Solitary Endobronchial Plasmacytoma: A Rare and Easily Misdiagnosed Entity

Pooja Phalak¹, Shailee Mehta², Sanjiban Patra², Priti Trivedi³, Prerna Walia¹

1. DM Resident, Dept. of OncoPathology, The Gujarat Cancer and research Institute, Ahmedabad.

2. Assistant Professor, Dept. of OncoPathology, The Gujarat Cancer and research Institute, Ahmedabad. 

3. Professor and Head, Dept. of OncoPathology, The Gujarat Cancer and research Institute, Ahmedabad.

*Correspondence to: Dr. Priti Trivedi. Professor and Head, Department of OncoPathology, , Gujarat Cancer and research institute, New civil hospital campus, Ahmedabad-380016.

Copyright

© 2023 Dr. Priti Trivedi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 08 June 2023

Published: 01 July 2023

Abstract

Solitary endobronchial plasmacytoma is a rare type of extramedullary plasmacytoma. It can be misdiagnosed as other tumour like neuroendocrine tumour in view of its plasmacytoid and near uniform cytological features. Here, we report a case of a 51year old gentleman who presented with chest pain and dyspnoea. On radiology, an endobronchial mass was detected and biopsy was performed for tissue diagnosis which was inconclusive. Surgical resection was planned along with frozen section. Frozen section was reported as neuroendocrine tumour.  But in paraffin section with the help of immunohistochemistry the final diagnosis was rendered as plasma cell neoplasm with extensive amyloid material and involvement of a single hilar lymph node. The workup for multiple myeloma was negative.

Keyword: Extramedullary plasmacytoma, Amyloid, Solitary endobronchial plasmacytoma.

Introduction

Extramedullary plasmacytoma (EMP) is a rare type of plasma cell neoplasm without bone marrow involvement or other systemic features of multiple myeloma, comprising of 3-5% of all plasma cell neoplasms, affecting the head and neck including upper aerodigestive tract in 80% of cases. [1,2] Primary endobronchial presentation is very rare.

Case Presentation

A 51year old gentleman with smoking habit, presented with complaints of chest pain, cough and dyspnea at our hospital. Physical examination was normal. A routine laboratory workup and ECG were within normal limits. Chest Xray revealed blunting of left CP angle with homogenous opacity in left middle and lower zone and obliteration of left dome of diaphragm; possibility of left mild pleural effusion appears likely.

A computed tomography (CT) scan of thorax, abdomen and pelvis showed 32 x 28 x 45mm lesion involving mediobasal segment of left lower lobe of lung, which is encasing the bronchus with intrabronchial growth. There were subcentrimetric nodes in preparatracheal, precarinal and subcarinal region. Rest of the CT scan was unremarkable. (Figure A) Bronchoscopy showed polypoidal intrabronchial lesion at left main bronchus with luminal narrowing. Bronchoscopy guided biopsy and fine needle aspiration cytology was performed and reported as non-representative material showing chronic inflammation and haemorrhage. Brochioloalveolar lavage was reported as negative for malignant cells. Subsequent CT guided biopsy was performed and it also showed fibrocollagenous tissue with admixed chronic inflammatory cells. Hence, patient was planned for surgical resection along with diagnostic frozen section. Frozen section showed monomorphic tumour cells arranged in nests and sheets separated by eosinophilic material. Tumor cells showed eccentric nucleus with eosinophilic cytoplasm. It was reported as neuroendocrine tumour on frozen section. (Figure B) Left lower lobectomy and lymphnode dissection (AP window, subcarinal and hilar) was performed. On gross examination, it was a unifocal well circumscribed polypoidal mass arising from left main bronchus measuring 55 x 35 x 30 mm in size which was grey white to brown in appearance on cut surface (Figure C). The lesion was 0.5cm away from pleural surface. Bronchial cut margin was 1cm away and vascular cut margin was 1.2cm away from lesion. Superior and inferior lung parenchymal resection margins were 2cm and 4cm away from lesion. Rest of the lung parenchyma was unremarkable. Three hilar lymphnodes were identified from the resection specimen with largest lymphnode measuring 0.8cm. One hilar, two subcarinal and two AP window lymphnodes were identified from separately sent containers, size of largest lymphnode was 1.4cm. On microscopy, the tumour showed diffuse sheets of plasmacytoid cells with intervening eosinophilic homogenous material. These tumour cells were arranged without any insular / trabecular pattern. Tumour cells showed eccentric nuclei, cartwheel like chromatin and amphophilic cytoplasm. At places, these cells were also showing bi and multinucleation. There was no evidence of necrosis or mitoses. (Figure D, E) On the basis of these findings, differential diagnosis considered were neuroendocrine tumour and plasma cell neoplasm. Immunohistochemistry was done. Tumour cells were immunoreactive for EMA, CD38, CD138 and immunonegative for synaptophysin, chromogranin, AE1, LCA, CD20 and CD3. Tumour cells were positive for lambda chain and negative for kappa chain. (Figure F,G, H, I)  Congo red stain was performed for confirmation of amyloid material and it showed apple green birefringence on polarised microscopy.

