Lesions described as nodular mesothelial hyperplasia are primarily composed of histiocytes

Cytomorphology of nodular histiocytic/mesothelial hyperplasia

Nodular histiocytic/mesothelial hyperplasia (NHMH) is a pathologic entity that has not been well characterized in the cytopathology literature. This is unfortunate because if unrecognized, NHMH may be misdiagnosed when encountered in cytology specimens. The aim of this communication is to accordingly alert cytologists about NHMH by means of an illustrative case report.

Intratubal Pseudopapillary Histiocytic Hyperplasia: A New Histologic Variant in the Spectrum of Histiocytic Lesions Involving the Fallopian Tube

Although histiocytic lesions of the fallopian tube are relatively rare compared to their epithelial counterparts, there exists a spectrum of histiocytic lesions involving the fallopian tube that are described under different terminologies dependent on the involved compartment of the fallopian tube. A common histologic denominator of all the hitherto reported tubal histiocytic lesions is the presence of sheets and clusters of histiocytes without any supportive connective tissue. The current study describes three cases of a heretofore-undescribed papillary histiocytic lesion in the lumen of the fallopian tube. All 3 lesions were characterized by avascular, hyaline collagenous papillary cores surrounded by a monotonous population of epithelioid cells, morphologically resembling mesothelial cell hyperplasia, but displaying a histiocytic immunophenotype with diffuse immunopositivity for CD68. Since the papillary cores did not harbor any vasculature, the term intratubal pseudopapillary histiocytic hyperplasia was proposed for this histiocytic proliferation which expands the spectrum of histiocytic lesions of the fallopian tube. Although probably of no clinical significance, practicing pathologists should be aware of this peculiar histiocytic lesion of the fallopian tube to avoid misdiagnosis and unnecessary immunohistochemical testing.

Signet ring cell mesothelioma; A diagnostic challenge

Signet ring cell mesothelioma is a rare variant of epithelioid mesothelioma with limited cases published. It has a male predilection and most commonly occurs on pleura; it can also arise in the peritoneal cavity. The signet ring cell morphology can pose a challenge leading to a potential diagnostic error. A variety of benign and malignant diseases, including reactive histiocytic hyperplasia, adenocarcinoma, melanoma, and lymphoma with signet ring cell morphology should be considered in the differential diagnosis. In signet ring cell mesothelioma work up, mucin stains are of limited value. Even though immunohistochemistry is routinely used in mesothelioma diagnosis, there is no sole specific mesothelial marker. Hence, a panel of mesothelial and epithelial markers are used; these should be interpreted with caution especially in this variant. Electron microscopy and genetic testing can be very helpful in distinguishing signet ring cell mesothelioma from its mimickers.

Reactive histiocytic proliferation in the pleural fluid mimicking metastatic signet ring adenocarcinoma

Reactive nodular and diffuse histiocytic proliferations of mesothelial and non-mesothelial lined sites have been sporadically reported in the literature. However, there is no cytologic literature describing this process. We report a case of reactive histiocytic proliferation mimicking a metastatic signet ring adenocarcinoma in pleural fluid from a 33-year-old white male. Ancillary studies such as immunohistochemistry should be used to elucidate the cell of origin and avoid diagnostic errors.

Nodular histiocytic/mesothelial hyperplasia as consequence of chronic mesothelium irritation by subphrenic abscess

PURPOSE

Pleural nodular histiocytic/mesothelial hyperplasia is a nodular histiocytic/mesothelial proliferation, often delimiting cystic cavities, due to irritation by a pulmonary noxa. Case report results: The patient had right pleural parietal and diaphragmatic thickness, with pleural effusion, without lung alterations. He previously underwent left hemicolectomy and liver resection, due to a diverticulitis and a liver histiocytes-rich abscess. Video-assisted thoracoscopy biopsy showed a double population of reactive mesothelial cells and histiocytes.

CONCLUSION

Nodular histiocytic/mesothelial hyperplasia represents a potential pitfall for pathologists. Immunohistochemistry is crucial for the differential diagnosis with some malignancies. We suggest that in our patient, a chronic mesothelium inflammation happened by transdiaphragmatic involvement as a consequence of the liver abscess. Some pathogenetic mechanisms are hypothesized.

