CytoLyt fixation impedes insulinoma-associated protein 1 (INSM1) immunoreactivity compared to formalin fixation.

INTRODUCTION: Insulinoma-associated protein 1 (INSM1) is an immunohistochemical marker commonly used to confirm cytomorphological concordant neuroendocrine tumors/carcinomas (NETs/NECs), demonstrating high utility in small samples. Previous reports have suggested comparable INSM1 staining in CytoLyt-fixed cell blocks and formalin-fixed surgical pathology specimens. This study aimed to assess INSM1 immunoreactivity using both fixation methods and investigate potential factors contributing to its variable expression. MATERIALS AND METHODS: A retrospective query was performed (03/31/21-05/31/22) for NET/NEC cases that had both formalin- and CytoLyt-fixed cell blocks. We collected clinical data and reporting of immunostains for each case. INSM1 staining was evaluated in both fixation methods, and reported as positive, negative, or equivocal. Equivocal INSM1 staining was further scored as a percentage of 1%-100% and intensity of weak (faint staining), moderate (darker staining), and strong (dense staining). RESULTS: Our search identified 20 cases from diverse body sites, including mediastinal lymph nodes (40%), pancreas (35%), lung (20%), and porta hepatis lymph nodes (5%). All cases exhibited a widespread positivity (over 90%) in formalin-fixed cell blocks. In contrast, CytoLyt fixed cells showed a negative stain in 65% of cases and 30% exhibited an equivocal positivity. CONCLUSIONS: While INSM1 is previously reported as a sensitive (75%-100%) and specific (82.7%-100%) marker for NET/NECs, our study found a reduced immunohistochemical staining in CytoLyt-fixed cell blocks. Consequently, false negative INSM1 immunohistochemical results in CytoLyt-fixed cell block material may pose a pitfall in the diagnosis of NET/NEC.

Significance of concurrent HPV testing with unsatisfactory Papanicolaou test for prediction of follow-up HPV, Papanicolaou test, and biopsy results.

OBJECTIVES: Approximately 1% to 2% of routine cytologic specimens collected for Papanicolaou testing are unsatisfactory for evaluation. The American Society for Colposcopy and Cervical Pathology 2019 guidelines recommend repeat testing within 2 to 4 months of an unsatisfactory Papanicolaou test (UPT) result. METHODS: We evaluated the utility of follow-up Papanicolaou testing, human papillomavirus (HPV) testing, and biopsy in 258 cases of UPTs. RESULTS: High-risk HPV testing was positive in 17.4% (n = 45) and negative in 82.6% (n = 213) of cases at the time of initial UPT; 8.1% (n = 21) of cases had discordant HPV test results. Similarly, 3.8% (n = 8) of initially HPV-negative cases were reported to be HPV-positive on follow-up; 28.9% (n = 13) of initially HPV-positive cases were reported to be HPV negative on follow-up. In total, 27.1% (n = 70) of cases underwent biopsy. Biopsies with significant findings were present in 40% (n = 12) of HPV-positive cases and 7.5% (n = 3) of HPV-negative cases. Low-grade squamous intraepithelial lesion (LSIL) (low-grade cervical intraepithelial neoplasia [CIN-1]) was the most significant finding in all 3 HPV-negative biopsies; 58.3% (n = 7) of HPV-positive biopsies showed LSIL (CIN-1), 13.3% (n = 4) showed HSIL (high-grade CIN), and 3.3% (n = 1) showed invasive carcinoma. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of concurrent HPV testing at the time of UPT for predicting follow-up HPV test result within 1 year of initial UPT are 80.0%, 94.0%, 71.1%, and 96.2%, respectively. The sensitivity, specificity, PPV, and NPV of initial HPV test results for predicting follow-up Papanicolaou test results are 67.7%, 89.7%, 48.8%, and 95.0%, respectively. RESULTS: Concurrent HPV testing in the setting of UPT can be a sensitive tool for predicting follow-up HPV status and significant findings of squamous intraepithelial lesions on follow-up Papanicolaou tests and biopsy.

Cytological features of choricarcinoma in a Pap smear: A case report and literature review.

Choriocarcinoma is an aggressive malignant trophoblastic tumor that mostly occurs during reproductive years. Cytological features of choriocarcinoma in gynecologic Pap smears have not been described. Herein, we report a case of choriocarcinoma in a Pap smear of a patient who had a history of choriocarcinoma with metastatic disease.