Keratin and epithelial membrane antigen immunoreactivity in nonneoplastic fibrous pleural lesions: implications for the diagnosis of desmoplastic mesothelioma

Histopathology and enhanced detection of tumor invasion of peritoneal membranes

Tumor invasion of the peritoneal membrane may have an adverse prognostic significance, but its histopathologic features can be diagnostically difficult to recognize. We observed that local peritoneal injury associated with tumor invasion is characterized by activation and proliferation of serosal stromal cells that express cytokeratin, a characteristic property of injured serosal membranes that may have diagnostic utility. To explore this, we examined 120 primary tumors of the gastrointestinal tract and pancreaticobiliary system using cytokeratin and elastic stains to assess for tumor invasion of peritoneal membranes. Peritoneal invasion by tumor was associated with retraction, splaying, and destruction of the elastic lamina and proliferation of keratin-expressing stromal cells of serosal membranes. All 82 peritoneal invasive tumors were characterized by neoplastic cells that invaded the elastic lamina and the serosal connective tissue with neoplastic cells that abutted or were surrounded by keratin-positive stromal cells, whereas all 38 tumors limited to the subserosa showed none of these features. The diagnosis of tumor invasion of peritoneal membranes is enhanced by the combined use of cytokeratin and elastic stains, which in turn would enable better histopathologic correlation with patient treatment and outcome.

Solitary fibrous tumor of the parotid gland: a case report

The solitary fibrous tumor is traditionally associated with a mesothelial-lined surface. However, any organ with mesenchymal tissue has the potential for developing this tumor; therefore, it has been described in organs not associated with serosal surfaces. We report a case of solitary fibrous tumor of the parotid gland. Microscopically, the tumor showed a patternless arrangement of spindle cells in a fibrotic background and prominent vascular structures of varying size. Tumor cells showed a strong immunoreactivity for CD34 and bcl-2 antigens, but the tissue was negative for antibodies directed against actins, S-100 protein, and cytokeratins. One year after excision, the patient was alive and without evidence of disease.

Thoracic solitary fibrous tumor: clinical and pathological diversity

Fourteen cases (13 pleural and one intrapulmonary) of solitary fibrous tumors (SFTs) (the so-called fibrous mesothelioma) were studied. The lesions occurred more in females (nine cases) than males (five cases). The age of patients ranged from 44 to 73 years old (median 60 years). The tumors presented as cough with or without blood-tinged sputum, exertional dyspnea, chest pain, nausea, body weight loss, fever, or as asymptomatic masses detected by routine chest radiograph. Two patients with huge (tumor larger than 20 cm) malignant tumors had accompanying pleural effusion and one associated with hypoglycemia. Ten benign tumors measured 2-11 cm (median size 7 cm) while the remaining four histologically malignant ones measured 20-30 cm in size. All of them were well circumscribed and thinly encapsulated. Hemorrhage and necrosis were more frequently seen in the malignant tumors. Histologically, these lesions were characterized by 'patternless pattern' with occasional hemangiopericytic features (three cases). The tumor cells were all immunoreactive for vimentin, CD 34, and focally actin-positive in one case, but not for keratin, desmin, S-100 protein, carcinoembryonic antigen, alpha 1-ACT and F VIII-related antigen, supported a primitive mesenchymal origin. p53 protein was expressed in two of the malignant cases. Proliferating cell nuclear antigen stain was positive with 50 and 80% of the labeling index in the benign and malignant tumors, respectively, but retinoblastoma gene protein was negative in all tumors. This analysis confirmed the relationship between histological malignant SFTs and tumor size, cellularity, mitotic activity, necrosis and tumor suppressor gene expression. However, the clinical behavior was unpredictable. Complete respectability seemed to be the most important indicator of clinical outcome in the less aggressive tumors.