Mesothelial/monocytic incidental cardiac excrescence mimicking cardiac tumor

Mesothelial incidental cardiac excrescence is a non-neoplastic tumor-like lesion commonly occurring in the intracardiac region. The exact etiology is unclear. A 32-year-old woman presented with respiratory distress on exertion. Echocardiography showed severe aortic, mitral, and tricuspid regurgitation, for which triple-valve replacement was performed. A small cardiac excrescence was found over the aortic valve, measuring 0.6 × 0.3 × 0.3-cm, which on microscopy showed features of mesothelial/monocytic incidental cardiac excrescence. This condition is very rare but it must be recognized because it mimics a metastatic malignancy.

Polypoid nodular histiocytic hyperplasia associated with endometrioid adenocarcinoma of the endometrium: report of a case

A 45 year old woman underwent Laparoscopy-assisted total hysterectomy with staging procedure following a diagnosis of endometrial endometrioid adenocarcinoma on her endometrial biopsy. The hysterectomy specimen showed a FIGO I stage 1a, endometrioid carcinoma. A separate polypoid lesion in the endometrium, distinct from the carcinoma, was also identified. Microscopically the polypoid lesion was “nodular histiocytic hyperplasia”. The H&E, immunohistochemical staining findings and the differential diagnoses are discussed in this report. Although description of similar lesions is available in the literature, the current lesion is unique as it is identified in a hysterectomy specimen in its entirety and its association with an endometrial endometrioid carcinoma.

A unique case of diffuse histiocytic proliferations mimicking metastatic clear cell carcinoma in the hydrocele sac

Reactive histiocytic proliferations are extremely rare in paratesticular structures. Nodular histiocytic proliferations have been described in mesothelial-lined locations and only at few nonmesothelial sites. Diffuse histiocytic proliferations are described only in the pelvic peritoneum. We report the first case of diffuse histiocytic proliferation in the hydrocele sac of a 45-year-old man. Predominant histiocytes showed clear cytoplasm and signet ring-like change. Mucicarmin stain did not demonstrate mucin in the cytoplasm. Immunohistochemistry (IHC) staining showed nonspecific staining of these cells with carcinoembryonic antigen and negative staining with epithelial membrane antigen, pan-Cytokeratin, calretinin, cytokeratin 7, 20 and prostate-specific antigen. Strong diffuse cytoplasmic positivity for CD68 defined the mononuclear phagocyte nature of these cells. Diffuse histiocytic proliferations can occur in the hydrocele sac. Histochemical and IHC stainings are critical for accurate diagnosis and to avoid unnecessary surgery.

Nodular histiocytic aggregates in the endometrium: a report of 7 cases

Nodular aggregates of nonfoamy histiocytes in the endometrium are uncommon. We describe herein the clinical and pathologic characteristics of 7 additional cases in endometrial biopsies or curettages. The patients ranged in age from 48 to 72 years, and the most common presenting symptom was abnormal uterine bleeding. Five of seven patients had undergone prior endometrial sampling (including 1 who had undergone 3 endometrial biopsies over the preceding 5 yr for follow-up of abnormal uterine bleeding). In 2 cases, an endometrial polyp was present in the same sample, and an additional 2 were found to have endometrial polyps on subsequent biopsies that were performed within 4 months of original samplings. The lesions, which ranged in size from 1 to 8 mm, were composed of monomorphic cells with abundant pink eosinophilic cytoplasm with a vaguely nodular arrangement. Two cases showed focally high mitotic activity with up to 4 mitoses per high-power field. Patient outcomes were unremarkable, which affirms the benign nature of the proliferation. Several features of this lesion, including mitotic activity, focal necrosis, and tight aggregation of cells, may raise the possibility of a neoplastic proliferation. This differential diagnosis can be readily resolved by awareness of the lesion and immunohistochemical analyses. Possible pathogenetic considerations are discussed, but these nodules represent, in our opinion, reaction to necrotic tissue in the endometrial cavity, possibly related to prior procedure.

