Application of electron microscopy in the diagnosis of fine needle aspiration biopsies and tumorous pleural effusion]

Forty-five cases of fine needle aspiration biopsies of tumor and 9 cases of tumorous pleural effusion specimens were reviewed electron microscopically for diagnosis. Among them, electron microscopical diagnosis of 22 cases (40.7%) was valuable, and that of 28 cases (51.8%) was of no diagnostic significance. In 14 out of 22 cases (63.6%) the nature and origin of tumor were further confirmed by electron microscopy, and in 8 cases (36.4%) electron microscopical diagnoses were consistent with light microscopic diagnoses. It was shown that in cytological diagnosis of tumors, electron microscopy was superior to light microscopy in defining the nature and origin of tumors, and in differentiating neuroendocrine tumors, leukemia and small round cell tumors.     

Metachronous soft-tissue masses in children and young adults with cancer: correlation of histology and aspiration cytology

We describe a series of 28 fine needle aspiration biopsies (FNAB) of soft tissue from 22 patients. Four patients had two separate FNABs, and one had three aspiration procedures. The patient population was limited to children and young adults (age range, 2 months to 29 years; mean, 16 years) who were known to have diverse forms of cancer, and who subsequently developed a mass in the peripheral soft tissues (including breast). The interval between the time of diagnosis of the primary malignant neoplasm and FNAB ranged from 1 day to 17 years (mean, 39 months). All FNAB diagnoses were confirmed by subsequent surgical open biopsy or clinical follow-up greater than 1 year. No complications occurred from the procedure. The cytomorphology is presented in selected cases and correlated with the patient's original tissue histopathology. Twenty aspirates were diagnosed as cytologically malignant, one as suspicious for malignancy. Seven were considered benign. None were unsatisfactory. One false-positive and no false-negative cytologic diagnoses were obtained. The overall accuracy of FNAB diagnoses was 96%, while sensitivity was 100% and specificity 88%. Sites of aspiration included soft tissues of the head and neck (seven cases), trunk (eight cases), breast (four cases), and extremities (nine cases). Malignant cytologic diagnoses included sarcoma (thirteen), seminoma (two), lymphoma/leukemia (two), melanoma (one), undifferentiated neoplasm (one), and neuroblastoma (one). Electron microscopy of aspirated cells was used to confirm the diagnosis in two cases. Fine needle aspiration biopsy of soft tissue masses from children and young adults with cancer demonstrates a high diagnostic accuracy, and its use is justified in this population.     

Light and electron microscopic examination of fine-needle aspirates in the preoperative diagnosis of cartilaginous tumors

Twenty-eight patients with chondrogenic tumours--2 chondroblastomas, 4 chondromas, 18 chondrosarcomas, 1 clear-cell chondrosarcoma, and 3 mesenchymal chondrosarcomas--underwent fine-needle aspiration biopsy (FNAB) in the preoperative investigation. The cytologic features in smears were compared with the histopathologic findings in the surgical specimens; in 14 cases they were also compared with the light and electron microscopic findings in resin-embedded fine-needle aspirates. The smears of the vast majority of the classical chondrosarcomas presented features that made possible the FNAB diagnosis of a chondrogenic tumor to be made. In the case of the low-grade chondrosarcomas in particular, which were poorly or moderately cellular in smears and showed chondroblastic cells often in lacunary structures of hyaline matrix, consideration of the clinical presentation, size, location, and roentgenographic appearance was essential for the diagnosis of chondrosarcoma. On the other hand, the high-grade chondrosarcomas presented cytologic features that clearly indicated their malignancy and they usually had a myxoid matrix. The possible differential diagnoses that may arise from the FNAB diagnosis of cartilaginous tumors are discussed. The resin-embedding technique for the light and electron microscopic examination of FNABs, along with the histochemical analysis for the demonstration of sulphated glucosaminoglycans and the immunocytochemistry applied to smears, was found to be of value in the definite diagnosis, especially in the distinction of chondrogenic tumors from chordoma and metastatic mucous-producing carcinoma.     

