Malignant mesothelioma is a rare malignancy of serosal-lined tissues. It has been recognized since the last century that the majority of pleural mesotheliomas are caused by exposures to asbestos, a fibrous silicate mineral that was used extensively in the construction trades for its insulating properties. A previously unrecognized source of asbestos exposure is cosmetic talc that has been widely used for personal hygiene and other purposes by adults and children. Since 2014, more than 200 cases of mesothelioma have been reported in individuals, whose only known source of asbestos exposure was cosmetic talc. In this chapter the association of talc with malignant mesothelioma will be reviewed.

Nuclear protein in testis (NUT) carcinoma, an aggressive tumour driven by NUTM1 rearrangements, often involves the lung/mediastinum and shows squamous differentiation. We encountered an index patient with a thoracic NUT carcinoma diagnosed by molecular testing, showing extensive pleural involvement and diffuse thyroid transcription factor‐1 (TTF‐1) expression, initially suggestive of lung adenocarcinoma with pseudomesotheliomatous growth. We thus gathered an institutional series of thoracic NUT carcinomas to examine their pathological spectrum.

BACKGROUND:Asbestos is the primary known cause of malignant mesothelioma. Some cosmetic talc products have been shown to contain asbestos. Recently, repeated exposures to cosmetic talc have been implicated as a cause of mesothelioma. METHODS:Seventy-five individuals (64 females; 11 males) with malignant mesothelioma, whose only known exposure to asbestos was repeated exposures to cosmetic talcum powders, were reviewed in medical-legal consultation. Out of the 75 cases, 11 were examined for asbestiform fibers. RESULTS:All subjects had pathologically confirmed malignant mesothelioma. The mean age at diagnosis was 61 ± 17 years. The mean latency from exposure to diagnosis was 50 ± 13 years. The mean exposure duration was 33 ± 16 years. Four mesotheliomas (5%) occurred in individuals working as barbers/cosmetologists, or in a family member who swept the barber shop. Twelve (16%) occurred in individuals less than 45 years old (10 females; 2 males). Forty-eight mesotheliomas were pleural (40 females; 8 males), 23 were peritoneal (21 females; 2 males). Two presented with concomitant pleural and peritoneal disease. There was one pericardial, and one testicular mesothelioma. The majority (51) were of the epithelioid histological subtype, followed by 13 biphasic, 8 sarcomatoid, 2 lymphohistiocytoid, and 1 poorly differentiated. Of the 11 individuals whose nontumorous tissues were analyzed for the presence of asbestiform fibers, all showed the presence of anthophyllite and/or tremolite asbestos. CONCLUSIONS:Mesotheliomas can develop following exposures to cosmetic talcum powders. These appear to be attributable to the presence of anthophyllite and tremolite contaminants in cosmetic talcum powder.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive form of interstitial lung disease (ILD). High-resolution CT (HRCT) is currently used to identify macroscopic IPF features. However, for 50% of patients, ultimate diagnosis relies on microscopic features from invasive, high-risk surgical biopsies (SLBX). We conducted a pilot study to assess endobronchial OCT (EB-OCT) for in vivo diagnosis of IPF, enrolling ILD patients with nondiagnostic HRCT undergoing SLBX. EB-OCT visualized salient IPF features, including microscopic features not visible on HRCT, and accurately diagnosed IPF and non-IPF ILD as compared with SLBX. EB-OCT has the potential for in vivo microscopic diagnosis of IPF.

Malignant mesothelioma is a rare and aggressive cancer most typically associated with prior asbestos exposure. The nature of the relationship between asbestos exposure and hereditary familial syndromes predisposing to malignancy has not been determined. We report two Lynch syndrome patients with paraoccupational asbestos exposure who developed diffuse malignant mesothelioma of the pleura or peritoneum. Interestingly, one showed a separate focus of pleural well-differentiated papillary mesothelioma. It is likely that Lynch syndrome patients are at increased risk for the development of mesothelioma in the setting of exposure to asbestos, even at what is generally considered to be low levels. In the presence of a documented history of low-level asbestos exposure, patients with genetic predisposition disorders (including Lynch syndrome) should be considered to have an independent risk factor modifying the effects of asbestos exposure.

Calcifying fibrous pseudotumor (CFP) is a rare, benign soft tissue tumor that may uncommonly arise in the pleura. These tumors can show multifocal dissemination across the pleural surface, but the mechanism underlying this dissemination is unclear. Review of previously reported cases of pleural CFP demonstrates a strong predilection for basal and diaphragmatic pleural surfaces, and a significantly higher rate of multifocality compared with other locations. We present a 59-year-old male with multiple CFP of the pleura. Reactive-appearing adhesions spanning the pleural surfaces were present, and by electron microscopy, were involved by tumor. We suggest this is the likely mode of dissemination across the pleural surfaces.

