Larsen, Brandon T.

We have identified 25 lesions involving alveolar lung parenchyma characterized by nodular proliferation of bland bilayered bronchiolar-type epithelium containing a continuous layer of basal cells. These lesions shared some histologic features with the recently described entity of ciliated muconodular papillary tumor (CMPT); however, the majority did not fit all diagnostic criteria in that they exhibited only focal or absent papillary architecture, and they had variable number of ciliated and mucinous cells, with some lesions entirely lacking 1 or both of these components. The morphologic and immunohistochemical features ranged from those resembling proximal bronchioles (proximal-type: moderate to abundant mucinous and ciliated cells; negative or weak TTF1 in luminal cells; n=8) to those resembling respiratory bronchioles (distal-type: scant or absent mucinous and ciliated cells; positive TTF1 in luminal cells; n=17). The hallmark of all lesions was a continuous layer of basal cells (p40 and CK5/6-positive). We provisionally designated these lesions as bronchiolar adenomas (BAs) and analyzed their clinicopathologic and molecular features. All BAs were discrete, sharply circumscribed lesions with a median size of 0.5 cm (range, 0.2 to 2.0 cm). Most lesions were either entirely flat (n=14) or contained focal papillary architecture (n=7); only 4 lesions, all proximal-type, were predominantly papillary, fitting the classic description of CMPT. Notably, of 9 lesions submitted for frozen section evaluation, 7 were diagnosed as adenocarcinoma. No postsurgical recurrences were observed for any lesions (median follow-up, 11 mo). Twenty-one BAs underwent next-generation sequencing and/or immunohistochemistry for BRAF V600E, revealing mutation profiles similar to those previously described for CMPTs, including BRAF V600E mutations (n=8, 38%), unusual EGFR exon 19 deletions (n=2, 10%), EGFR exon 20 insertions (n=2, 10%), KRAS mutations (n=5, 24%), and HRAS mutations (n=1, 5%). The mutation profiles were similar in proximal-type and distal-type lesions. In conclusion, we describe a family of putatively benign clonal proliferations with a spectrum of morphology recapitulating various levels of the bronchiolar tree, of which only a minor subset fits the classic description of CMPT. Comparable mutation profiles and partially overlapping morphologic features across the spectrum of these lesions support their nosological relationship. We propose designating this entire family of lesions as BAs, and that lesions currently designated CMPTs represent a subgroup of this family.

Mycobacterial spindle cell pseudotumor (MSP) is a rare benign spindle cell lesion containing acid-fact mycobacteria. These lesions are most commonly identified in the lymph nodes, skin, spleen, or bone marrow of immunocompromised patients and only rarely involve the lungs. We report 3 cases of pulmonary MSP, which include 2 patients who are known to be HIV-positive. The histopathological diagnosis of MSP in the lung lends itself to many challenges due to its rare incidence and its spindled tumor-like appearance. The differential diagnosis is broad and includes both benign and malignant entities. We highlight the importance of the clinical context in which these lesions typically present and the morphologic spectrum of features seen, and we offer a practical approach to the workup of pulmonary mycobacterial pseudotumor. Appropriate recognition of this entity should lead to an accurate diagnosis of a treatable benign condition despite the clinical presentation often favoring malignancy.

AbstractBackground and objectiveIdiopathic pulmonary fibrosis (IPF) is increasingly diagnosed by clinical and computed tomography (CT) criteria; however, surgical lung biopsy (SLB) may still be required in patients who lack definite CT features of usual interstitial pneumonia (UIP). We reviewed a cohort of elderly patients who underwent SLB, to evaluate the benefit of SLB in diagnosing idiopathic interstitial pneumonia (IIP).MethodsWe searched the pathology records of Mayo Clinic for ambulatory patients at least 75 years old, who underwent SLB between 2000 and 2012 for indeterminate IIP. Histologic slides were reviewed and clinical data were extracted from the record.ResultsA total of 55 patients (35 male) were enrolled. Median (interquartile range) age was 77 (76–80) years. Forced vital capacity was 70 (61–76)% and diffusing capacity of the lungs for carbon monoxide was 48 (42–54)% of predicted. In total, 37 (67%) patients had IPF, including 61% of those with HRCT findings inconsistent with UIP. Thirty‐day mortality was 10% and 90‐day mortality was 15%.ConclusionThe high mortality rate of SLB complicates the risk–benefit analysis in elderly patients with IIP. The expected value of the SLB is probably highest when the HRCT features are inconsistent with UIP, due to the frequent (39%) retrieval of patterns other than UIP.

Osteosarcoma (OS) is a malignant bone tumor which is found primarily in adolescents, with the distal femur as the most common location. OS with a jaw primary is present in only about 10% of cases and the risk of recurrence is considered to be decreased in the jaw versus other primary locations. We present a unique case of a patient with localized OS of the jaw with an isolated recurrence in her bone marrow almost 5 years after completion of initial treatment.