Expression of muscle actins in diffuse mesotheliomas

Ultrastructural examinations have shown myofibroblastoid differentiation in sarcomatoid/desmoplastic mesotheliomas, but immunohistochemical expression of muscle actins seldom has been documented. We examined 10 sarcomatoid, 12 epithelial, and five biphasic mesotheliomas immunohistochemically for the expression of muscle-specific actin (MSA) and smooth muscle actin (SMA) and compared it with that in 12 specimens of lung cancer. All of the sarcomatoid mesotheliomas were found to be positive for both MSA and SMA. The epithelial cells in nine epithelial and two biphasic mesotheliomas were positive for MSA, but SMA was only positive in one epithelial mesothelioma. Conversely, the lung cancers were negative for both MSA and SMA in the epithelial cells, except for one specimen that was weakly positive for MSA. The stromal cells in both the epithelial mesotheliomas and lung cancers were negative for cytokeratin but were positive for MSA and SMA, whereas the sarcomatoid and biphasic mesothelioma spindle cells were positive for all three antibodies. We concluded that sarcomatoid mesothelioma was positive for MSA and SMA, which is in support of its myofibroblastic differentiation, and that positivity for MSA in some epithelial mesotheliomas might be of diagnostic value in differentiation from lung cancers.

Metastatic prostatic carcinoma presenting as left-sided cervical lymphadenopathy: a series of 11 cases

Eleven cases of metastatic prostatic carcinoma in cervical lymph nodes as a primary presenting sign were identified in a survey of 250 cervical lymph node biopsies from men. The diagnosis was clinically unsuspected in all cases. All occurred on the left side of the neck. These 11 cases represented 11% of all metastatic carcinomas in the neck and 20% of those with left-sided involvement. The diagnosis was readily confirmed by immunostaining for prostate specific antigen and prostate specific acid phosphatase. Six patients are alive and well at an average of 25.8 months and five others survived for an average of 34.4 months, the combined survival being 29.7 months. This contrasts with the dismal fate of patients with metastatic adenocarcinoma from other sites who all died at an average of 2 months from diagnosis. Prostatic carcinoma should always be considered in the differential diagnosis of metastatic carcinoma in cervical lymph nodes in elderly men, as appropriate treatment results in worthwhile prolongation of life.

Desmoplastic malignant mesothelioma: a review of 17 cases

AIMS

To identify the histological features of desmoplastic mesothelioma, and to determine its incidence and prognosis.

METHODS

Two hundred and fifty five cases of malignant mesothelioma were examined over seven years (1982-9) to identify the desmoplastic variant. Sections were cut at 5 microns and stained with haemotoxylin and eosin and with CAM 5.2 (Dakopatts). Asbestos fibre counts were carried out by light microscopy in 14 cases using the potash digestion method.

RESULTS

Seventeen cases were identified as desmoplastic mesothelioma giving an incidence of 6.6%. In 11 cases the cell type in more cellular areas was sarcomatous and in six others it was biphasic. The mean survival time from onset of symptoms to death was 5.8 months for the sarcomatous variant and 6.8 months for the biphasic variant. Twelve of 16 patients had had previous occupational exposure to asbestos, ranging from five months to 43 years. The diagnosis of desmoplastic mesothelioma was only accepted if acellular connective tissue comprised 50% or more of the tumour bulk. Also seen was collagen necrosis, anastomosing bands of often hyalinised collagen with a prominent storiform pattern, and where cellular detail was present there were hyperchromatic nuclei.

CONCLUSIONS

Desmoplastic mesothelioma is a rare variant of malignant mesothelioma with a storiform collagen pattern, collagen necrosis, bland acellular collagen and focal cytological features of malignancy. Though rare, it is important to recognise this variant and distinguish it from a pleural plaque, nonspecific reactive pleural fibrosis, pleurisy, rheumatoid disease, or, rarely, spindle cell sarcomas.

