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Diagnosis and Discussion: Case 1158

Diagnosis

HPV ASSOCIATED ENDOCERVICAL ADENOCARCINOMA, MIXED EPITHELIAL TYPE, USUAL ENDOCERVICAL ADENOCARCINOMA AND ADENOID BASAL CARCINOMA.

Discussion

Adenocarcinoma invaded 0.5 cm into cervical stroma and measured 0.7 cm in horizontal extent.  Tumor extended to deep and endocervical resection margins.  No lymphovascular invasion was seen. The adenoid basal carcinoma is seen adjacent to usual-type invasive endocervical adenocarcinoma. Immunohistochemical stains for MOC31 highlights endocervical adenocarcinoma and glandular component of adenoid basal carcinoma while p63 is positive in basaloid component of adenoid basal carcinoma.  As expected for a HPV associated neoplasm, p16 immunohistochemical stain was diffuse strong positive in both components and both demonstrated hr- HPV signals by situ hybridization analysis.

Adenoid basal carcinoma is a rare epithelial tumor of the cervix that when present is commonly seen associated with invasive carcinomas. Epidemiologically, there is a wide age range of reported cases, from 21 to 91 years. Histologically, adenoid basal carcinomas are generally composed of small, bland, well-differentiated basaloid cells that form nests or cords.  Additional histologic features include peripheral palisading within nests, cystic change or clear cell change.  Often, adenoid basal carcinomas are discovered incidentally in the resection of other more common invasive tumors.  Most commonly, adenoid basal carcinomas occur together with squamous cell carcinoma, however cases of small cell neuroendocrine carcinoma, carcinosarcoma, and adenoid cystic carcinoma have been reported.  While in its pure form, adenoid basal carcinoma is not reported to metastasize, when mixed with other invasive components, prognosis is driven by those other tumor types.  Therefore, the WHO suggests reporting cases of adenoid basal carcinoma associated with other invasive carcinoma types as a mixed carcinoma with a description of each component and their proportion.  Immunohistochemical stains that have been reported positive in adenoid basal carcinomas include cytokeratins, p63, p16 (block positive) and high-risk HPV in situ hybridization.

Identification of adenoid basal carcinoma on Pap test is rare with the most common preceding Pap test diagnosis rendered is a high-grade squamous intraepithelial lesion.

In terms of differential diagnosis, it is important to consider adenoid basal hyperplasia, which may show similar morphology of small nests of basaloid cells attached to overlying columnar epithelium.  However, adenoid basal hyperplasia would be negative for p16 and high-risk HPV.  Another differential diagnosis that should be considered is adenoid cystic carcinoma, which occurs in a similar age group and patient population and can present in a similar fashion.  Adenoid basal and adenoid cystic carcinoma have overlapping morphologic growth pattern composed of nests of uniform “basaloid” appearing tumor cells, with high N:C ratio and focal palisading. Furthermore, both are positive for high-risk HPV.  However, adenoid cystic carcinomas generally show more sieve-like arrangement, more obvious cytologic atypia, with easily identifiable mitotic figures and stromal reaction, features which are frequently absent in adenoid basal tumor.  Ancillary tests, such as C-kit immunohistochemical stain can also be utilized in distinguishing these two tumors as C-kit is positive in adenoid cystic carcinomas but negative in adenoid basal carcinomas.

There is limited data on the cell of origin for these tumors, but some hypotheses include reserve pluripotent cervical cells or cells deriving from Skene gland, as was suggested by recent studies that demonstrate expression of NKX3.1 and prostatic acid phosphatase in adenoid basal cell carcinomas.

References

  1. Parwani AV, Smith Sehdev AE, Kurman RJ, Ronnett BM. Cervical adenoid basal tumors comprised of adenoid basal epithelioma associated with various types of invasive carcinoma: clinicopathologic features, human papillomavirus DNA detection, and P16 expression. Hum Pathol. 2005 Jan;36(1):82-90. doi: 10.1016/j.humpath.2004.08.015. PMID: 15712186.

  2. Russell MJ, Fadare O. Adenoid basal lesions of the uterine cervix: evolving terminology and clinicopathological concepts. Diagn Pathol. 2006 Aug 15;1:18. doi: 10.1186/1746-1596-1-18. PMID: 16911774; PMCID: PMC1564042.

  3. Brainard JA, Hart WR. Adenoid basal epitheliomas of the uterine cervix: a reevaluation of distinctive cervical basaloid lesions currently classified as adenoid basal carcinoma and adenoid basal hyperplasia. Am J Surg Pathol. 1998 Aug;22(8):965-75. doi: 10.1097/00000478-199808000-00006. PMID: 9706976.

  4. Talia KL, McCluggage WG. Cervical Adenoid Basal Carcinoma With High-grade Squamous Component: True Mixed Carcinoma or Colonization of Adenoid Basal Carcinoma by High-grade Squamous Intraepithelial Lesion? Am J Surg Pathol. 2024 Feb 1;48(2):238-246. doi: 10.1097/PAS.0000000000002157. Epub 2023 Nov 22. PMID: 37991261.