Diagnostic Immunohistochemistry presents the latest information and most reliable guidance on immunohistological diagnoses in surgical pathology. Dabbs, MD and other leading experts bring you state-of-the-art coverage on genomic and theranostic applications, molecular anatomic pathology, immunocytology, Non-Hodgkin s lymphoma, and more. Additional features such as tables discussing antibody specifications, differential diagnosis boxes, ancillary anatomic molecular diagnostics, and full-color histological images ensure user-friendly coverage that makes key information easy to find and apply. The fully searchable text is also available online at expertconsult.com, along with a downloadable image bank and access to Path Consult.
This concise and complete resource is today s indispensable guide to the effective use of immunohistochemical diagnosis.' .I would recommend as a 'must have' for every pathology department.' Techniques of Immunohistochemistry: Principles, Pitfalls and Standardization2.
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Molecular Anatomic Pathology: Principles, Technique and Application to Immunohistologic Diagnosis3. Immunohistology of Infectious Diseases4. Immunohistology of Neoplasms of Soft Tissue and Bone5.
Immunohistology of Hodgkin Lymphoma6. Immunohistology of Non-Hodgkin Lymphoma7. Immunohistology of Melanocytic Neoplasms8. Immunohistology of Metastatic Carcinoma of Unknown Primary Site9. Immunohistology of Head and Neck Lesions10.
Immunohistology of Endocrine Tumors11. Immunohistology of the Mediastinum12. Immunohistology of Lung and Pleural Neoplasms13. Immunohistology of Skin Tumors14. Immunohistology of the Gastrointestinal Tract15. Immunohistology of the Pancreas and Hepatobiliary Tract16. Immunohistology of the Prostate17.
Immunohistology of the Urinary Bladder, Kidney, and Testis18. Immunohistology of the Female Genital Tract19. Immunohistology of the Breast20. Immunohistology of the Nervous System21. Immunohistology of Pediatric Neoplasms23.
Imaging and Quantitative Immunohistochemistry.
Immunohistochemistry has become an essential ancillary examination for the identification and classification of carcinomas of unknown primary site (CUPs). Over the last decade, the diagnostic accuracy of organ- or tumour-specific immunomarkers and the clinical validation of effective immunohistochemical panels has improved significantly. When dealing with small sample sizes, diagnostic accuracy is crucial, particularly in the current era of targeted molecular and immune-based therapies. Effective systematic use of appropriate immunohistochemical panels enables accurate classification of most of the undifferentiated carcinomas as well as careful preservation of tissues for potential molecular or other ancillary tests. This review discusses the algorithmic approach to the diagnosis of CUPs using CK7 and CK20 staining patterns. It outlines the most frequently used tissue-specific antibodies, provides some pitfalls essential in avoiding potential diagnostic errors and discusses the complementary tools, such as molecular tumour profiling and mutation-specific antibodies, for the improvement of diagnosis and prediction of the treatment response. IntroductionIn the absence of an identifiable primary tumour site, despite extensive multidisciplinary investigations, carcinomas of unknown primary site (CUPs) are characterized as metastatic carcinomas.
Diagnosis is intended essentially to identify the subsets of CUPs sensitive to specific treatment. Beside these clinical entities, the identification of the primary tumour has no prognostic or therapeutic effect and a comprehensive systematic review is unnecessary and costly. However, the therapeutic choice, and several favourable subsets of CUPs, warrants further histopathological characterization, which is often performed with immunohistochemistry (IHC) and, more recently, using molecular analyses ,.
In practice, four primary sites (breast, ovarian, prostate and thyroid) involving specific effective treatment options and a better prognosis should first be investigated. In addition, the development of targeted therapies must eliminate a pulmonary or colorectal origin.IHC provides diagnostic guidance in approximately 90% of undifferentiated malignant tumours but usually at the end of a fastidious and expensive algorithm based on both morphology and IHC.
However, the expression of cytokeratin is not restricted to epithelial neoplasms. Keratin is commonly expressed in some tumours with evidence of epithelial differentiation such as synovial sarcomas, epithelioid sarcomas, desmoplastic small round cell tumours, chordomas, adamantinoma and myoepithelial carcinomas. In addition, aberrant focal expression of cytokeratin has been reported in other tumours including angiosarcomas, epithelioid hemangioendotheliomas, epithelioid leiomyosarcomas and meningiomas, undifferentiated pleomorphic sarcomas, rhabdomyosarcomas, malignant rhabdoid tumours and peripheral nerve sheath tumours, clear cell sarcomas, plasmacytomas, diffuse large B-cell lymphomas, anaplastic large cell lymphomas and melanomas.On the other hand, some tumour-specific antibodies may show a less intense signal or no signal at metastatic sites. The poorly differentiated malignant phenotype can vary but rare positivity is generally weak and focal.
