Anus

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The anus occasionally shows-up on the pathologists desk. It sometimes comes with the rectum and colon, as an abdominoperoneal resection (APR).

Normal

  • The dentate line (also known as the pectinate line) divides the anal canal into upper two thirds and lower one third.
  • Typically, the squamocolumnar junction is just above the dentate line.

Note:

  • Squamous epithelium 1 cm proximal to the dentate line is considered abnormal.[1]

Squamous metaplasia of the anus

Benign disease

Anal wart

Pilonidal cyst

Also pilonidal sinus and pilonidal disease.

Perianal abscess

General

Microscopic

Features:

  • Abscess - (extravascular) cluster of neutrophils - key feature.
  • +/-Skin ulceration with reactive epithelium.
  • +/-Reactive stromal cells.

DDx:

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PERIANAL TISSUE ("ABSCESS"), EXCISION:
- PERIANAL ABSCESS.
- REACTIVE SQUAMOUS EPITHELIUM WITH PARAKERTOSIS AND ULCERATION.
- ABUNDANT COCCI ORGANISMS IN CLUSTERS.
- NEGATIVE FOR MALIGNANCY.
PERIANAL TISSUE ("ABSCESS"), EXCISION:
- ABSCESS.
- SKIN WITH ULCERATION AND REACTIVE CHANGES.
- NEGATIVE FOR MALIGNANCY.

Micro

The sections show skin with acanthosis, hypergranulosis, compact hyperkeratosis and focal full thickness loss of the epidermis, associated with a mixed inflammatory infiltrate. The dermis has reactive fibroblasts with moderate grey cytoplasm, nuclear enlargement and round small nucleoli. The fibroblast nuclei have regular nuclear membranes and a bland chromatin pattern. Clusters of neutrophils are present. There is no epidermal nuclear atypia. Mitotic activity is seen focally. No atypical mitotic figures are apparent. The inflammation extends to the deep aspect of the specimen.

Anal fistula

General

Microscopic

Features:

  • Squamous mucosa with acute and chronic inflammation.

DDx:

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PERIANAL TISSUE ("OPENING OF FISTULA"), EXCISION:
- PERIANAL TISSUE CONSISTING OF SCANT SQUAMOUS EPITHELIUM AND MUSCLE 
  WITH MILD INFLAMMATION.
- SMALL COLLECTION OF NEUTROPHILS.
- MILD FIBROSIS WITH FOCALLY PROMINENT DILATED BLOOD VESSELS.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY.

Hidradenoma papilliferum

See Hidradenoma papilliferum.
  • Can be perianal.[6]

Hemorrhoids

Anal neoplasia

Immunosuppressed individuals and homosexuals have a higher risk of anal intraepithelial neoplasia (AIN) and anal cancer.[7][8]

Anal intraepithelial neoplasia

  • Abbreviated AIN.

Note:

  • The terminology changing to match the one now widely used for the uterine cervix.

Anal cancer

Anal squamous cell carcinoma

  • AKA anal squamous carcinoma.
  • AKA squamous cell carcinoma of the anus.

Anal gland adenocarcinoma

  • Abbreviation AGA.
  • AKA anal adenocarcinoma.

General

  • Rare.

Risk factors:[9]

Microscopic

Features:[10]

  • Adenocarcinoma within the anal wall but not within the mucosa, i.e. extramucosal and intramural - key feature.
    • The tumour lies beneath the squamous mucosa/rectal mucosa.

DDx:

Image:

IHC

Features:[10]

  • CK7 +ve (5 of 5[11]).
  • p16 -ve (5 of 5[11]).
  • CK20 -ve.
  • CDX2 -ve.
  • p63 -ve.
  • PSA -ve.

See also

References

  1. Bujanda, L.; Iriondo, C.; Muñoz, C.; Etxezarraga, C.; Ramírez, MM.; Ramos, F.; Sánchez, A. (Feb 2001). "Squamous metaplasia of the rectum and sigmoid colon.". Gastrointest Endosc 53 (2): 255-6. PMID 11174313.
  2. Ommer, A.; Herold, A.; Berg, E.; Fürst, A.; Sailer, M.; Schiedeck, T. (Jun 2012). "German S3 guideline: anal abscess.". Int J Colorectal Dis 27 (6): 831-7. doi:10.1007/s00384-012-1430-x. PMID 22362468.
  3. Lewis, RT.; Maron, DJ. (Sep 2010). "Efficacy and complications of surgery for Crohn's disease.". Gastroenterol Hepatol (N Y) 6 (9): 587-96. PMID 21088749.
  4. Burri, E.; Vavricka, SR. (Jul 2013). "[Perianal Crohn's disease].". Ther Umsch 70 (7): 417-28. doi:10.1024/0040-5930/a000427. PMID 23798025.
  5. Benjelloun, el B.; Abkari, M.; Ousadden, A.; Ait Taleb, K. (Jul 2013). "Squamous cell carcinoma associated anal fistulas in Crohn's disease unique case report with literature review.". J Crohns Colitis 7 (6): e232-5. doi:10.1016/j.crohns.2012.09.015. PMID 23069004.
  6. Daniel, F.; Mahmoudi, A.; de Parades, V.; Fléjou, JF.; Atienza, P. (Feb 2007). "An uncommon perianal nodule: hidradenoma papilliferum.". Gastroenterol Clin Biol 31 (2): 166-8. PMID 17347625.
  7. Park IU, Palefsky JM (March 2010). "Evaluation and Management of Anal Intraepithelial Neoplasia in HIV-Negative and HIV-Positive Men Who Have Sex with Men". Curr Infect Dis Rep 12 (2): 126–133. doi:10.1007/s11908-010-0090-7. PMC 2860554. PMID 20461117. //www.ncbi.nlm.nih.gov/pmc/articles/PMC2860554/.
  8. Czoski-Murray C, Karnon J, Jones R, Smith K, Kinghorn G (November 2010). "Cost-effectiveness of screening high-risk HIV-positive men who have sex with men (MSM) and HIV-positive women for anal cancer". Health Technol Assess 14 (53): 1–131. doi:10.3310/hta14530. PMID 21083999.
  9. Tarazi, R.; Nelson, RL.. "Anal adenocarcinoma: a comprehensive review.". Semin Surg Oncol 10 (3): 235-40. PMID 8085101.
  10. 10.0 10.1 10.2 Warsch, S.; Bayraktar, UD.; Wen, BC.; Zeitouni, J.; Marchetti, F.; Rocha-Lima, CM.; Montero, AJ. (Mar 2012). "Successful treatment of anal gland adenocarcinoma with combined modality therapy.". Gastrointest Cancer Res 5 (2): 64-6. PMID 22690260.
  11. 11.0 11.1 Meriden, Z.; Montgomery, EA. (Feb 2012). "Anal duct carcinoma: a report of 5 cases.". Hum Pathol 43 (2): 216-20. doi:10.1016/j.humpath.2011.04.019. PMID 21820151.