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

  • Common.

Microscopic

Features:

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

DDx:

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PERIANAL MASS, EXCISION: 
- PERIANAL ABSCESS. 
- REACTIVE SQUAMOUS EPITHELIUM WITH PARAKERTOSIS AND ULCERATION. 
- ABUNDANT COCCI ORGANISMS IN CLUSTERS. 
- NEGATIVE FOR MALIGNANCY.

Hidradenoma papilliferum

See Hidradenoma papilliferum.
  • Can be perianal.[1]

Hemorrhoids

General

  • Benign.

Clinical features:[2]

  • Bright red blood per rectum (BRBPR).
  • Pain.
  • Itching.
  • Prolapse.

Gross

Features:[3]

  • Grey mucosa.
  • Pale or purple stroma.

Microscopic

Features:[3]

  • Polypoid lesion - epithelium on three sides:
    • Large dilated veins and thick-walled vessels +/- fibrin thrombi - key feature.
    • Edema.
    • Squamous epithelium +/- keratinization or columnar epithelium.

DDx:

Image:

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ANAL LESION:
- HEMORRHOID.

HEMORRHOIDS, EXCISION: 
- HEMORRHOIDS.

Micro

The sections show rectal and anal mucosa, and a submucosa with prominent blood vessels in a fibrotic stroma. The rectal mucosa has focal reactive nuclear changes and evidence of prior erosions. The anal mucosa is unremarkable.

Anal neoplasia

Immunosuppressed individuals and homosexuals have a higher risk of anal intraepithelial neoplasia (AIN) and anal cancer.[4][5]

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:[6]

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

Microscopic

Features:

DDx:

IHC

  • p16 +ve.[7]
  • CDX2 -ve/+ve.
    • May be useful to differentiate from vulva and penis.[7]

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

Anal gland adenocarcinoma

  • Abbreviation AGA.
  • AKA anal adenocarcinoma.

General

  • Rare.

Risk factors:[8]

Microscopic

Features:[9]

  • 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:[9]

  • CK7 +ve (5 of 5[10]).
  • p16 -ve (5 of 5[10]).
  • CK20 -ve.
  • CDX2 -ve.
  • p63 -ve.
  • PSA -ve.

See also

References

  1. ↑ 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.
  2. ↑ Cazemier, M.; Felt-Bersma, RJ.; Cuesta, MA.; Mulder, CJ. (Jan 2007). "Elastic band ligation of hemorrhoids: flexible gastroscope or rigid proctoscope?". World J Gastroenterol 13 (4): 585-7. PMID 17278225.
  3. ↑ 3.0 3.1 Iacobuzio-Donahue, Christine A.; Montgomery, Elizabeth A. (2005). Gastrointestinal and Liver Pathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 401. ISBN 978-0443066573.
  4. ↑ 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/.
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ 7.0 7.1 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.
  8. ↑ Tarazi, R.; Nelson, RL.. "Anal adenocarcinoma: a comprehensive review.". Semin Surg Oncol 10 (3): 235-40. PMID 8085101.
  9. ↑ 9.0 9.1 9.2 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.
  10. ↑ 10.0 10.1 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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