(Figure J) So the final diagnosis was solitary plasmacytoma with amyloid material. One hilar lymphnode out of total eight submitted lymphnodes was involved by plasmacytoma. Further myeloma workup was advised. Serum light chain assay and kappa: lambda ratio were within normal limits. Serum protein electrophoresis revealed normal pattern with all major fractions within normal limit and absence of monoclonal band. So, the final diagnosis of solitary endobronchial plasmacytoma was considered. The patient had an uneventful postoperative recovery. On follow up, at three months interval, the patient was doing well without any further complaints.

Discussion

Extramedullary plasmacytoma is a rare type of plasma cell neoplasm and has two major subtypes, primary and secondary, defined by without and with marrow involvement by plasma cells, respectively. [3] Pulmonary involvement is itself rare and usually confined to the lung parenchyma[4], whereas solitary endobronchial presentation is extremely rare with only a few reported cases so far.[5-9]

A systematic case review of endobronchial plasmacytoma revealed that this tumour has an elderly male predilection with wide age range 17-86 years. Common presenting complaints were cough and dyspnea. In majority of cases, the tumour was predominantly involving right and left main bronchus. Most cases were diagnosed by bronchoscopy. Treatment options were either surgery (resection or endoscopic removal) or radiation or combined surgery and radiation.

On the basis of histomorphology, differential diagnosis considered were neuroendocrine tumour, lymphoma, plasma cell neoplasm and rarely poorly differentiated carcinoma. Neuroendocrine tumour is positive for synaptophysin and chromogranin. Lymphoma cells are positive for LCA and poorly differentiated carcinoma is positive for CK. However, in our case all the above markers were negative. A hilar lymphnode was also showing involvement by plasmacytoma, similar to the case reported by Wei et al [13] and Pierd et al [14].

As per review of literature, 22% cases of extramedullary plasmacytoma had recurred and 16% were progressed to multiple myeloma, but there have been no case reports of primary endobronchial plasmacytoma progressed to multiple myeloma [3]. There is one case report of secondary endobronchial plasmacytoma in patient with a history of multiple myeloma [16]. However, because of high prevalence of recurrence and progression of extramedullary plasmacytoma, patients should be carefully monitored.

Our case indicates that primary endobronchial plasmacytoma, a rare presentation of extramedullary plasmacytoma, should be considered in the differential diagnosis of an endobronchial mass. Radiological studies and optimal histopathological evaluation will confirm the diagnosis. Treatment strategy will depend on the patient’s condition and the extent of the disease. Although there have been no reports of primary endobronchial plasmacytoma progressing to multiple myeloma, patients should be carefully monitored, given the possible progression of extramedullary plasmacytoma.

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