The accuracy of fine-needle aspiration cytology in the diagnosis of canine skin and subcutaneous masses

A retrospective evaluation of cytologic and histopathologic specimens from 300 cutaneous and subcutaneous palpable lesions in dogs was performed. Preoperatively, specimens were obtained from each formation by fine-needle aspiration biopsy (FNAB). Samples for histopathology were obtained by surgical excision biopsy or at necropsy. The concordance and the accuracy of FNAB for the diagnosis of neoplasia were determined using histopathology as a gold standard. Fifty-two cases were considered as unsatisfactory and were excluded from the study (retrieval rate 82.66%, n = 248). Neoplasia was diagnosed in 193 cytologic specimens. In 190 cases, neoplasia was confirmed by histology (98.44% true positive). Fifty-five cytologic specimens were classified as non-neoplastic. In 35 (63.63%) cases, the cytologic diagnoses were in agreement with the histologic diagnosis (true negative), while in 20 (36.37%) cases, a false negative diagnosis of neoplasia was made by cytologic examination. Based on the results from our study, there was 88.7% (220/248) agreement between cytologic and histologic diagnoses. In diagnosing neoplasia cytology had a sensitivity of 90.47%, a specificity of 97.22%, a positive predictive value of 98.44%, and a negative predictive value of 63.63%.     

Accuracy of fine needle aspiration biopsy processed by cytologic smear and cell block techniques for the diagnosis of lacrimal gland tumors: a study of 48 cases

Objective: To study the accuracy of fine needle aspiration biopsy (FNAB) processed by smear cytology and cell block (CB) techniques for the diagnosis of lacrimal gland tumors (LGTs). Study Design: In a prospective study, we enrolled 48 consecutive patients with LGTs. Immediately after excision of LGTs, the tissues were underwent FNAB with 23-gauge needles. The FNAB samples were processed to produce cytologic smears and CB from which slides were cut for immunohistochemical staining. The remainders were submitted for routine histopathologic processing. The diagnostic value of FNAB was assessed by comparing the FNAB diagnoses to those made by routine histopathology. Results: Cytopathologic evaluations based on smear cytology and CB with sections stained immunohistochemically can distinguish non-epithelial lesions from epithelial ones in all cases. The diagnostic sensitivities, specificities, and accuracies for distinguishing benign from malignant lesions were: cytologic smears--76%, 68%, and 71%, respectively; CB with immunohistochemical staining--88%, 87%, and 88%, respectively. The accuracy of the tissue diagnosis compared to routine histopathology was less for cytologic smears (58%) than for CB with immunohistochemistry (81%; P < 0.05). Conclusions: FNAB of LGT processed using a CB technique capable of producing immunohistochemically stained slides results in a greater percentage of accurate tissue diagnoses than do cytologic smears, when compared to routine histopathology.     

The value of fine needle aspiration biopsy in the diagnosis and prognostic assessment of palpable breast lesions

In recent years there appears to be a growing movement toward the use of core needle biopsy (CNB) over fine needle aspiration biopsy (FNAB) for the detection of breast carcinoma. This tendency is caused in part by the idea that CNB can provide a more specific or definitive diagnosis as well as the belief that the assessment of prognostic/predictive factor is not possible or reliable on cytologic specimens. At our institution, FNAB of breast has been practiced for over 25 years with excellent cytologic-histological correlation. This practice has been beneficial not only for patients, but also for training physicians since nowadays a very small number of centers in the United States still routinely perform fine needle aspiration as a diagnostic tool in breast cases. To assess the diagnostic accuracy of FNAB in palpable breast lesions, we reviewed our experience during an 8-year-period and compared fine needle aspiration results with follow-up surgical specimens. From the cytology point of view, the lesions were divided as negative/benign, atypical/suspicious, positive, and insufficient. Only cases performed by pathologists were included. A total of 1,583 cases were retrieved from our archives. A definitive malignant diagnosis was reached in 357 cases. One-hundred and thirty-nine cases were classified as atypical/ suspicious, 135 cases had insufficient cells for establishing a diagnosis, and 952 were categorized as negative. A total of 408 follow-up surgical specimens were available for comparison with cytologic results. There were 19 false-negative, and no false-positive results were found. The majority of false-negative results were secondary to sampling errors. In 93% of the malignant cases, there was enough material obtained in cytological specimens to perform prognostic/predictive factors studies. Our data proves once again that FNAB is a reliable method for the initial evaluation and diagnosis of palpable masses of the breast. In addition, it also has the ability of providing necessary prognostic/predictive information, particularly for patients that may undergo neoadjuvant therapy.     