Desmoplastic malignant mesothelioma masquerading as sclerosing mediastinitis: a diagnostic dilemma

A 48-year-old woman presented with dyspnea, chest discomfort, and left vocal cord paralysis that developed 2 months after a flu-like illness. Radiographic examination showed prominence of mediastinal soft tissues and an ill-defined left upper lobe infiltrate. Dense mediastinal sclerosis was found at thoracotomy, and biopsy samples taken from the sclerotic areas showed densely hyalinized fibrotic tissue. Necrotizing granulomas containing organisms resembling Histoplasma capsulatum were present within mediastinal lymph nodes. Based on these findings, a diagnosis of sclerosing mediastinitis was made. During the next year, the patient's respiratory function deteriorated, and biopsy samples taken during a second thoracotomy 1 year later were again interpreted as sclerosing mediastinitis. The patient died postoperatively; at autopsy, the sclerotic mass involving the mediastinum was composed of a mixture of dense fibrosis and sarcomatous tissue. The final diagnosis was localized mediastinal desmoplastic malignant mesothelioma. We report it here because of its unusual clinical presentation, which mimicked sclerosing mediastinitis.

Immunophenotypic heterogeneity in osteosarcomas

Eighteen osteosarcomas were studied immunohistochemically. The tumors were classified into the following six histologic subtypes: five osteoblastic, four chondroblastic, four malignant fibrous histiocytoma-like, two telangiectatic, two low-grade central, and one giant cell-rich. Variable amounts of osteocalcin immunoreactivity were found in all tumors. Factor XIIIa-positive cells, which may be of fibrohistiocytic lineage, were present in three tumors of the malignant fibrous histiocytoma-like type, one of the telangiectatic type, one of the low-grade central type, and the tumor of the giant cell-rich type. One tumor of the osteoblastic type showed cytokeratin and epithelial membrane antigen immunoreactivities. The positive reactions for desmin in four tumors, for alpha-smooth muscle actin in 11 tumors, and for type IV collagen in one tumor seemed to indicate myofibroblastic differentiation of some tumor cells. S-100 protein-positive tumor cells were detected not only in all four tumors of the chondroblastic type, but also in three of the osteoblastic type, one of the low-grade central type, and in the tumor of the giant cell-rich type. These immunohistochemical results suggest that osteosarcomas are composed of heterogeneous cell populations, such as those of the osteoblastic, chondroblastic, myofibroblastic, and fibrohistiocytic types, and occasionally also of cells with epithelial features.

Localized fibrous tumors of the pleura: correlation of histopathological, immunohistochemical and ultrastructural features

The histogenesis of localized fibrous tumor of the pleura (LFTP) is controversial. We studied 12 LFTP's by light microscopy; by immunohistochemical staining for cytokeratin (CK), vimentin, muscle-specific actin, desmin, S-100 protein, epithelial membrane antigen (EMA) and factor VIII; by electron microscopy in 6 tumors; and by lung digestion for asbestos bodies in 4 cases. Three histologic patterns occurred in combination: 1) collagenous, 2) cellular and 3) hypocellular/myxoid. Hemangiopericytoma-like foci were prominent in the cellular areas of 9 tumors. Unusual features included diffuse small cells in 3 tumors, microcystic foci in 2, macrocystic areas in 5 and tumor giant cells in 4 tumors. Neoplastic cells in all patterns stained positively for vimentin and actin in 9 and 4 tumors, respectively, and were negative for all other markers. CK and EMA were identified in mesothelial and epithelial invaginations only. Ultrastructurally, neoplastic cells demonstrated intercellular junctions, intermediate or thin filaments, dense bodies and rough endoplasmic reticulum. Basal lamina was focally present in 5 tumors, while tonofilaments, desmosomes and short microvilli were observed in one case. Our results support the conclusion that LFTP is a neoplasm of the multipotential subserosal cell, and usually expresses mesenchymal (fibroblastic/myofibroblastic) differentiation. Coexpression of mesothelial features is rare. Lung asbestos body quantitation in 4 patients suggests that there is no association between LFTP and asbestos exposure.

Localized fibrous tumor (localized fibrous mesothelioma) of the liver

A case of localized fibrous tumor (LFT) (localized fibrous mesothelioma) of the liver in an 83-year-old woman is presented. The tumor was 15 x 9 x 8 cm and was confined to the left lateral segment of the liver. Occasional mitotic figures (MF) (2 to 3 per 50 high-power fields [HPF]) were present. Strong, diffuse vimentin positivity was demonstrated by immunohistochemistry. Immunoreactivity for cytokeratins (AE1-3), epithelial membrane antigen (EMA), desmin, and desmosomal proteins (desmoplakin I + II) was absent. Electron microscopic examination showed a mesenchymal appearance of the majority of neoplastic cells, with a few ultrastructural features suggestive of mesothelial differentiation. These findings supported a submesothelial origin of the tumor. After a partial hepatectomy with total gross and microscopic removal of the tumor, the patient was alive without recurrence at 2 years, 5 months later. A review of the English literature showed six additional cases that are probably similar. Currently, all tumors have been clinically benign, although follow-up information has been limited.