Context.— Idiopathic pulmonary fibrosis (IPF) is a distinctive clinicopathologic entity and the most common form of progressive diffuse lung scarring in older adults. Idiopathic pulmonary fibrosis manifests histopathologically as the usual interstitial pneumonia pattern. The usual interstitial pneumonia pattern is distinguished by geographically and temporally heterogeneous fibrosis that is peripherally accentuated, often with honeycombing and traction bronchiectasis. Idiopathic pulmonary fibrosis is not the only disease that leads to end-stage lung fibrosis, however, and several other entities may also cause advanced fibrosis. Surgical lung biopsies often present a diagnostic dilemma when they show clear evidence of advanced fibrosis, but the clinical, imaging, and/or histopathologic subcharacteristics suggest something other than IPF. Objective.— To address this dilemma, we review several other fibrotic lung diseases, including connective tissue disease–associated interstitial lung disease, chronic hypersensitivity pneumonitis, advanced pulmonary Langerhans cell histiocytosis, end-stage pulmonary sarcoidosis, Erdheim-Chester disease, Hermansky-Pudlak syndrome, and others, detailing their clinical, radiologic, and histopathologic attributes and emphasizing similarities to and differences from IPF. Data Sources.— Data sources comprised published peer-reviewed literature and personal experience of the authors. Conclusions.— Often, clues in the lung biopsy may offer the first suggestion of a fibrotic lung disease other than IPF, and accurate classification is important for prognosis, treatment, and the development of future therapies.

Background Idiopathic dilated cardiomyopathy ( DCM ) is typically diagnosed in adulthood, yet familial cases exhibit variable age‐dependent penetrance and a subset of patients develop sporadic DCM in childhood. We sought to discover the molecular basis of sporadic DCM in an 11‐year‐old female with severe heart failure necessitating cardiac transplantation. Methods and Results Parental echocardiograms excluded asymptomatic DCM . Whole exome sequencing was performed on the family trio and filtered for rare, deleterious, recessive, and de novo variants. Of the 8 candidate genes identified, only 2 had a role in cardiac physiology. A de novo missense mutation in TNNT 2 was identified, previously reported and functionally validated in familial DCM with markedly variable penetrance. Additionally, recessive compound heterozygous truncating mutations were identified in XIRP 2 , a member of the ancient Xin gene family, which governs intercalated disc ( ICD ) maturation. Histomorphological analysis of explanted heart tissue revealed misregistration, mislocalization, and shortening of ICD s, findings similar to Xirp2 −/− mice. Conclusions The synergistic effects of TNNT 2 and XIRP 2 mutations, resulting in perturbed sarcomeric force generation and transmission, respectively, would account for an early‐onset heart failure phenotype. Whereas the importance of Xin proteins in cardiac development has been well established in animal models, this study implicates XIRP 2 as a novel modifier gene in the pathogenesis of DCM .

Aims Prognostication and treatment selection for cardiac amyloidosis requires accurate amyloid typing. The aim of this study was to investigate the utility of histomorphology for predicting type. Methods and results Autopsy cases with cardiac amyloidosis (1998–2010) were typed by the use of mass spectrometry‐based proteomics. Deposition patterns were correlated with amyloid type. Among 108 decedents (mean age 75 years; 69% men), 107 had a single type, including transthyretin (ATTR) (60 cases), amyloid light chain (AL) (32 λ; 12 κ), amyloid A (AA) (two), and apolipoprotein AIV (AApoAIV) (one). Interstitial deposition was more extensive in AL amyloidosis cases than in ATTR cases [odds ratio (OR) 6.8, P = 0.0004]. Histomorphological patterns of interstitial deposition were mixed in 61% of AL amyloidosis cases and in 61% of ATTR cases, but diffuse pericellular deposits favoured AL amyloidosis (OR 10.7, P = 0.0001), nodular deposits favoured ATTR (OR 3.1, P = 0.0229), and discrete pericellular deposits tended to partially favour ATTR (OR 1.7, P = 0.1970). Arterial and venous deposits each favoured AL amyloidosis (OR ranging from 9.3 to 192.0, P‐value ranging from 0.0022 to <0.0001), and were severe in AL amyloidosis. Endocardial deposits favoured AL amyloidosis (OR 46.3, P < 0.0001) and were also more severe in AL amyloidosis. Conclusions The extent and distribution of cardiac amyloidosis strongly correlate with amyloid type, suggesting fundamental differences in the pathobiology of deposition. The tendency for mixed patterns to occur limits the practicality and accuracy of using histopathology for amyloid typing.

Intravesical instillation of Bacillus Calmette-Guérin (BCG) is a mainstay of adjunctive therapy for superficial bladder cancer. Disseminated BCG infection (“BCG-osis”) after this therapy is rare and potentially life-threatening; only isolated case reports detail the histopathologic findings thereof, few of which had a diagnosis confirmed by molecular testing. We report 3 additional cases of BCG-osis complicating BCG therapy, all confirmed by cultures and molecular assays, including the first cases of wedge biopsy-confirmed BCG pneumonia and BCG olecranon bursitis. When suggested by a relevant clinical history, recognition of randomly distributed granulomas in any organ should prompt consideration of BCG-osis and liberal performance of AFB stains, aided by targeted molecular assays. Physicians should maintain a high index of suspicion when miliary infiltrates arise after intravesical BCG instillation, and close multidisciplinary communication is essential. Pathologist awareness of this rare cause of granulomatous inflammation aids recognition of BCG-osis and facilitates prompt initiation of antimycobacterial therapy.

Bronchial atresia is a rare pulmonary developmental anomaly characterized by the presence of a focal obliteration of a segmental or lobar bronchial lumen. The lung distal to the atretic bronchus is typically emphysematous along with the presence of mucus filled ectatic bronchi (mucoceles). BA is usually asymptomatic but pulmonary infections can rarely develop in the emphysematous lung distal to the atretic bronchus. We present a unique case of chronic pulmonary aspergillosis (CPA) in a patient with BA with no evidence of immune dysfunction. The patient was treated initially with voriconazole and subsequently underwent surgical excision of the involved area. On follow-up, she has done extremely well with no evidence for recurrence. In summary, we describe the first case of chronic pulmonary aspergillosis in an immunocompetent patient with bronchial atresia.