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).

Benign disease

Anal wart

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.[5]

Hemorrhoids

Main article: Hemorrhoid

Anal neoplasia

Immunosuppressed individuals and homosexuals have a higher risk of anal intraepithelial neoplasia (AIN) and anal cancer.[6][7]

Anal intraepithelial neoplasia

  • Abbreviated AIN.

General

Grading

AIN is graded much like cervical intraepithelial neoplasia:

  • High-grade anal intraepithelial neoplasia (HGAIN).
  • Low-grade anal intraepithelial neoplasia (LGAIN).

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ANAL CANAL, RIGHT UPPER QUADRANT, BIOPSY:
- LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION (CONDYLOMA ACUMINATUM-LIKE).

ANAL CANAL, LEFT UPPER QUADRANT, BIOPSY:
- LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION.
- RECTAL MUCOSA WITHIN NORMAL LIMITS.

SKIN LESION, PERIANAL, BIOPSY: 
- ANAL INTRAEPITHELIAL NEOPLASIA 3 (SEVERE DYSPLASIA), WARTY-TYPE.
- MARGIN POSITIVE FOR ANAL INTRAEPITHELIAL NEOPLASIA 3.

Micro

There is dysplastic squamous epithelium with coarse chromatin, nuclear hyperchromasia, nuclear enlargement, irregular nuclear membranes, and an increase nuclear-to-cytoplasmic ratio. Mitotic activity is abundant. Several atypical mitoses are identified.

The dysplastic squamous epithelium shows minimal maturation toward the surface (AIN 3). A sizable portion of the lesion show some maturation to the surface (AIN 2).

Inflammation at the dermal-epidermal interface is minimal and the dermal-epidermal interface is well-demarcated. Focal ulceration is present.

The margin of the biopsy has severely dysplastic epithelium (AIN 3).

Anal cancer

Anal squamous cell carcinoma

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

General

  • Most common form of anal cancer.

Risk factors:[8]

  • Men who have sex with men.
  • Immunosuppressed.
  • HIV infection.

Microscopic

Features:

DDx:

IHC

  • p16 +ve.[9]
  • CDX2 -ve/+ve.
    • May be useful to differentiate from vulva and penis.[9]

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RECTUM, DISTAL, BIOPSY:
- INVASIVE SQUAMOUS CELL CARCINOMA.

Anal gland adenocarcinoma

  • Abbreviation AGA.
  • AKA anal adenocarcinoma.

General

  • Rare.

Risk factors:[10]

Microscopic

Features:[11]

  • 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:[11]

  • CK7 +ve (5 of 5[12]).
  • p16 -ve (5 of 5[12]).
  • CK20 -ve.
  • CDX2 -ve.
  • p63 -ve.
  • PSA -ve.

See also

References

  1. ↑ 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.
  2. ↑ 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.
  3. ↑ Burri, E.; Vavricka, SR. (Jul 2013). "[Perianal Crohn's disease].". Ther Umsch 70 (7): 417-28. doi:10.1024/0040-5930/a000427. PMID 23798025.
  4. ↑ 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.
  5. ↑ 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.
  6. ↑ 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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2860554/.
  7. ↑ 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.
  8. ↑ Kutlubay, Z.; Engin, B.; Zara, T.; Tüzün, Y.. "Anogenital malignancies and premalignancies: Facts and controversies.". Clin Dermatol 31 (4): 362-73. doi:10.1016/j.clindermatol.2013.01.003. PMID 23806153.
  9. ↑ 9.0 9.1 Gunia, S.; Koch, S.; May, M. (Feb 2013). "Is CDX2 immunostaining useful for delineating anorectal from penile/vulvar squamous cancer in the setting of squamous cell carcinoma with clinically unknown primary site presenting with histologically confirmed inguinal lymph node metastasis?". J Clin Pathol 66 (2): 109-12. doi:10.1136/jclinpath-2012-201138. PMID 23105122.
  10. ↑ Tarazi, R.; Nelson, RL.. "Anal adenocarcinoma: a comprehensive review.". Semin Surg Oncol 10 (3): 235-40. PMID 8085101.
  11. ↑ 11.0 11.1 11.2 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.
  12. ↑ 12.0 12.1 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.
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