Clinical and cytopathologic characteristics of lymphoid neoplasms involved with serous effusions: a single center experience

Background: Lymphoid neoplasms in serous effusions (SEs) were uncommon. Currently, most reports of lymphoid neoplasms in SEs were from Western countries, but few reports were from China, and the details were still unclear. Methods: Between January 2004 and December 2019, lymphoid neoplasms diagnosed by cytological methods from specimens of pleural effusions (PEs), ascites, and pericardial effusions in our hospital were reviewed. Results: 59 patients of lymphoid neoplasms were diagnosed by SEs, the top three causes were diffuse large B-cell lymphoma (DLBCL) (n=21, 35.6%), myeloma (n=13, 22.0%), and T-lymphoblastic lymphoma (n=5, 8.5%). In PEs involved with DLBCL, the cytomorphology of DLBCL cells was variable, most PEs were present during tumor course (92.9%), bilateral PEs were the predominance (57.2%), and the median survival time was only 1.23 months after effusion. In PEs involved with myeloma, nearly all cases had a high ratio of immature to mature plasma cells (>1.0), IgA (36.4%) and light chain λ (36.4%) were the most frequently found. Bilateral PEs were easily found (90.9%), and the median survival time was only 1.4 months after effusion. Solitary plasmacytomas with myeloma infiltration in PEs seemed to have a better prognosis than that of plasma cell myeloma. Conclusion: Some differences are found between our patients and those from Western countries, and more studies involving different ethnic populations could help to elucidate the features of lymphoid neoplasms in SEs.


Introduction
Cytologic analysis of pleural effusion (PE), ascites, or pericardial effusion was often the first-line diagnostic test performed after an effusion was detected [1][2][3]. It was simple, safe, fast and cost effective. It reduced all of the possible consequences and 3 complications of a more aggressive biopsy procedure [3,4]. However, lymphoid neoplasms in serous effusions (SEs) were uncommon, and the diagnosis of lymphoid neoplasms in SEs was still challenging.
Cytopathologic diagnoses could determine whether or not neoplastic cells were present in SEs [2][3][4][5][6], but sometimes it was difficult to determine by cytomorphology alone. For example, indolent lymphoma often mimics a reactive lymphocytosis consisting predominantly of small cells, and plasma cells may present cytomorphologic features nearly identical to mesothelial cells in some effusions. Then a combination of clinical features, morphology, and immunophenotype or other ancillary techniques aided the correct diagnosis of lymphoid neoplasms in SEs [3][4][5].
Currently, most reports of lymphoid neoplasms in SEs were from Western countries [4][5][6][7][8][9], but few reports were from China, and the details were still unclear. Racial differences in some hematological malignancies had been reported before [10,11], so it was necessary to reveal the clinical and cytologic features of lymphoid neoplasms in SEs from China. In this study, we reviewed the lymphoid neoplasms diagnosed by SEs from our hospital, with a period of sixteen years.

Study Cases
Between January 2004 and December 2019, lymphoid neoplasms diagnosed by cytological methods from specimens of PEs, ascites, and pericardial effusions in our hospital were reviewed. The presence of lymphoid neoplasms cells in effusions was determined by cytology supplemented by immunocytochemistry (ICC), cell blocks with special studies, flow cytometry (FCM), polymerase chain reaction for clonality, and/ or conventional cytogenetics.

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Wright-Giemsa staining and Papanicolaou staining [3,4] were performed on alcohol-fixed smears and/ or liquid-based preparation slides. DiffQuik® staining [12] was performed on air-dry slides for some cases. Haematoxylin-eosin staining was performed on cell block sections. The smears, SurePath® liquid-based preparation slides and cell block sections were reviewed by two experienced pathologists. Data were collected on patients and clinical characteristics as well as results from one or multiple ancillary tests. This investigation was conducted after approval by the institutional review board of the second affiliated hospital, school of medicine, Zhejiang university.
All the diagnoses were in accordance with the criteria of world health organisation classification of tumours of haematopoietic and lymphoid Tissue (2017) [13,14]. For patients who had a previous history of lymphoid neoplasms, the results helped to confirm recurrence or transformation to an aggressive subtype. Cases of primary effusion lymphomas, or cases diagnosed by cytomorphology without support of other ancillary test findings had been excluded in advance.

Polymerase Chain Reaction Assays
To detect monoclonal gene rearrangements in immunoglobulin (Ig)H and Igκ, DNA was extracted from samples, and PCR amplification was performed using the BIOMED-2 primers as previously reported [17,18]. Appropriate positive, negative, and internal control samples were run with each specimen.

Fluorescence In Situ Hybridization Assays (FISH)
FISH was performed on the cell block or tissue sections as previously reported [19].

Characteristics of DLBCL in PEs
In our series, DLBCL was the most frequently found (n = 21, 35.6%). As most of the cases were from PEs, so we next focused on the characteristics of DLBCL in PEs (n = 14). It showed that 9 of 14 (64.3%) patients had a high percentage of immature lymphocytes (>50%) in PEs, and papillary projection of nuclei (13/14, 92.9%), cytoplasmic or nuclear vacuoles (10/14, 71.4%) were frequently found ( Figure 2, Table 1).
By Kaplan-Meier analysis, it showed that the survival time after effusion in PEs positive group was significantly shorter than that in PEs negative group (median, 1.23 vs 14.43 months, P = 0.000) (Figure 4).