Pleural mesothelioma of connective tissue type, localized fibrous tumour of the pleura, and reactive submesothelial hyperplasia. An immunohistochemical comparison

Ten diffuse pleural mesotheliomas of connective tissue type have been compared with 14 examples of pleural granulation tissue and 7 localized fibrous tumours of the pleura, using immunohistochemistry to identify cytokeratins of low and high molecular weight and vimentin. Low molecular weight cytokeratin and vimentin were both detected in 8 of the 10 mesotheliomas and in 12 of the 14 reactive lesions. High molecular weight cytokeratin was rarely detected in either lesion. The seven localized fibrous tumours of the pleura were all positive for vimentin and negative for both cytokeratins. These findings support an origin of connective tissue type mesotheliomas from multipotential submesothelial spindle cells and of localized fibrous tumours of the pleura from either conventional fibroblasts or resting submesothelial spindle cells. Antibodies to cytokeratin help distinguish these two neoplasms but provide no assistance in the more difficult diagnostic problem of distinguishing mesotheliomas of connective tissue type from pleural reactions characterized by abundant granulation tissue.

Keratin protein immunoreactivity of sarcomatoid and mixed types of diffuse malignant mesothelioma: an immunoperoxidase study of 30 cases

To define the role of keratin protein immunohistochemistry in the pathologic diagnosis of the sarcomatoid type of diffuse malignant mesothelioma (DMM), we examined 30 DMM (16 pure sarcomatoid type and 14 mixed sarcomatoid-epithelial type) by an indirect immunoperoxidase technique using three commercially available antibodies to keratin proteins. The sarcomatoid (spindle-cell) areas of all 30 cases of sarcomatoid DMM were immunoreactive for keratin proteins. In 14 of 16 cases of sarcomatoid DMM, 50% or more of the tumor cells were reactive with one or more antibodies; however, polyclonal bovine muzzle and monoclonal AE1/AE3 antibodies were distinctly superior to polyclonal human callus keratin antibody in the detection of spindle tumor cells. In contrast with the staining patterns observed for DMM, 39 spindle-cell malignancies and tumor-like processes of 10 histogenetic types were unreactive with the three antibodies. Those spindle-cell tumors and reactive mesothelial proliferations that may enter into the differential diagnosis of sarcomatoid DMM are discussed. We conclude that keratin protein immunohistochemistry is a sensitive and highly useful method for the pathologic diagnosis of the sarcomatoid type of DMM and its distinction from other spindle-cell neoplasms.

Prostatic-type polyps of the lower urinary tract: three histogenetic types?

Seventeen prostatic-type polyps of the lower urinary tract are reported. All occurred in males, and the mean ages of the patients with ureteric orifice, bladder and urethral polyps were 20.5, 60.2 and 36.6 years, respectively. The commonest presentation for the bladder and ureteric orifice polyps was haematuria, whereas that for the urethral polyps was either dysuria or haematuria. The polyps consisted of acini and papillae lined by prostatic-type epithelium, as confirmed by immunostaining for prostatic-specific antigen. Most had interspersed islands or complete covering of transitional epithelium on the surface. We believe that the histogenesis of prostatic-type polyps may differ in the different sites. For the ureteric orifice polyp, the early age of presentation and the simple occurrence of prostatic acini beneath an intact urothelium suggest a developmental abnormality. For the bladder polyp, the late onset of disease and the commonly observed transition with cystitis cystica-glandularis suggest that it may be a metaplastic variant of cystitis cystica-glandularis. On the other hand, the urethral polyp probably represents a hyperplastic lesion, since the prostatic urethra is normally lined partly by prostatic-type epithelium.