| Abstract|| |
Cloacogenic carcinoma also known as basaloid squamous cell carcinoma is a rare anorectal tumor presenting with varied histomorphology. In this case report, we describe a case of 58-year-old man presenting with bleeding per rectum and pain. A polypoidal tumor was noted in anal canal which on microscopy was diagnosed to be cloacogenic carcinoma with transitional carcinoma-like, basaloid and mucinous patterns. An unusual finding in the present case was the presence of signet ring cells in the mucinous areas. A thorough knowledge of the wide histomorphological spectrum of the tumor and a limited IHC panel are crucial for the diagnosis. Here, we also present a review of literature and describe in detail the origin and histopathological features of the tumor.
Keywords: Anal canal, basaloid carcinoma, basaloid squamous cell carcinoma, cloacogenic carcinoma, transitional cloacogenic carcinoma
|How to cite this article:|
Gurumurthy RY, Shankar N S, Mohan Raj C S, Sriram N. HPV related cloacogenic carcinoma of the anal canal with divergent histomorphology. Indian J Pathol Microbiol 2019;62:464-6
|How to cite this URL:|
Gurumurthy RY, Shankar N S, Mohan Raj C S, Sriram N. HPV related cloacogenic carcinoma of the anal canal with divergent histomorphology. Indian J Pathol Microbiol [serial online] 2019 [cited 2020 Dec 1];62:464-6. Available from: https://www.ijpmonline.org/text.asp?2019/62/3/464/263474
| Introduction|| |
Cloacogenic carcinoma, also known as basaloid squamous cell carcinoma is a rare tumor of the anorectal region arising from the persistent remnant of cloacal membrane. The heterogeneity of the histologic patterns present normally in the epithelium of this region results in neoplasms with varied histological patterns. Due to its rarity, there is a paucity of data on the histomorphologic patterns of this tumor, which may result in its misdiagnosis.
| Case Report|| |
A 58-year-old man presented with the complaints of increasingly painful bowel movements and bleeding per rectum. Clinical and endoscopic examination revealed a large, polypoidal mass in the anal canal. A diagnosis of anal canal malignancy was made and multiple biopsies were taken. On microscopic examination of the tumor, there were areas of transitional carcinoma-like pattern, basaloid pattern, and mucinous pattern with signet ring cells as seen in [Figure 1]. On immunohistochemical studies, the tumor cells were immunopositive for P16, CK5&6, P63 and showed focal reactivity for carcinoembryonic antigen (CEA) as seen in [Figure 2]. The tumor cells were immunonegative for CDX2. The report was signed out as cloacogenic/basaloid carcinoma of the anal canal and the patient subsequently underwent abdomino-perineal resection with standard chemoradiation.
|Figure 1: (a) Photomicrograph showing tumor arising from the mucosa (H and E, ×10). (b) Scanner view of the tumor showing tumor cells arranged in papillary pattern, ribbons, clusters, and nests with central eosinophilic necrosis (H and E, ×4). (c) Photomicrograph showing transitional carcinoma like areas (H and E, ×40). (d) Photomicrograph showing basaloid area (H and E, ×10). (e and f) Photomicrograph showing mucinous area with clear cells and signet ring cells (H and E, ×40)|
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|Figure 2: (a) Tumor cells showing immunopositivity for P16 (×10). (b) Tumor cells showing immunopositivity for CK 5 and 6 (×40). (c) Tumor cells showing immunopositivity for P63 (×10). (d) Tumor cells showing faint, focal reactivity for CEA (×10). (e) Tumor cells showing faint, focal reactivity for CEA (×40). (f) Tumor cells showing immunonegativity for CDX2 (×10)|
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| Discussion|| |
Cloacogenic carcinoma accounts for 2%–3.2% of all anorectal neoplasms. The tumor has been etiologically linked to human papillomavirus (HPV). IHC study with P16 was strongly positive in the present case, suggesting the etiological role of HPV.