Lesion of aggregated monocytes and mesothelial cells: mesothelial/monocytic incidental cardiac lesion

A 58-year-old woman with a history of childhood acute rheumatic fever and resultant mitral valve stenosis was admitted to our cardiovascular surgery clinic complaining of tachycardia, dyspnea, and chest pain. After clinical and radiological findings were evaluated, mitral valve replacement, tricuspid De Vega annuloplasty and plication, and resection of giant left atrium were performed. Atrial thrombus was removed from the top of the left atrial wall. Operation material considered as thrombus was sent to a pathology laboratory for histopathological examination. It was diagnosed with mesothelial/monocytic incidental cardiac lesion (cardiac MICE). Microscopic sections revealed that morphological features of the lesion were different from thrombus. The lesion was composed of a cluster of histiocytoid cells with abundant cytoplasm and oval shaped nuclei and epithelial-like cells resembling mesothelial cells within a fibrin network. Epithelial-like cells formed a papillary configuration in the focal areas. Mitotic figures were absent. Here we present a case which was incidentally found in a patient who underwent mitral valve replacement surgery, as a thrombotic lesion on the left atrium wall.

Nodular histiocytic aggregates in the greater omentum of patients with ovarian cancer

Nodular histiocytic aggregate (NHA) of the omentum is a rare benign proliferative process composed predominantly of histiocytes with scattered mesothelial cells. NHA is a differential diagnosis for neoplasms or metastatic tumors in cancer patients. To further clarify this clinical pitfall issue, the authors investigated surgical samples of the greater omentum from 96 patients with gastrointestinal malignancies and 53 patients with gynecologic neoplasms. Visible NHA of greater omentum was identified in 3 patients with ovarian neoplasms (borderline mucinous cystadenoma, low-grade papillary serous cystadenocarcinoma, and juvenile granulosa-cell tumor) but in none of the patients with gastrointestinal malignancies. Similar lesion was also identified on the cell blocks from peritoneal washings in 1 of the 3 patients. Grossly, the lesions formed small yellow-red nodules on the greater omentum, and the NHA lesion was also found diffusely on the surface of the appendix and fallopian tubes in 2 of the 3 patients. Histological study showed that typical NHA changes over an inflammatory background, which may indicate that NHA is a consequence of a chronic inflammatory process of omentum. The predominant infiltration of T lymphocytes in the NHA lesions indicates that the aggregation of histiocytes may be related to the activation of T-cell immunity. This report has first demonstrated visible NHA in the greater omentum of patients with ovarian malignancies, and awareness of this entity should be brought to clinicians to avoid misdiagnosis.

Oncocytic mania: a review of oncocytic lesions throughout the body

Oncocytic lesions are characterized pathologically by an abundance of oncocytes, that is by enlarged, eosinophilic, and finely granular cells enriched in mitochondria. They can arise in numerous organs and tissues, often in endocrine glands, and have been associated with hyperplasia, autoimmunity, and neoplasia. The causes and mechanisms that transform a normal cell into an oncocyte remain to be elucidated. Aim of this article is to review the most common oncocytic lesions, highlighting their key pathological features and clinical significance.

A case of mesothelial/monocytic incidental cardiac excrescence and literature review

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a rare entity which is an amalgam of mesothelial cells, histiocytes, and fibrin, often found occasionally during cardiac valve replacement. We report a case in a 25-year-old Chinese female with serous mitral stenosis and patent foramen ovale. Routine and immunohistochemical stains and ultrastructure examination revealed the vegetation was predominantly composed of histocytes with scattered mesothelial cells. In fact nodular histiocytic/mesothelial hyperplasia (NHMH) is a similar lesion to MICE. MICE and NHMH could be unified, and NHMH may be a better choice.

Paratesticular mesothelioma. Report of a case with comprehensive review of literature

Paratesticular mesotheliomas are rare tumors with 223 cases described so far. The sole plausible causative factor so far ascertained in the pathogenesis of these tumors is asbestos, which however is found in only around 30% to 40% of such cases. The age range of affected individuals is wide, mostly adults and the elderly, but also includes young people and children. The most common presenting symptom is either hydrocele of unknown origin or intrascrotal mass. When hydrocele is the presenting symptom, these tumors are often clinically overlooked and the diagnosis is delayed. Most paratesticular mesotheliomas arise in the tunica vaginalis, but primary tumors of the spermatic cord and epididymis are also on record. Tumors arising from the peritoneal mesothelium of a hernia sac are excluded from this group. The correct diagnosis is almost always made after histologic examination of the operative specimen. Immunohistochemistry and electron microscopy are always helpful and sometimes necessary tools for diagnosis. So far very few cases have been identified or suspected preoperatively on cytologic examination. Three clinicopathologic types of malignant mesotheliomas of the male genital tract are recognized: diffuse tubulo-papillary mesothelioma, well-differentiated papillary mesothelioma, and multicystic mesothelioma. The histologic subtypes are almost always pure epithelial or biphasic. The differential diagnosis is mainly with serous papillary tumors arising from Mullerian vestiges, but several diverse primary or secondary tumors also need to be considered. A clinicopathologic evaluation of a case of tunical diffuse mesothelioma in a 74-year-old male from the AMR Series is the starting point for this general review.

