Gastrointestinal cytopathology

Gastrointestinal cytopathology, also known as GI cytology, is a relatively small part of cytopathology.

This article deals only with gastrointestinal cytopathology. An introduction to cytopathology is in the cytopathology article. Histopathology of the gastrointestinal tract is dealt with in gastrointestinal pathology.

Liver

Brief DDx:

• Metastatic adenocarcinoma, usu. colorectal adenocarcinoma.
• Hepatocellular carcinoma.

Others:

• Cholangiocarcinoma - usu. adenocarcinoma NOS, i.e. non-specific.
• Epithelioid hemangioendothelioma.
• Angiomyolipoma.

Normal liver

Cytology

Features:

• Hepatocytes:
  • Abundant cytoplasm
  • central nucleus +/- binucleation.
  • +/-Yellow granular pigment (bile).
• Bile ductules between adjacent cells.

Hepatocellular carcinoma

Main article: Hepatocellular carcinoma

Cytology

Features:

• Architecture - single cells and large clusters:
  • Cohesive clusters of cells (hepatocytes) surrounded by endothelial cells - diagnostic.
  • Capillaries traversing the fragments.
• Cells:
  • Central nucleus +/-prominent nucleoli, +/-nuclear inclusions.
  • +/-Multinucleation.
  • +/-Yellow cytoplasmic pigment (bile).
  • +/-Nuclear atypia.
  • +/-High NC ratio.

Notes:

• Low grade HCC is composed of cytologically normal appearing cells; the arrangement is what is diagnostic of malignancy.
• Fibrolamellar HCC has very large cells.

Images:

• HCC cytology (flickr.com/euthuman).
• HCC cytology (ouhsc.edu).

Cholangiocarcinoma

Main article: Cholangiocarcinoma

Cytology

Features:

• Looks like an adenocarcinoma:
  • Eccentric nuclei, one nucleolus per cell, abundant cytoplasm, nuclear size var. cell-to-cell, irregular nuclear membrane, irregular/uneven chromatin pattern.

Epithelioid hemangioendothelioma

Main article: Epithelioid hemangioendothelioma

General

• Rare.

Cytology

Features:

• Large atypical cells with:
  • Nuclear inclusions
  • Moderate cytoplasm.
  • +/-Multinucleation.

IHC

• Factor VIII +ve.

Common bile duct

Normal:

• Monolayer of small blue cells.

Notes:

• Caution is advised when calling malignancy in the setting of a stent or stones.

Adenocarcinoma

Features:

• Hyperchromasia.
• Pencil-shaped nuclei.
• Nuclear membrane irregularities.

Images:

• Colorectal adenocarcinoma - low mag. (WC).
• Colorectal adenocarcinoma - intermediate mag. (WC).

Stomach

Normal stomach

General

• Important as it may be a contaminant in a pancreatic FNA.

Cytology

Features:

• Bland cells with round nuclei.
• Granular cells with red cytoplasm (on Pap stain) - parietal cells - distinctive.

Note:

• May be difficult to distinguish from pancreas ductal epithelium.

Small bowel

Epithelium:

• Small blue cells.
• Goblet cells - key feature.

Notes:

• May appear to be similar to stomach and pancreatic duct.

Esophagus

• Cytology may be done to look for candida.
  • Report should comment on the presence of candida - if it is seen.

A short DDx:

• Barrett's esophagus.
• Candida.
• HSV.
• GIST.

Pancreas

A short DDx:

• Normal:
  • Duct.
  • Acini.
• Cystic lesions:
  • Serous cystadenoma of the pancreas.
  • IPMN.
  • Mucinous cystadenoma of the pancreas.
  • Solid pseudopapillary neoplasm.
• Others:
  • Ductal carcinoma of the pancreas.
  • Pancreatic neuroendocrine tumour.

Normal pancreas

Cytology

Features - duct:

• 2-D sheet of cells - equally spaced.
• Moderate-to-abundant cytoplasm.

Features - acini:

• Clustered cells +/- nuclear overlap.
• Round bland nuclei.
  • Small nucleoli.
• Moderate cytoplasm.