Cloacogenic carcinoma arises from persistent remnant of the cloacal membrane of the embryo. The predilection of the tumor for this transitional zone reflects its inherent epithelial instability which is a feature of many junctional zones throughout the body. It is a circular zone measuring 0.6–1.2 cm at level of columns of Morgagni. Its mucosa has an appearance that is intermediate between that of non-keratinizing squamous and columnar epithelium and contain several cell types in varying proportion: basaloid, columnar, cuboidal, transitional, and squamous cells. IHC studies indicate that the tumor arises from anal transitional zone epithelium, basal layer of anal squamous epithelium or basal cells of anal glands. Ultrastructural studies suggest that poorly differentiated variants of the tumor arise from basal layer of the transitional zone epithelium.
On gross examination, cloacogenic carcinoma may present as fungating, ulcerated, excavated, polypoidal, or hemorrhoid like mass. On microscopic examination, this tumor is characterized by varied morphologic patterns between and within cases. The transitional carcinoma-like pattern is characterized by rounded nests and ribbons of uniform, ovoid-elongated, intermediate-sized tumor cells with faintly eosinophilic cytoplasm, oval open nuclei, and variably prominent nucleoli. The basaloid areas show infiltrating tumor nests composed of basaloid cells with scanty basophilic cytoplasm and pleomorphic, hyperchromatic nuclei showing peripheral palisading. The adenoid cystic carcinoma-like areas demonstrate nodules of neoplastic cells which are hyperchromatic, small and encircled by hyaline basement membrane like material. The mucoepidermoid carcinoma-like area is characterized by small cystic foci lined by mucin producing cells. The mucinous microcystic areas show neoplastic cells with clear cytoplasm, which are focally discohesive and form microcystic spaces. Squamoid areas with individual cell keratinization can be seen in some tumors, although keratin pearls and prickle cells are uncommon. The highly anaplastic variants mimic oat cell carcinoma of the lung. Present case showed transitional carcinoma-like, basaloid, and mucinous areas. An unusual microscopic finding in the present case was the presence of signet ring cells in the mucinous areas. The clinical significance and associated pathologic variables of this rare morphologic finding are uncertain at this point.
On gross examination, the tumor mimics adenocarcinoma. On microscopy, differential diagnosis for transitional carcinoma-like pattern of cloacogenic carcinoma include, metastatic urinary transitional cell carcinoma and primary neuroendocrine tumor. Basaloid areas of the tumor must be differentiated from basal cell carcinoma. The adenoid cystic carcinoma-like pattern of the tumor may be confused with metastatic salivary adenoid cystic carcinoma and basal cell adenocarcinoma. The mucoepidermoid carcinoma-like pattern of the tumor resembles metastatic salivary mucoepidermoid carcinoma. The anaplastic variants sometimes mimic oat cell carcinoma of the lung. Thus detailed histomorphological examination along with IHC studies is required for accurate diagnosis. Tumor cells in the present case demonstrated combined immunopositivity to CK5&6, and P63, which is suggestive of basaloid carcinoma. In the present case, the mucinous areas showed signet ring cells resembling signet ring cell adenocarcinoma. However, the tumor cells were immunonegative for CDX2 and showed only faint, focal reactivity for CEA, thus ruling out the possibility of signet ring cell adenocarcinoma.
The reports on prognosis of this tumor are not consistent. It is said to depend on factors like age, tumor size, differentiation of tumor cells, fibroblastic activity within the tumor, inflammatory reaction in the surrounding tissue, depth of invasion, lymphatic, and vascular metastasis.
| Conclusion|| |
Cloacogenic carcinoma is a rare tumor which presents with varied histomorphological features. Reduced awareness of the practicing pathologists about the histopathological spectrum of the tumor may dampen the diagnostic acumen. Careful histopathological examination with awareness of different morphologic findings, consideration of alternative differential diagnosis, and a limited immunohistochemical panel are essential for the accurate diagnosis, which in turn determines the further management and prognosis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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Radhika Yajaman Gurumurthy
#1116, 5th Cross, 1503, Srirampet, Vinoba Road, Mysore - 570 001, Karnataka
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]