Extrathoracic Mesothelial Proliferations and Their Mimics

Mesothelial proliferations, either reactive or neoplastic in nature, often pose difficult diagnostic dilemmas. Electron microscopy continues to be a gold standard in the identification of mesothelial differentiation. However, it is very common to apply long panels of antibodies for that purpose. In most cases, light microscopy and immunohistochemistry will solve the problem. However, the definitive, specific, and sensitive immunohistochemical marker is still lacking. This is particularly true in peritoneal and testicular mesothelial tumors, in which common embryologic origin with epithelial elements results in overlapping immunohistochemistry and morphology. The particularities of peritoneal and testicular mesothelial proliferations, and the main tumors that may mimic them in these sites, as well as the value and limitations of immunohistochemistry and electron microscopy in their differential diagnosis are the subject of this review.

Mesothelial cells in transbronchial biopsies: a rare complication with a potential for a diagnostic pitfall

The presence of pleural tissue in transbronchial biopsies (TBs) is an incidental finding that has been rarely reported in the literature. It has the potential for causing wrong histologic diagnoses. Clinically, the significance of unintended pleural sampling by bronchoscopy is unknown. TBs containing mesothelial cells from 6 adult patients were studied using immunohistochemical stains. Clinical information was obtained with emphasis on the immediate postbronchoscopy period. The TBs were performed by 6 different bronchoscopists at 4 institutions because of pulmonary infiltrates in 5 patients and a mass lesion in 1 patient. All samples contained lung parenchyma and bronchial wall. They showed clusters of medium to large size polygonal cells with pink to amphophilic dense cytoplasm, round to oval nuclei, and prominent nucleoli. Some of the cells lined stroma and others were detached forming ribbons. They were initially disregarded, interpreted as carcinoma, judged as mesothelial cells, or interpreted as drug-induced reactive epithelial cells. They were positive for cytokeratin and showed nuclear staining for calretinin. They were negative for TTF-1, S100, CEA, and CD68. However, in 1 case, CD-68 positive histiocytes were admixed with enlarged reactive mesothelial cells corresponding to the so-called nodular histiocytic mesothelial hyperplasia. Chest x-ray films performed the same day after bronchoscopy showed no pneumothorax. Incidental sampling of the pleura may occur during the performance of TB and mesothelial cells may mimic carcinoma, pneumocytes, or macrophages. It is important to be aware of the presence of mesothelial cells in clinically uncomplicated TB to avoid an erroneous diagnosis of malignancy.

Sensitivity and specificity of immunohistochemical antibodies used to distinguish between benign and malignant pleural disease: a systematic review of published reports

AIMS

A systematic review of published reports that have evaluated the ability of immunohistochemistry and argyrophil nucleolar organizing region (AgNOR) staining to distinguish between benign and malignant pleural disease.

METHODS

Nineteen relevant papers published during the period 1979-2005 were identified. Individual results of immunohistochemistry for five diagnostic antibodies were extracted to calculate diagnostic sensitivity and specificity. results from five of these studies that had evaluated proliferation markers or AgNOR staining techniques were also summarized.

RESULTS

Most antibodies demonstrated poor to moderate diagnostic ability. Desmin and epithelial membrane antigen (EMA) were the most useful, with sensitivity and specificity both above 74%. The combination of EMA and AgNOR was reported as having 95% diagnostic sensitivity. A high MCM2 labelling index also differentiated between benign and malignant pleural disease.

CONCLUSIONS

Immunohistochemistry is of limited value, but newer diagnostic methods may be useful additions in this area of pathology. The diagnostic importance of histological features seen on plain tissue sections is emphasized as vital for correctly differentiating between benign pleural disease and malignant pleural mesothelioma.