In addition, the intra-tumour heterogeneity can make interpretation more difficult. It is for this reason that IHC using a more or less extensive panel and specificity of antibodies for certain tumour types is necessary in order to precisely determine the origin. In addition to CK7 and CK20 cytokeratins, some of the markers often used routinely are more specific for the primary site.No single antibody is fully sensitive and specific for a particular tumour; however, some antibodies are especially useful when used within small panels. Over the past few years, novel antibodies have been developed, essentially those directed against transcription factors and improved the specificity of diagnosis, when used in combination with other more “classical” antibodies ,.
However, in approximately 5% of cases, IHC may not provide any definitive information and the final diagnosis of an undifferentiated malignant neoplasm is given without any reference to the tumour origin, despite all the investigations.The amount of relevant information required by the clinician to provide optimal and personalized therapeutic support is increasing and transcends the question of the origin of the primary tumour. As of now, platinum-based chemotherapy is the standard management for patients with CUPs. More recently, an alternative strategy offers treatment targeting the assumed primary tumour according to its molecular signature. With this in mind, the randomized phase III trial GEFCAPI04 comparing standard chemotherapy to a chemotherapy regimen tailored to the primary site defined by the gene expression profile is currently recruiting patients in France (clinicalTrials.gov ).Overall, the final diagnosis of CUPs is performed on small-sized samples that are essential to ensure that complementary IHC tests and molecular analyses can be performed without prejudice to the management of the patient. In addition, the myriad of IHC markers required to guide the diagnosis may question their availability and the budgetary impact for each pathology laboratory as well as the potential implementation at a national level of ‘IHC expert centres’ to provide second opinion IHC services.
Tekken 7 game for android 6.0 version. Diagnostic Workflow of CK7+/CK20− CUPsFor CUPs with a CK7+/CK20− pattern, a gastrointestinal origin is diagnosed in 2/3 of cases (50% colorectal, 20% pancreatic, 10% gallbladder, small intestine and rectum). In the 1/3 of remaining cases, more than 50% had an ovarian origin, followed by a lung or breast origin. In only a few cases, it may be difficult to distinguish the primary origin of tumours including mesothelioma.Diagnosis is based on knowledge of the clinical record of the patient, including the clinical oncological history but also the age and sex.
For instance, the search for the expression of hormone receptors is essential for a female patient but is has limited interest for a male patient. Likewise, the expression of WT1 in a female patient can guide the diagnosis either to an ovarian serous carcinoma or malignant mesothelioma; whereas WT1 expression in a male will strongly favour a mesothelioma. Finally, a tumour in an adolescent or young adult is in favour of germ cell, lymphoid, desmoplastic small round cell tumour or Ewing’s sarcoma rather than an ovarian epithelial tumour, for example.The staining pattern for CK7 and CK20 gives an overall indication but has some limitations.
For instance, gastric carcinomas can present a highly variable profile: CK7+/CK20+ in 32% of cases; CK7−/CK20+ in 35% of cases and CK7−/CK20− in 14% of cases. Likewise, ductal and lobular breast carcinomas have a CK7+/CK20− pattern in 86% to 94% of cases but other patterns have been described in a decreasing order of frequency, for example CK7+/CK20+, CK7−/CK20+ and CK7−/CK20−.Once the CK7/CK20 expression profile is established, complementary organ-specific antibodies allow refinement or more precise guidance toward the primary origin of CUPs. However, their reactivity is often complex and they should be used as an integral part of a panel. The most classical antibodies with complex reactivity, used when dealing with a CUP CK7+/CK20− are: TTF1, GATA3, PAX8 and WT1. A lung metastasis of a thyroid carcinoma with a micropapillary component showing ( A) cytoplasmic staining for Napsin A, ( B) negative staining for Thyroglobulin, ( C) diffuse, strong nuclear staining for PAX8 and ( D) strong cytoplasmic staining for BRAFV600E (immunoperoxidase, clone VE1).GATA3 was suggested to identify a breast origin in a tumour expressing CK7+/CK20− and hormone receptors. GATA3 is expressed in 92% to 100% of ductal and lobular breast carcinomas ,.
