An unusual liver tumor with challenging morphologic features and immunophenotype: A case report of metastatic HPV-driven basaloid anal squamous cell carcinoma

Abstract

Abstract Introduction/Objective Basaloid squamous cell carcinoma (BSCC), a rare subtype of squamous cell carcinoma, occurs most commonly in esophagus, lungs, and head and neck. Anal BSCC is extremely rare and has a 10-20% rate of metastasis. High-risk HPV (HR-HPV) is the main causative agent. BSCC occurrence in an atypical site without a known primary tumor, and with atypical immunoprofile can be a diagnostic challenge. Methods/Case Report We report an 83-year-old female with history of breast carcinoma who presented for worsening chest pain. Imaging studies showed pulmonary nodules, 1.8 cm hepatic mass, and pelvic nodules. Liver biopsy showed infiltrating nests of carcinoma with solid and cribriform patterns and luminal necrosis. Some tumor nests had basaloid features with peripheral palisading. Tumor was positive for CK7 and pankeratin; and negative for ER, SOX10, GATA3, GCDFP-15 (Breast markers), CDX2 (GI marker), P63 and P40 (squamous markers), INSM1, Synaptophysin (Neuroendocrine) and TTF1 (lung adenocarcinoma). There was microfocal staining with CK20 and SATB2. Tumor morphology and immunophenotype were not entirely specific to the site of origin. Further search into patient’s medical history showed a recent anal mucosal biopsy revealing a high-grade squamous epithelial lesion with diffuse P16 reactivity. The slides for the anal lesion were reviewed and showed morphologic features similar to the liver biopsy. Additional studies showed both tumors were positive for HR-HPV ISH, P16 (diffuse), and CK5/6 (patchy); and negative for P63. The morphologic features and immunoprofile were supportive of metastasis from HPV-driven BSCC of anus. Subsequent PET Scan revealed a rectal/anal mass. Results (if a Case Study enter NA) NA Conclusion For tumors with unusual morphology and immunophenotype, complete medical history review, and communication with clinician are important tools in achieving correct diagnosis. HR-HPV ISH is a new tool that can be very useful in reaching correct diagnosis in metastatic anogenital or oropharyngeal squamous carcinomas with basaloid features.