Characteristics of myeloma in PEs
Myeloma was the second cause (n = 13, 29.3%) of SEs in our series. As most of myeloma were found in PEs (n = 11), so we also studied the features of myeloma in PEs. It showed that 6 of 11 (54.5%) patients had a high percentage of plasma cells (>50%) in PEs, but papillary projection of nuclei, cytoplasmic or nuclear vacuoles were hardly found ( Figure 3, Table 3).  (Figure 4).

Discussion
SEs occur in a number of malignancies, but lymphoid neoplasms in effusions are still uncommon. Recently, the data of lymphoid neoplasms in effusions are lacking from many parts of the world. It has been reported mostly as single case description or in reviews of multiple case reports from different institutions [20][21][22][23][24]. To the best of our knowledge, this study is the largest series of lymphoid neoplasms in effusions reported from China.
In our series, B-cell neoplasms in effusions are more frequently found than T-cell or NKcell neoplasms, which is contrast to some reports from Western countries [1,22,23]. The top three lymphoid neoplasms are DLBCL, myeloma, and T-LBL in order. DLBCL is the most frequently found not only in PEs, but also in ascites and pericardial effusions. Our hospital is not a specialized hospital but one famous general hospital in the east of China, so the specimens are unbiased. Nearly two-thirds of our patients with lymphoid neoplasms are diagnosed by PEs, therefore we pay more attention to the features of DLBCL and myeloma in PEs.
The cytomorphology of DLBCL cells in PEs is variable. Papillary projection of nuclei, cytoplasmic or nuclear vacuoles, mitoses and apoptosis are present in more than twothirds of our patients, but these features can also be easily seen in other lymphomas, such as Burkitt lymphoma, MALT lymphoma [25]. Some DLBCL cells also present cytomorphologic features similar to undifferentiated carcinoma or sarcoma, the distinction 9 is that most DLBCL cells distributed separately or scatteredly, rather than nest-like distribution as carcinoma or sarcoma. No unique morphologic feature of DLBCL cells in PEs is found in our series, and the correct diagnoses require the combination of cytomorphologic and other ancillary test findings.
In our series, IPI scores ≥3 and stage ≥3 are present nearly in all DLBCL patients involved with PEs, and bilateral PEs are found in more than half of the patients, which indicate the seriousness of this disease. Contrast to some other reports [4,26], 92.9% cases with effusions are present during tumor course in our study. BM involvement of DLBCL cells are usually more frequently found than PEs [25], but in our DLBCL patients with lymphoma cells in PEs, less than one-thirds of patients are found with BM involvement. The reason is unclear, maybe DLBCL in our patients invade the thoracic cavity more easily. Consistent with Chen et al [26], the prognosis of our patients with DLBCL in PEs is very poor, with the median survival time of 1.23 months after effusion. RCHOP-like treatment seems to have no significant improvement of survival.
PEs due to plasma cells infiltration are rare, with approximately 80 cases reported worldwide [8,27,28]. It may result from extension of adjacent subcutaneous, skeletal, or parenchymal plasmocytomas into the pleural space [8,13]. The cytomorphology of malignant plasma cells includes nuclear polymorphism, prominent nucleoli or asynchronous maturation of the nucleus in relation to the cytoplasm, mitoses and apoptosis, but papillary projection of nuclei, cytoplasmic or nuclear vacuoles are hardly found in our study. In addition to the help of other ancillary findings, the high ratio of immature to mature plasma cells (>1.0) are very helpful in differentiating reactive from malignant plasma cells infiltrates.
Our study shows that paraprotein type of IgA (36.4%) and light chain λ (36.4%) are the most frequently found, in contrast to the IgG predominance reported elsewhere [8,21,28].
The median percentage of plasma cells in bone marrow is significantly higher in PEs positive group than that in PEs negative group (76.5% vs 32.0%). It has been reported that left-sided PEs caused by myeloma are mostly seen in Western countries [29,30], but bilateral PEs (90.9%) are more easily found in our study. The prognosis of our patients with myeloma in PEs is very poor, the median survival time is only 1.4 months after effusion.
Interestingly, there is an unusual case in our series. A 69 years-old female patient with a right-sided pleural mass is diagnosed as solitary plasmacytomas with involvement of PEs, no monoclonal immunoglobulin or skeletal lesions was found. She received five courses of local chemotherapy with melphalan and prednisone by intrapleural injection, followed by two course of cisplatin and dexamethasone. Now the patient is still alive, with a survival time more than six years. It seems that solitary plasmacytomas with myeloma infiltration in PEs has a better prognosis than that of plasma cell myeloma. Due to the rarity of solitary plasmacytomas involved with PEs, it should be confirmed with more cases.
In conclusion, we reveal the prevalence of lymphoid neoplasms in SEs from China, and show the clinical and cytologic characteristics of DLBCL or myeloma involved with PEs. Some differences do exist between our patients and those from Western countries, and more studies from different ethnic populations should help to elucidate the features of lymphoid neoplasms in SEs.

Ethics approval and consent to participate
Our study was approved by the ethics committees of the second affiliated hospital, school of medicine, zhejiang university, according to the guidelines of the Declaration of Helsinki.
Additional patient consent for this retrospective study was not required.

Availability of data and materials
All data generated or analyzed during this study are included in this published article

Competing interests
The authors declare that they have no competing interests

Funding
This work was supported by national natural science foundation of China (No. 81400107).