It exhibits nuclear staining, with most often diffuse and strong reactivity. This staining pattern is observed regardless of the histological subtype (ductal or lobular), the type of sample (biopsy versus surgical resection sample) and the biological phenotype of the tumour (hormone receptor positive or negative and triple negative tumour phenotype). However, GATA3 is also expressed in normal urothelial epithelia and in 80% to 90% of urothelial carcinomas. Mesothelial MarkersCalretininUseful. Positive in 85–100% of MPMs. Positivity in 0–38% of PSPCs prevents its use as a single differential marker.D2-40Potentially useful. Positive in 93–96% of MPMs but also focal positivity in 13–65% of PSPCs; additional data are needed.CK5/6Limited use.
Positive in 53–100% of MPMs but also focal positivity in 22–35% of PSPCs.WT1Not useful. Positive in 43–93% of MPMs and positive in 89–93% of PSPCs.PSPCs MarkersMOC-31Very useful. Positive in 98% of PSPCs and 5% of MPMs.PAX8Very useful. Positive in most Mullerian carcinomas and negative in MPMs.BG8Very useful. Positive in 73% of PSPCs and 3–9% of MPMs.BerEP4Useful.
Positive in 83–100% of PSPCs and in 9–13% of MPMs.B72.3Limited use. Positive in 65–100% of PSPCs and focal expression in 0–3% of MPMs.CEANot useful.
Positive in only 0–45% of PSPCs and negative in MPMs but sensitivity too low compared to other markers.Oestrogen receptorUseful. Positive in 60–93% of PSPCs and 0–8% of MPMs.Progesterone receptorLimited use. Lower sensitivity than oestrogen receptors in PSPCs, negative in MPMs. Can be useful when positive.Mesothelioma vs. Non-Gynaecological Adenocarcinoma (Biliary, Pancreas, Stomach, Colon)CalretininVery useful.
Positive in 85–100% of MPMs but also positive in 10% of pancreatic ADCs, limited value as single marker.WT1Very useful. Positive in 43–93% of MPMs, 3% of gastric ADCs and 0% of pancreatic ADCs.D2-40Potentially useful. Positive in 93–96% of MPMs, negative in gastric and pancreatic ADCs (limited data).CK5/6Not useful. Positive in 53–100% of MPMs and 38% of pancreatic ADCs.MOC-31Very useful. Positive in 5% of MPMs and 87% of ADCs.BG8Very useful.
Positive in 3–9% of MPMs and 89% of ADCs.CEAVery useful. Negative in MPMs and positive in 81% of ADCs.B72.3Very useful. Positive in 0–3% of MPMs, 84% of pancreatic ADCs, 89% of biliary ADCs, 98% colon ADCs.BerEP4Useful.
Positive in 9–13% of MPMs et 98% pancreatic and gastric ADCs.CDX2Useful. Positive in 90–100% of colon ADCs, 80% small intestine ADCs, 70% of gastric ADCs and negative in MPMs. The diagnostic algorithm for workup of a CK7−/CK20+ carcinoma.In these undifferentiated forms, CK20 is often only focally positive, whereas medullary or undifferentiated carcinomas of colorectal origin frequently have a CK7−/CK20− phenotype. In the context of a CK7−/CK20+ CUPs, CDX2 has limited diagnostic value. Actually, CDX2 is not an anatomical marker of the intestine but a transcription factor promoting differentiation and the expression of intestinal specific genes in intestinal cells. It is therefore a low-specific marker for a colorectal origin as it can be expressed in all carcinomas with intestinal differentiation such as adenocarcinoma of the small intestine but also in certain gastric, oesophageal, pancreatic, ovarian, urachal and sinonasal carcinomas.
CDX2 expression may be decreased in right-sided or proximally located colon carcinomas, in poorly differentiated colorectal carcinomas as well as in colorectal carcinomas with microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR).Differential expression of mucins (MUC2, MUC5AC, MUC6, MUC4) that distinguishes the different intestinal origins has been proposed by some authors. However, the frequent association of the expression of several mucins in the same tumour, the difficulty in determining an expression threshold for each of them, as well as the absence of therapeutic impact of the identification of these anatomical origins limits their diagnostic interest. Villin has no added value compared to CDX2 and can also be expressed in numerous non-intestinal carcinomas (bladder, Merkel cell carcinoma, sinonasal intestinal-type adenocarcinoma). On the other hand, the addition of a new marker, the transcription factor SATB2 (special AT-rich sequence-binding protein 2), seems more useful because it would be restricted to the lower gastrointestinal tract. Its expression is maintained in almost all adenocarcinomas of the appendix (including adenocarcinoma ex-goblet cell carcinoid) and in over 85% of colon adenocarcinomas. This increases the predictive value of a colon origin from 93% to 99% for CK7−/CK20+ tumours and is expressed in poorly differentiated colon tumours CDX2− and/or CK20−. Moreover, its expression is preserved in the majority of colorectal medullary carcinomas.It is often difficult but important to distinguish between an adenocarcinoma of the bladder from a colorectal origin because these two tumours have the same morphological appearance and immunohistochemical profile (CK7−/CK20+/CDX2+), while the therapeutic management is different.