Diagnostic accuracy of image-guided percutaneous fine needle aspiration biopsy of the mediastinum

Interpreting a fine needle aspiration biopsy (FNAB) from the mediastinum is challenging as this location may harbor many lesions, including primary and metastatic tumors. Image-guided transthoracic (percutaneous) FNAB is less invasive than mediastinoscopy or endoscopic-guided FNAB. The aim of this study was to determine the diagnostic accuracy of FNAB performed percutaneously for evaluating mediastinal lesions.A retrospective study of 157 consecutive CT-guided transthoracic FNAB of the mediastinum was performed (1988-2004). Direct smears (N = 145; average 13 slides/case), ThinPrep slides (N = 25), and adequate cell blocks (N = 131) were prepared from procured cytologic material. When needed, ancillary studies included immunocytochemistry (N = 53) and flow cytometry (N = 8). Subsequent histologic tissue diagnoses available for 68 cases were also reviewed.Patients were of average age 57 yr (range 1-88 yr), including 75 males and 82 females. A definitive diagnosis was rendered in 128 (82%) cases. Primary neoplasms (N = 38) included 24 lymphomas (6 Hodgkin and 18 non-Hodgkin), 7 thymomas, 1 thymic carcinoma, and 6 peripheral nerve sheath tumors. Metastases (N = 72) were mainly carcinomas (N = 71) and 1 melanoma. There were 4 non-neoplastic lesions (1 granulomatous process; 2 bronchogenic and 1 pericardial cyst), 1 case of undifferentiated malignant large cell neoplasm, 13 cases negative for malignancy, and 29 (18%) that were indeterminate, due largely to insufficient cellularity. Subsequent histologic diagnoses were concordant with FNAB diagnoses in 53/68 cases (78%). Nine FNAB were inadequate/nondiagnostic. There were 6 discordant cases, including 5 FNAB that were of adequate cellularity but interpreted as negative for malignant cells (on subsequent histology 2 turned out to be Hodgkin lymphoma, 2 carcinomas, and 1 diffuse large cell lymphoma), and 1 diagnosed as thymoma that on histologic evaluation was a thymic large cell lymphoma.Adequate diagnostic cytologic material was obtained by image-guided percutaneous FNAB of mediastinal lesions in 82% of our cases. Sufficient material was available to make cell blocks and perform ancillary studies when necessary. These data also show a high proportion of agreement (78%) between FNAB and subsequent histologic diagnoses for a wide variety of mediastinal lesions. The majority of discordant cases were primarily interpretive, with a final cytologic diagnosis negative for malignancy. Only one problematic case misdiagnosed on FNAB as thymoma was found on subsequent surgical excision to be a thymic large B cell lymphoma. Cases with nondefinitive FNAB diagnoses were largely due to sampling error and/or insufficient cellularity. Therefore, percutaneous FNAB of the mediastinum is a diagnostically helpful, minimally invasive procedure that can be performed in patients of all ages as part of the evaluation of a mediastinal mass lesion.     

Fine needle aspiration in the diagnosis of liver neoplasms: a review

Fine needle aspiration biopsy (FNAB) for the diagnosis of liver neoplasms is a safe, rapid, and accurate technique. It is most useful in patients with a hepatic mass(es) and a previously diagnosed malignant neoplasm. With the current application of immunocytochemical techniques, accurate cytologic diagnoses can be made in most primary and secondary hepatic neoplasms. The equipment necessary to perform FNAB is simple, inexpensive, and readily available. The principle of this technique is to obtain a representative cellular aspirate via a small bore needle and produce a stained image on a microscopic slide that reflects the disease process in the patients. Techniques and clinical skills of FNAB and experiences of interpretation are required to make maximal use of this diagnostic modality.     

Reliability of fine-needle aspiration biopsy in the initial diagnosis of soft-tissue lesions

We retrospectively reviewed fine-needle aspiration biopsy (FNAB) specimens of 301 soft tissue lesions of the extremities and trunk. Final diagnoses were 137 benign and 86 malignant neoplasms and 78 nonneoplastic lesions. Of the 301 FNAB samples, 279 (93%) were adequate for cytologic diagnosis. The adequate FNAB specimens were initially grouped into three broad categories: benign (197 cases), malignant (57 cases), and suspicious for malignancy (25 cases). Sensitivity and specificity for diagnosis of a malignant lesion were 92% and 97%, respectively. The specimens were cytomorphologically classified into nine categories: small round (14 cases), spindle cell (77 cases), epithelioid/polygonal (16 cases), pleomorphic (29 cases), myxoid (19 cases), lipomatous (37 cases), epithelial (23 cases), inflammatory lesions (28 cases), and others (36 cases). Specific FNAB diagnoses were correct in 151 of 279 cases (54%) in combination with clinical and radiologic findings. FNAB is a valuable technique for the primary diagnosis of soft-tissue lesions.     