Pancreatic pseudocyst

General

• Symptomatic, e.g. abdominal pain.
  • Asymptomatic pseudocysts are typically observed, as a large number resolve spontaneously.
• Classically associated with pancreatitis secondary to alcohol.
• Pathologic diagnosis of exclusion.

Cytology

Features:

• Histiocytes.
  • Should be paucicellular otherwise.
• Necrotic debris - granular.

Note:

• Pseudocysts, by definition, do not have an epithelial lining.
• Luminal GI tract contamination - may lead to confusion with mucinous neoplasm.

DDx:

• Mucinous neoplasm.
• Serous neoplasm.

Serous neoplasm

General

• May be associated with von Hippel-Lindau syndrome.
• Usu. body or tail.
• Classically have a central stellate scar - seen radiologically.

Cytology

Features:

• Cuboidal/flat cells in clusters or sheets.
• +/-Nuclear grooves.

Stains

• PAS +ve.
• PASD -ve.

Mucinous neoplasm

General

• Pancreatic head: classically IPMN.
  • IPMN assoc. with colloid carcinoma.
• Pancreatic body & tail: mucinous tumour.

Cytology

Features:

• Clusters or sheets of mucinous cells.
• +/-Nuclear atypia.
• +/-Thick mucin.
  • Suggestive of IPMN.

Notes:

• In the body & tail mucinous cells may be contamination from the stomach.
  • Lesions in the pancreatic head are approached from the duodenum - do not have this problem.
• Ovarian stroma is not seen on cytology.
• Thick mucin may be from stomach.

Image:

• Mucin (ouhsc.edu).

Solid pseudopapillary neoplasm

Main article: Solid pseudopapillary neoplasm

• Abbreviated SPN.

General

• Young women.
• Tail of pancreas.

Cytology

Features:

• Papillary formations - composed of small cells with:
  • Scant cytoplasm.
  • +/-Nuclear grooves.
• +/-Cholesterol clefts.

Note:

• There are no true papillae in SPN.

DDx:

• Pancreatic pseudocyst.
• Pancreatic neuroendocrine tumour - single cells, classically plasmacytoid.

IHC

• PR +ve.
• Beta-catenin +ve.
• CD10 +ve.

Others:

• Chromogranin A -ve.

Pancreatic neuroendocrine tumour

Main article: Pancreatic neuroendocrine tumour

• Previously known as islet cell tumour of the pancreas.

General

• Classically solid.
  • May be cystic.

Cytology

Features:

• Round nuclei with salt and pepper chromatin.
  • Moderate nuclear size variation.
• Classically single cells with plasmacytoid morphology.

DDx:

• Solid pseudopapillary neoplasm.

IHC

• Chromogranin A +ve.
• Synaptophysin +ve.

Pancreatic adenocarcinoma

Main article: Invasive ductal carcinoma of the pancreas

• AKA ductal carcinoma.

Cytology

Features:

• Single cells.
  • Should be present.
• Monolayer of irregularly spaced cells - described as "drunken honeycomb".
• Nuclear atypia +/-grooves, +/-chromatin clearing.
  • Significant atypia: >=4:1 ratio between the nuclear diameter of cells.

Image:

• Pancreatic adenocarcinoma - marked nuclear atypia - low mag. (flickr.com/euthman).
• Pancreatic adenocarcinoma - marked nuclear atypia - high mag. (flickr.com/euthman).
• Pancreatic adenocarcinoma - drunken honeycomb - low mag. (flickr.com/euthman).
• Pancreatic adenocarinoma - drunken honeycomb - high mag. (flickr.com/euthman).

Acinar cell carcinoma

Main article: Acinar cell carcinoma of the pancreas

General

• Very rare.

Cytology

Features:

• High cellularity - important feature.
• Lack of ducts.
• Single cells and small cell clusters with abundant granular (metachromatic) cytoplasm - similar to normal pancreatic acini.
• Naked nuclei.

Note:

• Considered to be a difficult diagnosis.

See also

• Cytopathology.
• Gastrointestinal pathology.