The worldwide incidence of pulmonary carcinoids is increasing, but little is known about their molecular characteristics. Through machine learning and multi-omics factor analysis, we compare and contrast the genomic profiles of 116 pulmonary carcinoids (including 35 atypical), 75 large-cell neuroendocrine carcinomas (LCNEC), and 66 small-cell lung cancers. Here we report that the integrative analyses on 257 lung neuroendocrine neoplasms stratify atypical carcinoids into two prognostic groups with a 10-year overall survival of 88% and 27%, respectively. We identify therapeutically relevant molecular groups of pulmonary carcinoids, suggesting DLL3 and the immune system as candidate therapeutic targets; we confirm the value ofOTPexpression levels for the prognosis and diagnosis of these diseases, and we unveil the group of supra-carcinoids. This group comprises samples with carcinoid-like morphology yet the molecular and clinical features of the deadly LCNEC, further supporting the previously proposed molecular link between the low- and high-grade lung neuroendocrine neoplasms.

Autoimmune pancreatitis (AP) is one manifestation of a systemic, steroid-responsive disease with elevated serum IgG4 and characteristic histopathology, including increased IgG4-positive (+) plasma cells in the tissue. The histopathology of pulmonary IgG4 disease has not been well established. Six lung biopsies from patients with documented AP were studied, along with 12 additional cases showing similar pulmonary histopathology. For comparison, we examined Erdheim-Chester disease (n=3), pulmonary Sjögren syndrome (n=19), inflammatory myofibroblastic tumor (n=10), various inflammatory and interstitial lung disease (n=61), and nodal or extranodal Rosai-Dorfman disease (RD) in adults (n=8). All cases were stained for IgG4 and scored as 1, 2, and 3 as described in AP according to the following criteria: 0, 30. Five lung biopsies from AP patients showed IgG4 score of 3, and 1 had a score of 2. Consistent findings in lung biopsies of AP patients included endothelialitis of pulmonary vessels, active fibrosis, lymphangitic inflammatory infiltrates rich in plasma cells and histiocytes with or without nodule formation, and fibrinous pleuritis. Prominent lymphatic dilatation with histiocytes showing emperipolesis of lymphocytes was also seen. All 12 additional cases showing these histologic features also had the IgG4 score of 2 or 3. Among other conditions, an IgG4 score of 2 or 3 was seen in 6 of 8 RD, 4 of 10 inflammatory myofibroblastic tumors, and 8 of 61 inflammatory and interstitial lung disease, but in none of the rest. In conclusion, distinctive pulmonary histopathology was associated with increased IgG4+ cells in both AP patients and those unknown for AP status. The significance of increased IgG4+ cells in high proportion of RD cases merits further study as does overlap of RD and IgG4 disease.

Evidence suggests that metastatic colorectal carcinoma (mCRC) has a high level of intratumor heterogeneity. We carried out a quantitative assessment of tumor heterogeneity for KRAS, NRAS, BRAF and PIK3CA mutations, in order to assess potential clinical implications. Tumor samples (n = 182) from the CAPRI-GOIM trial of first-line cetuximab + FOLFIRI in KRAS exon-2 wild-type mCRC patients were assessed by next-generation sequencing that allows quantitative assessment of mutant genes. Mutant allelic frequency was normalized for the neoplastic cell content and, assuming that somatic mutations usually affect one allele, the Heterogeneity Score (HS) was calculated by multiplying by 2 the frequency of mutant alleles in neoplastic cells. Therefore, HS virtually corresponds to the fraction of neoplastic cells carrying a specific mutation. The KRAS HS ranged between 12 and 260 with mean value of 87.1 and median value of 84.4, suggesting that in most CRC, the majority of neoplastic cells carry mutant KRAS. Similar findings were observed for NRAS (HS range 35.5–146.7; mean 102.8; median 117.1). In contrast, in BRAF (HS range 17.1–120; mean 54.8; median 54.3) and PIK3CA (HS range 14.3–120; mean 59.5; median 47.3) mutant cases, only a fraction of neoplastic cells seem to carry the mutant allele. The response rate was 70% in KRAS mutant patients with an HS 33 patients (high KRAS; n = 35); median progression-free survival were 7.97 and 8.37 months, respectively. Low-KRAS tumors had a higher frequency of additional mutations in PIK3CA when compared with high-KRAS (6/10 versus 8/35). KRAS and NRAS mutations are usually present in the majority of neoplastic cells, whereas BRAF and PIK3CA mutations often affect a limited fraction of transformed cells. Resistance to cetuximab in low-KRAS patients might be driven by the complex mutational profile rather than KRAS mutation load.