Tubular and ⁄or villous adenoma

Author: Mikael Häggström

Gross evaluation

Further information: Colon

Tissue selection and trimming

There is a separate article for the Grossing of minimally invasive colorectal surgery.

Depending on sample format:

• Biopsies and polyps of <4 mm are embedded in their entirety. Samples less than 0.3 mm should be stained with eosin to avoid getting lost processing.
• Polyps 4-8 mm with short stem or without stem: Identify the excision surface and divide the polyp longitudinally through the excision surface.
• Polyps > 8 mm with a stem long enough to make it possible to take a transverse, whole slice from the stem closest to the excision surface: First, take a transverse slice through the peripheral portion of the stem, encompassing the entire circumference. Then take a 3-4 mm thick slice longitudinally through the polyp and the middle of the stem, after which the two remaining parts on either side are cut into equally thick slices, parallel to the previous slice.
• Polyps >8 mm with short stem or without stem: Identify the excision surface and cut out a 3-4 mm thick disk that extends longitudinally through the center of the excision surface. Then divide the two remaining portions into equally thick slices, parallel to the previous slice.
• Polyps that come in parts: Pick out the largest pieces, which are cut as similar as possible to above. Small fragments are sieved and embedded in a separate box.

Gross reporting

• Polyp and/or fragment sizes
• Presence or absence of stem of polyps

Example, for a gastrointestinal biopsy:

Labeled: "Sigmoid colon biopsy". The specimen is received in formalin and consists of 4 fragments of pink-tan tissue with a vaguely recognizable mucosal surface, mixed with food-like material. The fragments measure 0.2-0.3 cm in greatest dimension. The entire specimen is submitted for microscopic examination in one cassette.

Microscopic evaluation

Criteria

Tubular adenoma with low-grade dysplasia.

Dysplastic changes should involve at least the upper half of the crypts and the luminal surface.

• Nuclear dysplasia is mandatory to diagnose adenoma. It involves:

• Nuclear atypia: Enlarged hyperchromatic nuclei (that is, dark purple) that are oval or frequently elongated, and with high nucleus to cytoplasm ratio.
• Other cellular atypia: Often nuclear stratification, nuclear crowding (that is, nuclei are bunched-up) and loss of polarity

• Always changes in gland architecture, such as:

• Enlarged crypts
• Gland budding, or otherwise irregular glands

• Mucin depletion is often seen, but is not required
• Goblet cell reduction.

Differential diagnoses

Hyperplastic polyp

Hyperplastic polyp	Tubular adenoma
Nu dysplasia	Dysplasia
Proliferative epithelium restricted to base	Proliferative epithelium present at the surface
Gland lining cells mature at the surface	No surface maturation

• 

  Non-proliferative (left) versus proliferative (large at right) colonic crypts, where the latter's proximity to the surface confers a diagnosis of a tubular adenoma.

• 

  In nuclear crowding, also look for inflammation: Here a hyperplastic polyp with inflammatory reactive changes, reminiscent of adenoma.

Colorectal carcinoma

Colorectal adenocarcinoma (in this case, not otherwise specified).

Colorectal carcinoma (mainly adenocarcinoma) is distinguished from an adenoma (mainly tubular and ⁄or villous adenomas) mainly by invasion through the muscularis mucosae.

Also, carcinoma also commonly displays:

• Varying degrees of gland formation with tall columnar cells
• Frequenty desmoplasia
• Dirty necrosis, consisting of extensive central necrosis with granular eosinophilic karyorrhectic debris. Garland of cribriform glands are frequently found in their vicinity.

Low or high grade

In low-grade lesions, the crypts should maintain a resemblance to normal colon.

High-grade dysplasia:
-Substantial stratification
-Nuclear pleomorphism
-Atypical mitoses
-Increased nucleus to cytoplasm ratio
-Prominent nucleoli

Typical findings in low-grade versus high-grade tubular and ⁄or villous adenoma

	Low-grade	High grade
Crowding	Pseudo-stratification to early stratification	More substantial stratification
Nuclear pleomorphism and atypical mitoses	Absent or minimally present	Present
Loss of cell polarity	Minimal	More significant
Crowding, cribriform, or complex architecture	No significant	Present

High grade lesions also typically have:

• Cribriform architecture, consisting of juxtaposed gland lumens without stroma in between, with loss of cell polarity. Rarely, they have foci of squamous differentiation (morules). This should be distinguished from cases where piles of well-differentiated mucin-producing cells appear cribriform. In such piles, nuclei show regular polarity with apical mucin, and their nuclei are not markedly enlarged.
• Increased nucleus to cytoplasm ratio.
• More "open" appearing nuclei with increasingly prominent nucleoli
• Back-to-back glands

• 

  Tubular adenoma with high-grade dysplasia.

Tubular or villous

Colorectal adenoma

Type	Histopathology	Image
Tubular adenoma	Over 75% of volume has tubular appearance.
Tubulovillous adenoma	25%-75% villous
Villous adenoma	Over 75% villous

Length of villi must be at least twice the depth of the normal mucosal thickness.

Further information: Evaluation of tumors

Further workup

Look for and evaluate any lymph nodes in the tissue specimen, for possible malignancy.

Dissecting pools of mucin at the base of any adenoma should be evaluated for the possibility of mucinous carcinoma.

Report

• Tubular, tubulovillous or villous adenoma.
• Any high-grade component (whereas low-grade does not need to be stated in the report as it is presumed otherwise).
• ((Adenoma size))
• ((Whether it is radically resected.))

If any lymph nodes are found in the tissue sample, report the presence or absence of malignancy in any of them.

Example:

Sigmoid colon polyp x2, polypectomies: One tubular adenoma and one tubulovillous adenoma.

  See also: General notes on reporting

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