Track: Case Reports

Abstract:

A 58-year-old female with past medical history notable for COPD, constipation, “hemorrhoids” and a 37 pack-year smoking history, presented with an increasingly painful and prolapsing perianal mass which was thought to be a large hemorrhoid. Examination revealed a 3.5 cm polypoid mass on the left-lateral anal wall, which was surgically excised. Histologic sections revealed a polypoid mass composed of nests and cords of markedly atypical basaloid cells, with brisk mitotic activity, and an unusual pagetoid component involving the overlying squamous mucosa. There was also a unique pattern of “abrupt keratinization.” Lymphovascular invasion was abundant. Immunohistochemistry demonstrated the lesional cells were positive for p40 and CK5/6, with a subset positive for CK7. P53 showed a wild-type expression pattern and p16 was largely negative. HPV in situ hybridization for both low and high-risk subtypes were negative. Next generation sequencing (DNA and RNA) identified pathologic mutations in RB1 and KMT2C with a high tumor mutational burden. Overall, the findings were consistent with a non-HPV mediated basaloid anal squamous cell carcinoma (SCC), a rare subtype. This case highlights the importance of a close examination of hemorrhoidal specimens, and also characterizes a unique histologic pattern of pagetoid spread within the overlying squamous mucosa, a finding that is not typically seen in HPV-negative SCC. Finally, this case is also unique in that it did not manifest a p53 mutation, which is very unusual for HPV-negative anal SCC.

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Joe Ferrante