Value of electron microscopy in diagnosis of renal disease.

AIMS--To assess the role and value of electron microscopy in the diagnosis of renal disease. METHODS--Retrospective evaluation of 88 renal biopsy specimens received for primary diagnosis by assessment of the contribution of electron microscopy to the final diagnosis in the knowledge of the light microscopy and immunofluorescence findings. RESULTS--Electron microscopy had an important diagnostic role in 75% of cases and was essential or necessary for diagnosis in 25%. In 25% of cases electron microscopy was considered unhelpful in diagnosis. CONCLUSION--Electron microscopy has an integral role in the diagnosis of renal disease, and tissue should be taken for electron microscopy in all cases if possible. In some selected cases once the light microscopy and immunofluorescence findings are known it may be possible to forego electron microscopic examination. Electron microscopy is particularly useful in the differential diagnosis of minimal change disease and the nephrotic syndrome.     

Correlation of thyroid nodule fine-needle aspiration cytology with corresponding histology at Mayo Clinic, 2001-2007: an institutional experience of 1,945 cases

Following the National Cancer Institute Thyroid Fine Needle Aspiration State of the Science Conference, the thyroid fine‐needle aspiration biopsy (FNAB) practice at Mayo Clinic, Rochester, Minnesota, conducted retrospective analyses correlating cytologic and histologic evaluations of thyroid nodules. Cytologic and histologic reports were retrieved for patients with thyroid nodules who underwent thyroid FNAB between January 2001 and December 2007, with subsequent surgical thyroid resection. Cases were classified by major cytologic and histologic diagnosis and specific diagnostic subcategories. Of 1,945 FNAB cytologic results, 180 (9.3%) were nondiagnostic; 512 (26.3%) were negative for malignancy; 27 (1.4%) were atypical; 729 (37.5%) were suspicious for malignancy; and 497 (25.6%) were positive for malignancy. Histology was benign in 1,179 (60.6%) and malignant in 766 (39.4%). For thyroid malignancy as the disease outcome, at cytologic thresholds of atypical, suspicious, and positive, overall sensitivity of thyroid FNAB was 94.5%, 94.1%, and 65.0%, respectively, and specificity was 46.0%, 48.3%, and 98.5%, respectively. Positive predictive value for all malignancies was 97.0%, and negative predictive value was 92.0%. When separated by specific malignant outcomes, diagnoses of papillary carcinoma, medullary carcinoma, and lymphoma had specificity of suspicious FNAB diagnoses ranging from 90.5% to 99.6%; positive predictive value ranged from 87.5% to 91.4%. For follicular or Hürthle carcinoma, suspicious FNAB diagnoses had a specificity of 52.5% and a positive predictive value of 5.9%. Sensitivity of indeterminate FNAB diagnoses ranged from 72.7% to 95.3%. For follicular or Hürthle pattern malignancies, indeterminate cytologic diagnoses should be interpreted with caution by the clinician considering surgical management. Diagn. Cytopathol. 2012;40:E27–E32. © 2010 Wiley Periodicals, Inc.     

The use of electron microscopy to refine diagnoses in the daily practice of cytopathology

Conceived as a screening tool, cytology is a field that since the 1980s has become more diagnostic in its scope. The advent of the fine-needle aspiration biopsy (FNAB) is responsible for cytology's new place in pathology. In the everyday practice of cytopathology, about 85-90% of the nongynecologic cases can be diagnosed with the use of routine stains (i.e., Papanicolaou and Diff Quik). The other 10-15% of the cases require the use of ancillary diagnostic techniques for a precise diagnosis. Immunohistochemistry helps solve approximately 50% of these cases, and the other half of these challenging cases are best approached and diagnosed by using electron microscopy (EM). In their practice, the authors obtain cytologic samples for EM routinely in difficult cases. Unfortunately, a percentage of these cases collected for ultrastructural evaluation do not have enough cells after processing, and others only have a few diagnostic cells available. In the cases in which at least a handful of cells are available, EM is almost invariably helpful in one way or another, either making a definitive diagnosis or refining the diagnosis. A sampling of FNAB cases from the authors' everyday practice is prevented to illustrate the use of EM in the practice of cytopathology. The cases have been selected from among the most common diagnostic challenges to highlight the important role that ultrastructural evaluation plays in a busy cytology practice. In our practice ultrastructural evaluation is a piece of the puzzle, which, along with the clinical history, clinical impression, light microscopic/cytologic features, and other ancillary techniques (IHC, flow cytometry, and molecular pathology), help compile an accurate diagnosis. Many times EM is the most important component of the diagnostic algorithm.     

