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Left sided appendicitis
Acute appendicitis as inflammatory mass
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Laparoscopic appendectomy
Contributed by Elliot Weisenberg, M.D. and Andrey Bychkov, M.D., Ph.D.
Fibrinopurulent exudate
Mucosal ulceration
Severe disease
Dark mucosa
Contributed by Qingqing Liu, M.D., Ph.D.
Appendiceal diverticulitis
Appendiceal endometriosis
Contributed by Raul S. Gonzalez, M.D. and Elliot Weisenberg, M.D.
Marked neutrophilic infiltration
Transmural inflammation
Intraluminal neutrophils
Periappendiceal abscess
Xantho-granulomatous
inflammation
Contributed by Bella Lingjia Liu, M.D.
CT of abdomen
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Adenocarcinoma involving appendiceal tip
Adenocarcinoma involving appendix
Contributed by Bella Lingjia Liu, M.D.
Mucinous adenocarcinoma
Appendiceal adenocarcinoma
Contributed by Bella Lingjia Liu, M.D.
Adenocarcinoma with adjacent LAMN
Infiltrative glands with desmoplasia
Tumor cells in mucin
Adenocarcinoma with adjacent TVA
Infiltrative glands in stroma
Cribriforming with necrotic debris
Lymphovascular invasion
Luminal obstruction
Signet ring cells
Contributed by Dr. Oleksandr Grygoruk, Boris Hospital and Medical Center, Kiev (Ukraine)
40 year old woman with prodromal measles confirmed by serology
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Warthin-Finkeldey cells (lymph node)
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Cecum, appendix and arteries
View from cecum
Contributed by Maryam Kherad Pezhouh, M.D., M.Sc.
Appendix
Contributed by Maryam Kherad Pezhouh, M.D., M.Sc.
Cross section of an appendix
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Acute appendicitis on CT
Contributed by Danielle Hutchings, M.D.
Dilatation and hyperemia
Serosal exudate
Perforation
Contributed by Danielle Hutchings, M.D.
Transmural mixed inflammatory infiltrate
Cluster of CMV infected cells
Intranuclear and intracytoplasmic inclusions
CMV infected cell
Positive CMV immunostain, endothelial cells
CMV immunostain, epithelial cell
Contributed by Dr. Michael Feely
Thick eosinophillic mucus distends the lumen of the appendix as well as individual crypts
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Oblique coronal
reformation of
contrast enhanced
CT scan
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Intraoperative image
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Multiple appendiceal diverticula
Congenital appendiceal diverticulum
Contributed by Qingqing Liu, M.D., Ph.D.
Multiple diverticula
Connection between diverticulum and main lumen
Inflamed diverticulum
Inflammatory exudate
Acute appendicitis accompanied by appendiceal diverticulitis
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Intraoperative pinworm
Enterobius vermicularis through appendix
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Inflamed appendix with stercolith
With retrieved worm
Enterobius vermicularis through appendix
Contributed by Eiman Adel Hasby, M.D. and Case #90
Appendix with luminal Enterobius
Enterobius in acute appenicitis
Appendicitis with luminal Enterobius
Enterobius eggs
Appendicitis with enterobiasis
Appendicitis with enterobiasis
Male Enterobius adult worm
Female Enterobius adult worm
Gravid female Enterobius worm
Enterobius eggs
Enterobius egg with larva
Eggs
Contributed by Bobbi Pritt, M.D. and Chamarajan Shrinivasan, M.D.
Wet mount from stool sample
Ova and larva of Enterobius vermicularis
Contributed by Centers for Disease Control and Prevention
Eggs
Contributed by Raul S. Gonzalez, M.D.
Obliterated lumen
Adipose and spindle cells
Bland spindle cells
Superimposed acute appendicitis
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Small GIST of appendix
Pedunculated cystic GIST
Pedunculated GIST after imatinib
Contributed by Raul S. Gonzalez, M.D.
Well circumscribed tumor
Bland spindle cells
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Small appendiceal GIST
Bland appendix GIST
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CT abdomen: dilated and inflamed appendix
CT / MRI: ovary and appendix
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Laparoscopic view of an inflamed appendix
Contributed by Raul S. Gonzalez, M.D.
Thickened wall
Extension into cecum
Contributed by Trang Lollie, M.D.
Concentric growth
Low grade growth pattern
High grade growth pattern
High grade growth pattern
Perineural invasion
Lymphovascular invasion
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Pleomorphic electron dense granules
Electron dense granules within mucin
Contributed by Maryam Kherad Pezhouh, M.D., M.Sc. and Masoumeh Peykan Heyraty, M.D.
Multiple granulomas
Focal necrotizing granuloma
Necrotizing granuloma
Well formed granulomas
Contributed by Aaron R. Huber, D.O.
Associated acute appendicitis
Serrated epithelium
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Abscess resolved after treatment
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Interval appendectomy
Contributed by Pu Ni, M.D. and Qingqing Liu, M.D., Ph.D.