Improved tools have led to a burgeoning understanding of lung regeneration in mice, but it is not yet known how these insights may be relevant to acute lung injury in humans. We report in detail two cases of fulminant idiopathic acute lung injury requiring extracorporeal membrane oxygenation in previously healthy young adults with acute respiratory distress syndrome, one of whom required lung transplantation. Biopsy specimens showed diffuse alveolar injury with a striking paucity of alveolar epithelial regeneration, rare hyaline membranes, and diffuse contiguous airspace lining by macrophages. This novel constellation was termed diffuse alveolar injury with delayed epithelization. In addition, mirroring data from murine models of lung injury/regeneration, peribronchiolar basaloid pods (previously described as squamous metaplasia) and ciliated bronchiolarization were identified in these patients and in 39% of 57 historical cases with diffuse alveolar damage. These findings demonstrate a common and clinically relevant human disease correlate for murine models of severe acute lung injury. Evidence suggests that peribronchiolar basaloid pods and bronchiolarization are related spatially and temporally and likely represent overlapping sequential stages of the response to severe distal airway injury.

Idiopathic pulmonary fibrosis (IPF) requires diagnostic certainty to stratify prognosis and therapeutic decision-making. HRCT lacks microscopic resolution, which precludes definitive diagnosis in a large fraction of cases. Histologic diagnosis requires invasive surgical biopsy, which has risks of morbidity and mortality. There is a clear need for a low-risk method to microscopically diagnose IPF. Optical coherence tomography (OCT) is an imaging modality that is compatible with bronchoscopy, can access the peripheral lung, and rapidly assess large tissue volumes with microscopic resolution (<10μm) well beyond HRCT capabilities. We aim to determine whether endobronchial OCT can detect microscopic features of interstitial lung disease (ILD), and distinguish IPF from non-IPF ILD. We conducted in vivo endobronchial OCT in ILD patients (n=15) undergoing diagnostic biopsy. OCT and biopsy interpretations were performed independently, and compared. OCT imaging totaled <10 minutes, and microscopically assessed more sites and lung volume than corresponding biopsies. Endobronchial OCT was able to identify IPF and non-IPF ILD in patients with non-diagnostic HRCT. OCT visualized salient diagnostic features, including microscopic honeycombing in IPF not seen on HRCT and traction bronchiectasis in non-IPF ILD that caused diagnostic confusion on HRCT. OCT has significant potential to serve as a low-risk microscopic complement to HRCT for diagnosis of IPF.

Perivascular epithelioid cell tumor (PEComa), mesenchymal tumors morphologically characterized by epithelioid cells, coexpress melanocytic and muscle markers. Herein, we describe a heretofore-undescribed tuberous sclerosis complex (TSC)-related neoplasm, morphologically resembling a soft tissue fibroma-like lesion, but showing an immunophenotype resembling PEComa. We identified 3 soft tissue fibroma-like lesions in individuals with TSC. We also evaluated 6 TSC-related periungual fibroma as well as a range of non-TSC fibroma-like lesions (n=19). Immunohistochemistry for HMB-45, desmin, smooth muscle actin, TFE3, and S100 was performed on the TSC-related fibromas. Periungual fibromas and non-TSC fibroma-like lesions were also stained for HMB-45. All 3 TSC patients were female, ranging in age from 4 to 51 years (mean, 26.7y). Two tumors were located in extremities and 1 on the chest wall. The tumors showed elongated to stellate spindle-shape cells, prominent collagenous background, and lacked mitotic activity and cytologic atypia. Immunohistochemically, all 3 tumors were positive for HMB-45; smooth muscle actin or desmin was positive in both tumors tested. TFE3 was negative. All patients were alive with no evidence of disease with median follow-up of 55 months (range, 6 to 131mo). Non-TSC fibroma-like lesions and oral and periungual fibromas were negative for HMB-45. Fibroma-like PEComa, a newly recognized soft tissue tumor with a strong association with TSC, mimics soft tissue fibroma but shows reactivity with melanocytic markers.

The structure of the lung determines its function. The various compartments of the lung are specially adapted to serve the activities of the lung. Pulmonary pathology is defined by the changes that occur in the underlying anatomy of the lung.

Lung allograft transplantation remains the only potential curative treatment for a number of life-threatening diseases. However, lung transplantation is an arduous approach due to the propensity of the immune system to reject allografts.

BackgroundCigarette smoke and asbestos are recognized causes of lung carcinoma and together promote carcinogenesis. Adenocarcinoma is currently the most common cause of lung cancer in the USA and it has been linked to both smoking and asbestos exposure. Mutations in the epidermal growth factor gene receptor (EGFR) occur predominantly in non‐smokers with adenocarcinoma.Methods Mutations in the EGFR gene were investigated using next‐generation sequencing.ResultsWe report the presence of EGFR exon point mutations in the pulmonary adenocarcinomas of three never‐smokers occupationally exposed to asbestos.ConclusionThe role of asbestos as a possible cause of EGFR mutagenesis requires further investigation. Am. J. Ind. Med. 60:306–309, 2017. © 2017 Wiley Periodicals, Inc.

The reaction patterns of each of the compartments of the lung are largely stereotypic. To assess pulmonary pathology, one should become conversant with the temporal sequences of pulmonary inflammation.