| Abstract|| |
Adenocarcinoma of the anal canal accounts for about 20% of all anal canal cancers. It is subclassified into two types. (1) Colorectal type, which arises from the mucosa above dentate line and (2) extramucosal type, which includes adenocarcinoma arising in anorectal fistulae and adenocarcinoma arising from anal glands. Anal gland adenocarcinomas are extremely rare. In this article, we present two cases of anal adenocarcinoma, one colorectal type, and other anal gland carcinoma along with review of literature.
Keywords: Anal adenocarcinoma, anal gland, colorectal, perianal
|How to cite this article:|
Kulkarni MP, Momin YA, Pandav AB, Sulhyan KR. Adenocarcinoma of the anal canal: A report of two cases with review of literature. Indian J Pathol Microbiol 2016;59:404-6
|How to cite this URL:|
Kulkarni MP, Momin YA, Pandav AB, Sulhyan KR. Adenocarcinoma of the anal canal: A report of two cases with review of literature. Indian J Pathol Microbiol [serial online] 2016 [cited 2019 Aug 24];59:404-6. Available from: http://www.ijpmonline.org/text.asp?2016/59/3/404/188139
| Introduction|| |
Around 75% of tumors of anal canal are squamous cell carcinomas while over 20% are adenocarcinomas. Adenocarcinoma of anal canal is an adenocarcinoma arising in the epithelium of the anal canal including the mucosal surface, the anal glands, and the lining of fistulous tracts. The risk factors for the development of anal adenocarcinoma include smoking, HIV infection, homosexuality, anal Crohn's disease, and chronic fistula-in-ano., They could be colorectal type arising in anal mucosa above dentate line or extramucosal (perianal) adenocarcinoma. The extramucosal adenocarcinoma is a rare entity characterized by primarily extramucosal or intramural growth without a luminal component. The tumor invades the submucosa widely, and since the overlying mucosa is uninvolved, it can be mistaken for metastatic gastrointestinal carcinoma. These tumors may be associated with a preexisting anal fistula or may arise from anal glands which are mucus producing branched tubular structures having ducts opening at the dentate line. We report two cases of anal adenocarcinoma, one colorectal type, and the other anal gland carcinoma.
| Case Reports|| |
A 57-year-old male presented with bleeding per rectum off and on and pain during defecation of 6 months duration. He also complained of groin swelling since 1 month. On per rectal examination, concentric growth was felt in the anal canal measuring 5 cm in length. There was no fistula. Computerized tomography (CT) scan showed a large heterogeneously enhancing mass lesion in the anal canal measuring 6 cm × 4 cm × 2.2 cm extending into bilateral ischiorectal and ischioanal fossae. The rectum did not show any tumor. Bilateral internal iliac lymph nodes were enlarged and showed punctate calcification. Bilateral inguinal lymph nodes were enlarged, largest measuring 3 cm × 2 cm and were hard in consistency. Fine needle aspiration cytology (FNAC) of the lymph nodes was positive for malignant cells and revealed metastatic mucin secreting adenocarcinoma. Patient was HIV nonreactive. His hemogram, liver, and kidney function tests were within normal limits.
Incisional biopsy from the growth revealed a tumor composed predominantly of lakes of mucin with few glands lined by columnar cells having vesicular nuclei, prominent nucleoli, and scant eosinophilic cytoplasm. The overlying anal mucosa was ulcerated but nonneoplastic [Figure 1]a. A diagnosis of mucinous adenocarcinoma of anal canal was rendered. On immunohistochemistry (IHC), cytokeratin 7 (CK7) was negative, whereas CK20 and CDX2 were positive, confirming the colorectal phenotype [Figure 1]b, [Figure 1]c, [Figure 1]d. Patient was advised palliative chemo and radiotherapy as the tumor was not resectable.
|Figure 1: (a) Section of the tumor showing lakes of mucin and neoplastic glands beneath the nonneoplastic mucosa (H and E, ×40). (b) CK7 negative. (c) CK20 positive. (d) CDX2 positive|
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A 75-year-old female presented with progressively increasing difficulty in defecation of 4 months duration. She also complained of bleeding per rectum. Local examination showed an ulceroproliferative growth over the right side of the anus measuring 4 cm × 2.5 cm per rectal examination was painful and revealed circumferential wall thickening 6 cm in length. There was no fistula. CT scan confirmed a heterogeneously enhancing concentric wall thickening of the anal canal measuring 5.5 cm × 7 cm × 4.8 cm. The rectum did not show any tumor. The growth also involved the adjacent ischiorectal and ischioanal fossae. Extensive fat streaking suggestive of lymphatic invasion and enlarged calcified lymph nodes were evident in the ischiorectal and ischioanal fossae. She was nonreactive for HIV. Her hemogram revealed anemia with hemoglobin of 10 gm%. Liver function tests and kidney function tests were within normal limits.