Mildly enlarged appendix
Significantly enlarged appendix
Inflammatory polyp mimicking neoplasm
Contributed by Pu Ni, M.D., Qingqing Liu, M.D., Ph.D. and @RaulSGonzalezMD on Twitter
Granulomas and
xanthogranulomatous
inflammation
Xanthogranulomatous
inflammation
Granulomas
Mural fibrosis
Transmural chronic inflammation
Contributed by @RaulSGonzalezMD on Twitter (see original post here)">
tinyurl.com/2ndx69rz / #pathology #PathTwitter #gipath #PathOutPic"Contributed by @RaulSGonzalezMD on Twitter (see original post here)">
Interval appendicitis
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CT demonstrating an intraluminal tubular structure
Intraluminal protruding mass with central fat component
Cecal thickening without visualization of appendix
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Elongated lesion at appendiceal orifice
Tubular structure in cecum
Endoscopy
Contributed by Mahzad Azimpouran, M.D. and Danielle Hutchings, M.D.
Elongated tubular lesion
Inversion of appendiceal base
Associated with mucinous neoplasm
Serosal surface
Contributed by Mahzad Azimpouran, M.D. and Danielle Hutchings, M.D.
Dome shaped configuration
Polypoid configuration
Ganglion cell aggregates
Ganglion cells and nerves
Lymphoid aggregates
Appendiceal mucinous neoplasm
Contributed by @Andrew_Fltv on Twitter
LAMN and HAMN
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Mucocele: dilated appendix
Contributed by Raul S. Gonzalez, M.D. and Michael Feely, D.O.
Denuded LAMN
LAMN with loss of muscularis mucosae
LAMN with pushing invasion
HAMN
LAMN in cross section
Villous architecture in LAMN
Low grade epithelium in LAMN
LAMN with extra-appendiceal mucin
Extra-appendiceal mucin with serosal reaction
Cellular extra-appendiceal mucin
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Noncompressible appendix with thickened lamina propria
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Intussuscepted appendix on colonoscopy
Contributed by Mahzad Azimpouran, M.D. and Danielle Hutchings, M.D.
Dilated appendix
Grossly unremarkable appendix
Thickened mucosal layer
Contributed by Mahzad Azimpouran, M.D. and Danielle Hutchings, M.D.
Cross section
Lymphoid hyperplasia of tip
Lymphoid aggregates expanding lamina propria
Prominent lymphoid follicles
Reactive lymphoid follicles
Reactive lymphoid hyperplasia
Grading appendiceal mucinous neoplasms
| Tumor grade | In the appendiceal primary tumor | In the peritoneal metastasis |
| 1 | Low grade cytology with a pushing margin (low grade appendiceal mucinous neoplasm) | Hypocellular mucinous deposits Neoplastic epithelial elements have low grade cytology No infiltrative type invasion |
| 2 | High grade cytology with a pushing margin (high grade appendiceal mucinous neoplasm) Invasive mucinous adenocarcinoma without a signet ring cell component | Hypercellular mucin deposits as judged at 20x magnification
High grade cytological features Infiltrative type invasion characterized by jagged or angulated glands in a desmoplastic stroma or a small mucin pool pattern with numerous mucin pools containing clusters of tumor cells |
| 3 | Signet ring cell adenocarcinoma with numerous signet ring cells in mucin pools or infiltrating tissue | Mucinous tumor deposits with signet ring cells |
- Note: several different neoplasms are covered by this table
- LAMN should be grade 1 (primary)
- HAMN should be grade 2 (primary)
- Mucinous adenocarcinoma should be grade 2 (primary)
- Signet ring cell carcinoma should be grade 3 (primary)
- Pseudomyxoma from LAMN or HAMN can be any grade (peritoneal)
- Pseudomyxoma from adenocarcinoma can be any grade (peritoneal) but is almost always grade 2 or 3
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Hypodense ovoid structure
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Distended appendix with intact wall
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Mucin and globules
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Alcian blue staining of globules
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Ultrasound and CT scan
Contributed by Robert Grefka, P.A. (ASCP)CM
Appendiceal NET involving mesentery
Contributed by Kwun Wah Wen, M.D., Ph.D. and @jgwBMS on Twitter
NET in nests
Nests and trabeculae
Monomorphic, low grade
Salt and pepper chromatin
Well differentiated neuroendocrine tumor
Negative mucicarmine
Diffusely strong synaptophysin
Diffusely strong chromogranin A
Low Ki67 index
Well differentiated neuroendocrine tumor
Neuroendocrine tumor, appendix - histopathology
Contributed by Lukas Streich, M.D.
Periappendicitis
Contributed by Maryam Kherad Pezhouh, M.D., M.Sc.
Absent luminal inflammation
Serosal inflammation
Inflammation and edema
Neutrophils at serosa
Sparing of muscularis
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Morphological patterns of PMP
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Ascitic fluid
Mucinous ascites
Cytoreductive surgery
Cytoreductive surgery with HIPEC
Contributed by Alex Placek, M.D.
Omental nodules
Contributed by Alex Placek, M.D.
Low cellularity
Low grade cytology
Increased cellularity
Invasion with desmoplasia
Signet ring cells
Degenerated mucinous cells
Contributed by Raul S. Gonzalez, M.D.
Small polyp
Ill defined polyp
Contributed by Michael Feely, D.O.
Serrated polyp of appendix
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Double contrast barium enema
Abdominal CT scan
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Grossly visible appendiceal adenoma
Contributed by Raul S. Gonzalez, M.D.
Tubular glands with elongated, hyperchromatic nuclei and crowded glands
Crowded tubular and villous glands with elongated hyperchromatic nuclei
Mucinous appearance
Adenocarcinoma arising in adenoma
Greenson: 2019
IARC: 2019
Montgomery: 2024
Odze: 2022
Srivastava: 2023
Voltaggio: 2024
Yantiss: 2021
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