In-depth analysis of immunohistochemistry concordance in biopsy-resection pairs of bronchial carcinoids.

Primary diagnosis of bronchial carcinoids (BC) is always made on biopsies and additional immunohistochemistry (IHC) is often necessary. In the present study we investigated the concordance of common diagnostic (synaptophysin, chromogranin, CD56 and INSM-1) and potential prognostic (OTP, CD44, Rb and p16) IHC markers between the preoperative biopsies and resections of in total 64 BCs, 26 typical (41 %) and 38 atypical (59 %) carcinoid tumors. Synaptophysin and chromogranin had 100 % concordance in all resected carcinoids and paired diagnostic biopsies. Synaptophysin was not affected by variable expression in biopsies compared to chromogranin, CD56 and INSM-1. Notably, INSM-1 IHC was false negative in 8 % of biopsies. Of the novel and potential prognostic markers, only CD44 showed 100 % concordance between biopsies and resections, while OTP showed two (4 %) false negative results in paired biopsies. While Rb IHC was false negative in 8 % of biopsies, no strong and diffuse pattern of p16 expression was observed. In this study, most false negative IHC results (85 %, 22/26) were observed in small flexible biopsies. Taken together, our data suggest excellent concordance of synaptophysin and CD44 on the preoperative biopsy samples, while other neuroendocrine markers, Rb and OTP should be interpreted with caution, especially in small biopsies.

A Multimodal Biomarker Predicts Dissemination of Bronchial Carcinoid.

Background: Curatively treated bronchial carcinoid tumors have a relatively low metastatic potential. Gradation into typical (TC) and atypical carcinoid (AC) is limited in terms of prognostic value, resulting in yearly follow-up of all patients. We examined the additional prognostic value of novel immunohistochemical (IHC) markers to current gradation of carcinoids. Methods: A retrospective single-institution cohort study was performed on 171 patients with pathologically diagnosed bronchial carcinoid (median follow-up: 66 months). The risk of developing distant metastases based on histopathological characteristics (Ki-67, p16, Rb, OTP, CD44, and tumor diameter) was evaluated using multivariate regression analysis and the Kaplan−Meier method. Results: Of 171 patients, seven (4%) had disseminated disease at presentation, and 164 (96%) received curative-intent treatment with either endobronchial treatment (EBT) (n = 61, 36%) or surgery (n = 103, 60%). Among the 164 patients, 13 developed metastases at follow-up of 81 months (IQR 45−162). Univariate analysis showed that Ki-67, mitotic index, OTP, CD44, and tumor diameter were associated with development of distant metastases. Multivariate analysis showed that mitotic count, Ki-67, and OTP were independent risk factors for development of distant metastases. Using a 5% cutoff for Ki-67, Kaplan−Meier analysis showed that the risk of distant metastasis development was significantly associated with the number of risk predictors (AC, Ki-67 ≥ 5%, and loss of OTP or CD44) (p < 0.0001). Six out of seven patients (86%) with all three positive risk factors developed distant metastasis. Conclusions: Mitotic count, proliferation index, and OTP IHC were independent predictors of dissemination at follow-up. In addition to the widely used carcinoid classification, a comprehensive analysis of histopathological variables including Ki-67, OTP, and CD44 could assist in the determination of distant metastasis risks of bronchial carcinoids.

Diagnosis of atypical carcinoid can be made on biopsies > 4 mm2 and is accurate.

In the 2021 WHO thoracic tumors, gradation of lung carcinoids in biopsies is discouraged. We hypothesized that atypical carcinoid (AC) could be reliably diagnosed in larger preoperative biopsies. Biopsy-resection paired specimens of carcinoid patients were included, and definitive diagnosis was based on the resection specimen according to the WHO 2021 classification. A total of 64 biopsy-resection pairs (26 typical carcinoid (TC) (41%) and 38 AC (59%)) were analyzed. In 35 patients (55%), tumor classification between the biopsy and resection specimen was concordant (26 TC, 9 AC). The discordance in the remaining 29 biopsies (45%, 29 TC, 0 AC) was caused by misclassification of AC as TC. In biopsies measuring < 4 mm2, 15/15 AC (100%) were misclassified compared to 14/23 AC (61%) of biopsies ≥ 4 mm2. Categorical concordance of Ki-67 in biopsy-resection pairs at threshold of 5% was 68%. Ki-67 in the biopsy was not of additional value to discriminate between TC and AC, irrespective of the biopsy size. Atypical carcinoid is frequently missed in small bronchial biopsies (< 4 mm2). If the carcinoid classification is clinically relevant, a cumulative biopsy size of at least 4 mm2 should be considered. Our study provides strong arguments to make the diagnosis of AC in case of sufficient mitosis for AC on a biopsy and keep the diagnosis "carcinoid NOS" for carcinoids with ≤ 1 mitosis per 2 mm2. Ki-67 has a good concordance but was not discriminative for definitive diagnosis.