My approach to the diagnosis of mesothelial lesions

Mesothelial lesions pose considerable diagnostic challenges not only because benign tumours, reactive proliferations and malignant mesothelioma can mimic one another, but also because the morphological patterns displayed by malignant mesothelioma can simulate a variety of epithelial and non-epithelial malignancies. Immunohistochemical markers can aid in distinguishing epithelioid malignant mesothelioma from metastatic adenocarcinoma, but because no single marker reliably separates all cases, a panel of stains is recommended. Immunohistochemical studies are of more limited value in sarcomatoid malignant mesothelioma, and other features often play an essential role. The separation of reactive mesothelial proliferations from malignant mesothelioma on small biopsy can be quite difficult, as distinguishing features, such as stromal invasion, often cannot be adequately assessed. In adequately sampled lesions, however, the distinction between malignant mesothelioma, benign mesothelial proliferations and other tumours can be achieved in most cases by using a carefully integrated approach that incorporates clinical and radiographic data, immunohistochemical studies and, in selected cases, histochemical and ultrastructural techniques.

A Case of Mesothelial/Monocytic Cardiac Excrescence Causing Severe Acute Cardiopulmonary Failure

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a benign lesion composed of a haphazard mixture of mesothelial cells, histiocytes, and fibrin, often found incidentally during cardiac valve replacement. Its pathogenesis is controversial with some authors favoring an artifactually produced amalgam while others espoused a reactive phenomenon. Clinically, this entity is important because of potential misdiagnoses as malignancies. We report a case in a 65-year-old man with severe acute aortic regurgitation. A 2.0-cm mobile aortic valve vegetation was documented by transesophageal echocardiography prior to any cardiac instrumentation. At surgery, the lesion was immediately visualized together with free-floating vegetation in the left ventricular outflow tract. Routine and immunohistochemical examination showed a nodule composed of predominantly histiocytes and mesothelial cells, together with fibrin and scattered neutrophils. To our knowledge, this is the first reported case of a mesothelial/monocytic cardiac excrescence causing acute cardiopulmonary failure. The literature on MICE is reviewed with discussion of its etiology.

Nodular histiocytic hyperplasia of the endometrium

We describe the clinical and pathologic features of four cases of nodular histiocytic proliferation in the endometrium. We have been able to find only one brief reference to this lesion in the literature. The lesion in each case was a detached nodule composed of aggregates of histiocytes within a biopsy or curettage specimen. The constituent cells differed from foamy histiocytes of the endometrium in that they had either lobulated or ovoid, vesicular nuclei, distinctive cytoplasmic margins, and a moderate amount of amphophilic cytoplasm. Mitoses were frequent (up to 11 per 10 high-power fields) in one case but were absent in the remaining cases. On immunohistochemical staining, CD68 and lysozyme were strongly expressed in the cytoplasm. Neither estrogen receptor nor progesterone receptor was expressed in contrast to the background endometrium. The cells were also negative for S-100 and cytokeratin. Each patient's postcurettage course was uneventful. The cause of nodular histiocytic proliferation of the endometrium is currently unknown, although response to intracavitary debris has been suggested. The lesion should not be confused with a variety of reactive, inflammatory, or neoplastic conditions, such as xanthogranulomatous endometritis, malakoplakia, histiocytic granuloma, hormonal changes of the endometrial stroma, Langerhans' cell histiocytosis, morular metaplasia, extravillous trophoblast, or exaggerated placental site reaction.

Cytologic clue of so-called nodular histiocytic hyperplasia of the pleura

So-called "nodular histiocytic hyperplasia" (NHH) is a benign histiocytic lesion caused by mechanical irritation, inflammation, and tumor. Frequently, it has been confused with mesothelial lesions and other malignant neoplasms. The diagnostic clue is proliferating cells in the lesion showing diffuse, strong immunoreactivity against the histiocytic marker, CD68. Recently, we encountered a case of so-called NHH of the pleura and confused it with various malignant neoplasms on histologic examination. An 80-yr-old Korean female presented with ascites, pleural effusions, and nodules on the pleural base. Both ascites and pleural effusion tapping smears displayed moderate cellularity, vaguely nodular cellular aggregates mainly composed of mononuclear cells with bland morphology, entrapped mesothelial cells, and background lymphocytes. Pleural biopsy demonstrated vaguely nodular, compact cellular aggregates of reactive histiocytes which were immunoreactive against CD68. Based on our case, cytologic examination as well as immunohistochemical study should be stressed in the case of so-called NHH. They can provide us more credible morphologic clues to reach a more accurate diagnosis than histologic examination alone, and we can avoid invasive procedures or unnecessary therapies to patients. To our best knowledge, this is the first report describing the cytologic features of so-called NHH in the English-language literature.