Cytologic features of clear cell sarcoma (malignant melanoma) of soft parts: a study of fine-needle aspirates and exfoliative specimens

We describe the cytologic features of clear cell sarcoma of soft tissue (CCS) in 11 fine-needle aspiration biopsy (FNAB) specimens and 6 exfoliative specimens from 11 patients. In 3 patients, FNAB was the initial method of tumor evaluation. In 6 of 11 cases, immunostaining with S-100 or HMB-45 was evaluated. Electron microscopic evaluation was performed in 1 case. Both the FNAB and exfoliative specimens varied in overall cellularity, although reproducible cytologic features were identified. A significant diagnostic pitfall, namely the potential of CCS to form microacinar structures mimicking adenocarcinoma, is described with particular reference to CCS metastatic to regional lymph nodes. A rare case of the granular cell variant of CCS is illustrated as well. Owing to the rarity of CCS, the diagnosis on cytologic smears is extremely difficult and is aided substantially by pertinent clinical data. The diagnosis can be made conclusively by     

Transthoracic fine-needle aspiration vs concurrent core needle biopsy in diagnosis of intrathoracic lesions: a retrospective comparison of diagnostic accuracy

To assess the value and limitations of fine-needle aspiration (FNA) and core needle biopsy (CNB) in the diagnosis of intrathoracic lesions, we retrospectively compared the diagnostic accuracy of 362 FNA and concurrent CNB procedures performed on 350 patients. Based on the final diagnoses that were determined based on combined information from biopsy, resection, clinical, radiologic, and microbiologic findings, the study cases were grouped into 188 malignant, 161 benign, and 13 inconclusive lesions. FNA and CNB yielded similar diagnostic accuracy for malignant tumors (85.1% vs 86.7%) and epithelial malignant neoplasms (86.4% vs 85.2%), whereas CNB yielded better diagnostic accuracy (96%) than FNA (77%) for nonepithelial malignant neoplasms. Combined FNA and CNB substantially improved the rate of malignancy diagnosis (95.2%). Of 161 benign cases, 50 were proven to be benign-specific lesions; FNA provided specific diagnosis in 20 (40%) and CNB in 46 (92%). The remaining 111 benign lesions yielded benign-nonspecific findings on both specimens. These results indicate that CNB should be obtained when clinical or radiologic findings do not match the cytologic findings or nonepithelial lesions and benign lesions are considered likely.     

Use of fine-needle aspiration biopsy in the evaluation of splenic lesions in a cancer center

Fine-needle aspiration biopsy (FNAB) of the spleen was performed on 50 patients, of whom 40 had had a previous diagnosis of malignancy (23 lymphoproliferative disorders, 13 carcinomas, 3 melanomas, and 1 sarcoma). The cytologic diagnoses included 22 cases positive for malignancy (10 lymphomas, 9 metastatic carcinomas, 2 metastatic melanomas, and 1 sarcoma), 18 cases negative for malignancy, 4 cases suspicious for malignancy, and 6 nondiagnostic specimens. No major complications were associated with the FNAB procedure; however, one patient did develop a pneumothorax that resolved spontaneously. Subsequent splenectomy was performed in 10 of the 50 cases. There were no false-positive diagnoses, and only one false-negative diagnosis, which was attributed to sampling error. The aspirate, showing only benign splenic parenchyma, was from a patient with splenomegaly and no previous diagnosis; subsequent splenectomy showed acute myelogenous leukemia. In our study, FNAB proved to be a safe and valuable diagnostic tool for evaluating splenic lesions in oncologic patients. Diagn. Cytopathol. 16:312–316, 1997. © 1997 Wiley-Liss, Inc.     

