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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). | | The '''anus''' occasionally shows-up on the pathologists desk. It sometimes comes with the rectum and [[colon]], as an abdominoperoneal resection (APR). |
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| | =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. |
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| | Note: |
| | *Squamous epithelium 1 cm proximal to the dentate line is considered abnormal.<ref name=pmid11174313>{{Cite journal | last1 = Bujanda | first1 = L. | last2 = Iriondo | first2 = C. | last3 = Muñoz | first3 = C. | last4 = Etxezarraga | first4 = C. | last5 = Ramírez | first5 = MM. | last6 = Ramos | first6 = F. | last7 = Sánchez | first7 = A. | title = Squamous metaplasia of the rectum and sigmoid colon. | journal = Gastrointest Endosc | volume = 53 | issue = 2 | pages = 255-6 | month = Feb | year = 2001 | doi = | PMID = 11174313 }}</ref> |
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| | ==Squamous metaplasia of the anus== |
| | {{Main|Squamous metaplasia of the anus}} |
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| =Benign disease= | | =Benign disease= |
| ==Anal wart== | | ==Anal wart== |
| *See ''[[condyloma acuminatum]]''. | | *See ''[[condyloma acuminatum]]''. |
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| | ==Pilonidal cyst== |
| | :Also ''pilonidal sinus'' and ''pilonidal disease''. |
| | {{Main|Pilonidal cyst}} |
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| ==Perianal abscess== | | ==Perianal abscess== |
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| ==Anal intraepithelial neoplasia== | | ==Anal intraepithelial neoplasia== |
| *Abbreviated ''AIN''. | | *Abbreviated ''AIN''. |
| ===General===
| | {{Main|Anal intraepithelial lesions}} |
| *Precursor lesion of anal [[squamous cell carcinoma]].
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| *Usually [[HPV]] associated.
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| **May be prevented by HPV vaccine.
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| ===Grading===
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| AIN is graded much like [[cervix|cervical intraepithelial neoplasia]]:
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| *High-grade anal intraepithelial neoplasia (HGAIN).
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| *Low-grade anal intraepithelial neoplasia (LGAIN).
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| ===Sign out===
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| <pre>
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| ANAL CANAL, RIGHT UPPER QUADRANT, BIOPSY:
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| - LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION (CONDYLOMA ACUMINATUM-LIKE).
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| </pre>
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| <pre>
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| ANAL CANAL, LEFT UPPER QUADRANT, BIOPSY:
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| - LOW-GRADE SQUAMOUS INTRAEPITHELIAL LESION.
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| - RECTAL MUCOSA WITHIN NORMAL LIMITS.
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| </pre>
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| <pre>
| | Note: |
| SKIN LESION, PERIANAL, BIOPSY:
| | *The terminology changing to match the one now widely used for the [[uterine cervix]]. |
| - ANAL INTRAEPITHELIAL NEOPLASIA 3 (SEVERE DYSPLASIA), WARTY-TYPE.
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| - MARGIN POSITIVE FOR ANAL INTRAEPITHELIAL NEOPLASIA 3.
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| </pre>
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| ====Micro====
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| There is dysplastic squamous epithelium with coarse chromatin, nuclear hyperchromasia,
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| nuclear enlargement, irregular nuclear membranes, and an increase nuclear-to-cytoplasmic
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| ratio. Mitotic activity is abundant. Several atypical mitoses are identified.
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| 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).
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| Inflammation at the dermal-epidermal interface is minimal and the dermal-epidermal
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| interface is well-demarcated. Focal ulceration is present.
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| The margin of the biopsy has severely dysplastic epithelium (AIN 3).
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| =Anal cancer= | | =Anal cancer= |
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| *[[AKA]] ''anal squamous carcinoma''. | | *[[AKA]] ''anal squamous carcinoma''. |
| *[[AKA]] ''squamous cell carcinoma of the anus''. | | *[[AKA]] ''squamous cell carcinoma of the anus''. |
| ===General===
| | {{Main|Anal squamous cell carcinoma}} |
| *Most common form of anal cancer.
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| Risk factors:<ref name=pmid23806153>{{Cite journal | last1 = Kutlubay | first1 = Z. | last2 = Engin | first2 = B. | last3 = Zara | first3 = T. | last4 = Tüzün | first4 = Y. | title = Anogenital malignancies and premalignancies: Facts and controversies. | journal = Clin Dermatol | volume = 31 | issue = 4 | pages = 362-73 | month = | year = | doi = 10.1016/j.clindermatol.2013.01.003 | PMID = 23806153 }}</ref>
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| *Men who have sex with men.
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| *Immunosuppressed.
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| *[[HIV]] infection.
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| ===Microscopic===
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| Features:
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| *See ''[[squamous cell carcinoma]]''.
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| <gallery>
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| Image:Anus SquamousCellCarcinoma SCC NonKeratinizing AIA SCCIS CTR.jpg|Anus Squamous Cell Carcinoma (Non Keratinizing) - (SKB)
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| Image:Anus SquamousCellCarcinoma SCC NonKeratinizing MP CTR.jpg|Anus Squamous Cell Carcinoma (Non Keratinizing) - (SKB)
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| Image:Anus SquamousCellCarcinoma SCC NonKeratinizing MP4 CTR.jpg|Anus Squamous Cell Carcinoma (Non Keratinizing or shall we say poorly keratinizing as there are squamatized nests focally at high power) - (SKB)
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| </gallery>
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| DDx:
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| *[[Anal gland adenocarcinoma]].
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| *Poorly differentiated [[rectal adenocarcinoma]].
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| ===IHC===
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| *p16 +ve.<ref name=pmid23105122/>
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| *CDX2 -ve/+ve.
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| **May be useful to differentiate from vulva and penis.<ref name=pmid23105122>{{Cite journal | last1 = Gunia | first1 = S. | last2 = Koch | first2 = S. | last3 = May | first3 = M. | title = 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? | journal = J Clin Pathol | volume = 66 | issue = 2 | pages = 109-12 | month = Feb | year = 2013 | doi = 10.1136/jclinpath-2012-201138 | PMID = 23105122 }}</ref>
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| ===Sign out===
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| <pre>
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| RECTUM, DISTAL, BIOPSY:
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| - INVASIVE SQUAMOUS CELL CARCINOMA.
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| </pre>
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| ==Anal gland adenocarcinoma== | | ==Anal gland adenocarcinoma== |