Mimicry of Minute Pulmonary Meningothelial-like Nodules to Metastatic Deposits in a Patient with Infiltrating Lobular Carcinoma: A Case Report and Review of the Literature

Pathological diagnosis and immunohistochemical analysis of minute pulmonary meningothelial-like nodules: A case report

BACKGROUND

Minute Pulmonary Meningothelial-like Nodules (MPMNs) are rare benign pulmonary nodules, which are more common in elderly women and have a higher detection rate in lung tissues of patients with lung malignant diseases. Its origin is not yet clear. At present, there are few reports on the diagnostic methods such as imaging and pathological manifestations of MPMNs. This article reports a 70-year-old female patient with pulmonary adenocarcinoma combined with MPMNs and reviews of the relevant literature.

CASE SUMMARY

A 70-year-old women was admitted to our institution with feeling sour in her back and occasional cough for more than 2 mo. Computerized electronic scanning scan and 3D reconstruction images in our institution showed there were multiple ground-glass nodules in both of her two lungs. The biggest one was in the apicoposterior segment of left upper lobe, about 2.5 mm × 9 mm in size. We performed thoracoscopic resection of the left upper lung apicoposterior segment of the patient, and the final pathological report was minimally invasive adenocarcinoma. Re-examination of high resolution computed tomography 21 mo after surgery showed multiple ground-glass nodules in both lungs, and a new ground-glass nodule was found in the superior segment of the right lower lobe. We took pathological biopsy of the right upper lung and right lower lung nodules for the patient under thoracoscopy. The histomorphology of the right lower lobe nodule showed multiple lesions in the lung tissue, and the small foci in the alveolar septum were distributed in mild form of the aggregation of short spindle cells. The immunohistochemistry showed that the lesion was epithelial membrane antigen (EMA) (+), somatostatin receptor 2a (SSTR2a) (+), S-100 (-), chromogranin A (-), Syn (-), cytokeratin (-) and HMB-45 (-). The final diagnosis was minimally invasive adenocarcinoma, accompanied by MPMNs. We recommend that patients continue to receive treatment after surgery and to do regular follow-up observations.

CONCLUSION

The imaging manifestations of MPMNs are atypical, histomorphology and immunohistochemistry can assist in its diagnosis. This article reviews the relevant literature of MPMNs immunohistochemistry and shows that MPMNs are positive for EMA, SSTR2a, and progesterone receptor.

[Recent Advances and Controversies in Minute Pulmonary Meningothelial-like Nodules]

Minute pulmonary meningothelial-like nodules (MPMNs) are benign small lesions in the lungs, with similar pathological characteristics to the meningeal epithelium. MPMNs have similar imaging manifestations to malignant tumors, which can lead to misdiagnosis in clinical practice. There is no consensus on the pathogenesis of MPMNs, with some suggest that MPMNs derive from reactive proliferation, while others suggest that MPMNs share a common origin and molecular mechanism with meningiomas in the central nervous system. Understanding the characteristics of MPMNs and studying their pathogenesis will help improve the understanding and diagnosis of MPMNs. In this article, we reviewed the clinical, pathological, imaging characteristics, differential diagnosis and pathogenesis of MPMNs. We also analyze the existing research advances regarding the pathogenesis and propose prospects for further research.
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Diffuse Pulmonary Meningotheliomatosis: Clinic-Pathologic Entity or Indolent Metastasis from Meningioma (or Both)?

Pulmonary minute meningothelial-like nodules (MMNs) are common incidental findings in surgical specimens, consisting of tiny proliferation (usually no larger than 5-6 mm) of bland-looking meningothelial cells showing a perivenular and interstitial distribution, sharing morphologic, ultrastructural, and immunohistochemical profiles with meningiomas. The identification of multiple bilateral MMNs leading to an interstitial lung disease characterized by diffuse and micronodular/miliariform patterns radiologically allows the diagnosis of diffuse pulmonary meningotheliomatosis (DPM). Nevertheless, the lung is the most common site of metastatic primary intracranial meningioma, and differential diagnosis with DPM may be impossible without clinic-radiologic integration. Herein, we report four cases (three females; mean age, 57.5 years) fitting the criteria of DPM, all incidentally discovered and histologically evidenced on transbronchial biopsy (2) and surgical resection (2). All cases showed immunohistochemical expression of epithelial membrane antigen (EMA), progesterone receptor, and CD56. Notably, three of these patients had a proven or radiologically suspected intracranial meningioma; in two cases, it was discovered before, and in one case, after the diagnosis of DPM. An extensive literature review (44 patients with DPM) revealed similar cases with imaging studies excluding intracranial meningioma in only 9% (4 of 44 cases studied). The diagnosis of DPM requires close correlation with the clinic-radiologic data since a subset of cases coexist with or follow a previously diagnosed intracranial meningioma and, thus, may represent incidental and indolent metastatic deposits of meningioma.