Biopsy from the growth showed a tumor composed of cuboidal to columnar cells with pleomorphic vesicular nuclei and moderate amount of eosinophilic cytoplasm arranged in a tubular and acinar pattern. Scant intraluminal mucin was noted. The tumor was seen originating from the adjacent anal glands. The overlying stratified squamous mucosa was unremarkable [Figure 2]. Diagnosis of anal gland adenocarcinoma was offered. As the biopsy was very tiny, no tissue was left for IHC. Patient was advised palliative chemotherapy followed by radiation. However, she refused to take treatment and was discharged against medical advice. Hence, repeat biopsy could not be done.
|Figure 2: The tumor is composed of acini and tubules in continuity with benign anal glands (H and E, ×40)|
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| Discussion|| |
The anal canal is histologically divided into three parts on the basis of its lining epithelium: Colorectal zone lined by colorectal type glandular mucosa proximally, anal transition zone lined by an epithelium having varying appearances in the middle, and squamous epithelium-lined distal portion. Hence, despite its short length, the anal canal produces a variety of tumor types reflecting its complex anatomic and histological structure. Most adenocarcinomas in the anal canal are rectal carcinomas that have grown distally or arise from the rectal mucosa above the dentate line. They do not differ morphologically from rectal carcinomas and are characterized by being primarily luminal. The most significant clinical implication of distinguishing the anal canal origin of these tumors relates to its pattern of local spread which reflects its dual lymphatic drainage. These tumors carry a high risk of metastasis to the inguinal and femoral nodes than rectum-based adenocarcinomas. In our Case 1, the patient had presented with bilateral inguinal lymphadenopathy along with pain during defecation and bleeding per rectum. FNAC of both lymph nodes revealed metastatic mucin secreting adenocarcinoma, morphologically similar to the tumor proper. The tumor mucin was periodic acid-Schiff positive. IHC showed negative CK7 and positive CK20 as well as CDX2, confirming the colorectal phenotype.,
The other type of adenocarcinoma of the anal canal, the extramucosal (perianal) carcinoma is a rare entity. A minimum criterion for diagnosis is an overlying nonneoplastic mucosa, which may be ulcerated. It includes two groups depending on its association with either fistulae or anal glands. Carcinoma associated with chronic fistulae-in-ano was first described by Rosser in 1934. The tumor usually presents as a large, painful buttock mass. A long history of fistulae-in-ano and multiple perirectal abscesses is characteristic. The exact cell of origin is difficult to determine. These are usually of the mucinous type. However, perianal mucinous adenocarcinomas arising from anal glands without fistula formation have also been reported.,,
Adenocarcinomas arising from anal glands are still rare. The most recent WHO definition of anal gland carcinoma stresses the morphology and histogenesis. It also states that only a few reported cases have shown evidence for an origin in anal glands by continuity between anal gland epithelium and tumor. Our second case fulfills these criteria. The tumor was composed of small acini and tubules with scant mucin production, and continuity was clearly evident between the tumor and the anal gland epithelium. Furthermore, the overlying squamous mucosa was ulcerated but nonneoplastic. In a significant proportion of cases, however, a direct relation of the tumor to anal glands cannot be established because of obliteration of the point of origin, effacement of the primary tumor site, associated inflammatory changes, or the vagaries of sampling. Hence, Hobbs et al. have proposed a definition of anal gland carcinoma as a tumor composed of haphazardly dispersed small glands with scant mucin production invading the wall of anorectal area without an intraluminal component, the glands being CK7 positive. This definition does not require continuity of the invasive tumor with benign anal glands. According to Hobbs et al., a primary intramural anal canal tumor composed of small dispersed gland could be considered as anal gland carcinoma even without examination of CK expression. Our second case fulfills these criteria, hence is anal gland adenocarcinoma. Unfortunately, we could not do IHC in this case as the biopsy was very tiny.
Literature review on IHC of anal gland carcinoma shows CK7+ and CK20− phenotype. In addition, there is a loss of p63 and CK5/6 expression along with a uniform negativity for CDX2, the intestinal differentiation marker. The latter can be helpful for differentiating anal gland carcinoma from rectal adenocarcinomas which are CDX2 positive.,, However, focal positivity for CDX2 in anal gland carcinoma has also been reported.
| Conclusion|| |
We have presented two cases of anal adenocarcinoma. The perianal mucinous adenocarcinomas arising from anal canal are morphologically similar to rectum-based mucinous carcinomas but differ prognostically as the former have increased risk of metastasis to inguinal lymph nodes. IHC plays a pivotal role in differentiating these two. Anal gland adenocarcinomas are very rare and can be reasonably diagnosed when the tumor is primary in the anal canal, centered within the wall of anorectal area, without a preexisting fistula and without surface mucosal involvement irrespective of the extent of mucin production. Review of literature showed only a few case reports. Hence, the exact incidence is not known. Study of more cases is required for uniformity in diagnosis and development of treatment protocols.
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Dr. Amitkumar Bapuso Pandav
Department of Pathology, Government Medical College, Miraj - 416 410, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]