Fine-needle aspiration cytology of hemangiopericytoma: report of two cases

The fine-needle aspiration biopsy (FNAB) findings in two cases of hemangiopericytoma (HP), arising in the parotid gland and on the inner chest wall, respectively, are reported. Smear preparations in each case showed cytologic features of an undifferentiated spindle-cell neoplasm, whereas a core needle biopsy specimen of the chest wall mass showed a spindle-cell tumor with a "staghorn-like" arrangement of endothelium-lined vascular channels. Immunostains performed on this core biopsy, and on the surgical resection specimens in both cases, showed positive staining of tumor cells for vimentin and CD34, with negative staining for a variety of smooth muscle, epithelial, neural, and neuroendocrine markers. Electron microscopy performed in one case further supported the diagnosis of HP. With adequate sampling and appropriate use of ancillary studies, a diagnosis of HP can be reliably suggested on the basis of FNAB and core biopsy of a soft-tissue mass.     

Rinse fluid and imprint smear cytology of bronchial biopsies in diagnosis of lung tumors

The usefulness of rinse fluid and imprint smear cytology of the bronchial biopsy has been studied in diagnosis of lung cancer. However, scarce data is available regarding rinse fluid cytology of biopsy. The aim of this study was to evaluate these cytologic techniques for their diagnostic accuracy. Bronchial biopsy was taken in 52 patients clinically/radiologically suspected to have lung carcinoma. Imprint smears of the biopsy were prepared, following which it was put in balanced saline solution to collect rinse fluid of biopsy before transferring it to formalin for fixation. Cytological diagnosis from imprint and rinse fluid smears was compared with histopathological diagnosis. Malignancy was detected in 45 cases of 52 patients on histopathology. Positive result was given by rinse fluid cytology in 34 (65.4%) cases while diagnostic accuracy was 78.8%. The imprint smears were positive for malignancy in 44 (84.6%) cases with diagnostic accuracy of 98.08%. There were no false-positive results, but one case was incorrectly typed by both the techniques. Imprint smear cytology has a better diagnostic accuracy and efficacy over rinse fluid while the two cytologic techniques can be used in combination routinely with biopsy to provide an early and reliable diagnosis in lung cancer.     

Fine-needle aspiration biopsy of orbital and periorbital masses

We present the cytologic findings of 18 fine-needle aspirates performed on orbital and periorbital masses. An accurate specific diagnosis was confirmed by histology in ten cases. In eight cases the diagnostic evaluation and/or therapeutic regimen was significantly altered by the results of the fine-needle biopsy. In three cases the cytologic diagnoses obviated the need for open biopsy. Two specimens were insufficient for diagnosis. No false positive diagnosis of malignancy occurred. Electron microscopy was useful in three cases to confirm the correct cytologic diagnosis. Immunocytochemistry helped to define a lymphoid proliferation as monoclonal. The cytologic findings from an unusual case of sebaceous carcinoma are presented.     

The use of electron microscopy for the diagnosis of cancer in bronchial biopsies

To investigate whether electron microscopic examination of bronchial biopsy specimens was of any additional value in the diagnosis of lung cancer, we examined 235 consecutive biopsy specimens embedded in Epon. Semithin sections were used to establish a light microscopic diagnosis, and the results were compared with those of electron microscopy. Ninety-six biopsies contained tumor. In 13 instances, the light microscopic diagnosis had to be revised after electron microscopic examination. Another 5 biopsies contained tissue suspected to be tumor; in 1 biopsy this possibility could be ruled out. Three biopsies contained tumor suspected of being small cell cancer, and this diagnosis was confirmed by electron microscopy. Electron microscopy was helpful in 17 of 106 biopsies. Histopathologic examination of surgically resected material from 18 patients confirmed the electron microscopic results of biopsies. We conclude that electron microscopy of bronchial biopsy specimens gives important additional information for accurate diagnosis. For practical purposes, however, specimens should be embedded in Epon or glycol-methacrylate for light microscopy. Developments in immunohistologic techniques will change choices of histologic techniques.     

Immunohistochemistry in the differential diagnosis of tumours of possible myogenic origin.

A series of 34 cases of soft tissue tumours of possible muscle origin was studied immunohistochemically using different antibodies. Tissue specimens and/or aspirates from fine needle aspiration biopsy (FNAB) were examined. The results indicate that immunohistochemistry is a valuable tool in differential diagnosis of soft tissue tumours, improving diagnostic accuracy in 83.5% of the examined cases. Desmin expression confirmed muscle differentiation of tumours in 47.6% of diagnostically difficult cases. The application of immunohistochemistry may be especially helpful in rendering the diagnosis of tumour type more precise when a needle aspirate is the only available diagnostic material.