Diffuse pulmonary meningotheliomatosis with pan-TRK expression by immunohistochemistry: a novel finding and potential pitfall

BACKGROUND

Pulmonary meningothelial-like nodules (PMNs) are benign proliferations of unclear clinical significance. They are mainly asymptomatic lesions that are usually discovered during the pathologic evaluation of resected pulmonary specimens or following post-mortem examination. Diffuse pulmonary meningotheliomatosis (DPM), which presents as bilateral multiple PMNs throughout the lungs, has been described less frequently. DPMs are benign lesions associated with both neoplastic and non-neoplastic pulmonary conditions.

CASE PRESENTATION

We report the case of a 59-year-old female patient who presented with a history of cough. Computerized tomography (CT) imaging revealed multiple subcentimeter bilateral pulmonary nodules. transbronchial biopsies were obtained which revealed foci of nodular interstitial proliferations composed of epithelioid to spindled cells in a vague whorled pattern. Immunohistochemical stains were diffusely positive for EMA and progesterone receptor. Furthermore, pan-TRK exhibited strong and diffuse membranous expression in the lesional cells. INSM1 was negative for expression. RNA-based next-generation sequencing for the detection of NTRK fusions was performed and was negative for gene rearrangements involving NTRK1, NTRK2, and NTRK3.

CONCLUSION

Here, we report a rare case of DPM and report pan-TRK expression in PMNs which has not been described. We provide a brief review of the literature and provide insight into the potential physiologic nature of PMNs. Lastly, we emphasize the recognition of pan-TRK immunoexpression in PMNs to avoid potential diagnostic errors.

Benign disease prone to be misdiagnosed as malignant pulmonary nodules: Minute meningothelioid nodules

Background

The lung is one of the most common target organs for malignant tumor metastasis. The existence of lung metastasis may have a decisive effect on the choice of treatment regimen. Minute pulmonary meningothelial‐like nodules (MPMNs) usually present as ground‐glass opacity or solid nodules, mimicking the imaging findings of malignant pulmonary nodules. This study summarizes the clinical, radiological, and pathological features of MPMNs to distinguish them from malignant pulmonary nodules.

Methods

The Guangdong Lung Cancer Institute Pathology Information System was searched using the key words “minute meningothelioid nodules” and “lung.” Patients who underwent pulmonary resection from 23 February 2009 to 31 May 2017 were included in the study. The 11th edition of Rosai and Ackerman's Surgical Pathology was used to confirm the diagnosis. The clinical, imaging, and pathological characteristics of MPMNs were recorded.

Results

Twelve patients had MPMNs. MPMNs were associated with cancerous or precancerous lesions (10/12), female gender (11/12), and non‐smokers (11/12). Four patients were misdiagnosed with malignant pulmonary nodules before surgery. Positron emission tomography‐computed tomography revealed an increased maximum standardized uptake value in one patient. Immunohistochemistry identified eight specimens positive for vimentin, EMA, and PR and negative for TTF‐1 and CK.

Conclusions

MPMNs tend to coexist with malignant tumors, mimicking the imaging findings of malignant pulmonary nodules, thus resulting in misdiagnosis. Dynamic monitoring or an invasive examination may help to distinguish MPMNs from malignant lesions.

Minute pulmonary meningothelial-like nodules simulating hematogenous lung metastasis: a case report

A 52-year-old man was referred to our clinic for an 11.3 mm nodule in the left lower lobe that was discovered on a chest computed tomography (CT) scan. Eleven small nodules were subsequently found in both lungs. Initially, we performed a transthoracic needle aspiration using CT scan guidance. The pathologic report showed a few clusters of atypical cells that were suspicious for malignancy. The positron emission tomography images revealed multiple lung nodules scattered throughout both lungs. The largest nodule (11.3 mm) in the left lower lobe did not have any discernible fludeoxyglucose uptake. For pathologic confirmation, we consulted a thoracic surgeon to perform the video-assisted thoracoscopic surgery. The final diagnosis was minute pulmonary meningothelial-like nodules (MPMNs). MPMNs are benign in nature, and only a few cases require treatment. However, when clinicians are suspicious of potential malignancy, a pathological correlation is essential, even if the final diagnosis is MPMNs.

Diffuse pulmonary meningotheliomatosis diagnosed by transbronchial lung biopsy

Minute pulmonary meningothelial-like nodules (MPMNs) are usually unique lesions in the lung parenchyma. Diffuse pulmonary meningotheliomatosis, which is presented as multiple MPMNs, has been less frequently described. MPMNs are mainly asymptomatic and are diagnosed after lung surgery or during autopsy. We report on a patient with multiple and bilateral pulmonary nodules, some of which were cavitated, diagnosed with diffuse pulmonary meningotheliomatosis by transbronchial lung biopsy. Diffuse pulmonary meningotheliomatosis should be included in the differential diagnosis of bilateral lung nodules.