial lymphocytes / 100 epithelial cells
- Same behavior as usual lymphocytic colitis
- It has been proposed that this is a different entity (Fernandez-Banares 2009)
- We prefer to diagnose this as “colonic intraepithelial lymphocytosis” with a comment
- >20 / 100 epithelial cells
- Surface mucosa typically flattened, mucin depleted
- Focal detachment may be seen
- No overt ulceration
- Occasional neutrophils up to cryptitis may be seen in up to 38% of cases
- Infrequently focally prominent with crypt abscesses
- If present, infection and inflammatory bowel disease must be ruled out
- Infrequently focally prominent with crypt abscesses
- Multinucleated giant cells may be seen in rare cases
- Located immediately below the surface epithelial layer
- No significant crypt distortion
- Mild crypt irregularity has been described in 4% of cases
- May be variably distributed in colon
- A single normal biopsy does not rule out the disease
- No thickened subepithelial collagen layer
- Terminal ileum may be involved by intramucosal lymphocytosis
- Normal levels reported from 2-8 T cells / 100 enterocytes
- Several other GI diseases must be ruled out (see Differential Diagnosis)
- Lymphocytic colitis and collagenous colitis have been proposed to be related
- They share an identical chronic inflammatory pattern and are distinguished only by the presence of a thickened collagen layer only in the latter
- Cases are reported showing change from one to the other on sequential biopsies
- Collagen deposition in collagenous colitis may be patchy, making interpretation of such observations difficult
- Female:Male ratios originally reported as different
- More recent studies find similar ratios of approximately 1-5:1 F:M (Kao 2009)
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 11/11/09, 12/3/09, 11/11/11, 1/28/12