The reference treatment for bladder adenocarcinomas is surgical, as these tumours are poorly chemosensitive, unlike colon carcinomas. In addition, the diagnosis of the urachal origin is based on clinical and morphological criteria, while the immunohistochemical profile is most often variable with low specificity, showing similarities to that of extravesical adenocarcinomas. The CK7/CK20 pattern is not very informative in this indication ,.
The CK7+/CK20+ phenotype is observed in approximately 50% of urachal adenocarcinomas, while almost 30% have no CK7 staining and a CK7−/CK20− phenotype can also be observed exceptionally ,. A difference in activation of the Wnt/β-catenin pathway may be useful, resulting in nuclear staining for β-catenin in colorectal carcinomas (75% of cases), while it is mainly expressed in the cell membrane and cytoplasm in bladder adenocarcinomas (17%).Thrombomodulin is expressed in most urothelial carcinomas and in approximately 60% of bladder adenocarcinomas of urachal or non-urachal type. Although positive in numerous other carcinomas, thrombomodulin is negative in digestive adenocarcinomas.
CK34βE12 is expressed in approximately 60% of urachal adenocarcinomas and in only 10% of colorectal adenocarcinomas. Loss of membrane localization and aberrant nuclear E-cadherin expression is often associated with aggressive progression of certain carcinomas, including primary urachal adenocarcinoma. Because it is often lost, or very focally expressed, p63 or p40 are unreliable markers for urachal adenocarcinomas ,.
Diagnostic Immunohistochemistry Dabbs Pdf Merge Pdf
A metastatic urachal adenocarcinoma in the left lung (( A) haematoxylin, eosin and safran) showing patchy staining for ( B) CK34βE12, ( C) CDX2 and ( D) Calretinin but no staining for ( E) p40 and ( F) GATA3 (( B– F) immunoperoxidase).GATA3 is a marker of urothelial differentiation, expressed in 70% to 90% of urothelial carcinomas but is often lost in primary bladder adenocarcinomas , with the exception of signet-ring cell carcinoma of the urinary bladder. It is also expressed in a number of extravesical adenocarcinomas, including breast carcinomas ,. SATB2 is expressed in almost half of the bladder adenocarcinomas, which limits the interest of this antibody in distinguishing between the two origins.The immunohistochemical profile of a CK7−/CK20+ CUPs should include endocrine markers (Chromogranin, Synaptophysin and CD56) as this profile is unique to Merkel cell carcinomas and small cell carcinomas of the salivary glands, both with perinuclear “dot-like” CK20 staining. Therefore, the phenotype of Merkel cell carcinomas is CK7−/CK20+ (“dot-like”), CDX2−, SATB2+, Chromogranin+, Synaptophysin+ and positive for Merkel cell polyomavirus (MCPyV), while the phenotype of small cell carcinomas of the salivary glands is Synaptophin+, Chromogranin+/−, CD56+ and CDX2− ,.MSI-H/dMMR colorectal carcinomas are characterized morphologically by poor differentiation or mucinous secretion and prominent lymphoid stroma but these characteristics are not constant. On the other hand, the morphology of medullary carcinoma is pathognomonic of a dMMR phenotype. The immunohistochemical profile of dMMR colorectal carcinomas can be variable: CK7−/CK20+ but also frequently CK7−/CK20−. They are negative for CDX2 in 15% to 20% of cases.
SATB2 appears to be a more sensitive marker than CDX2 but its expression in the dMMR tumour group is not really known outside medullary carcinomas. Only 5% of metastatic forms of colorectal cancers have a MSI-H/dMMR phenotype. This oncogenic pathway results from the loss of function of the dMMR genes, most often of sporadic origin (80% of cases) by somatic inactivation of the MLH1 gene (hypermethylation of the MLH1 gene promoter), more rarely with genetic harbouring of a deleterious germline mutation in one of the four MMR genes associated with the Lynch syndrome.BRAF gene mutations in MSI-H colorectal cancers are associated with sporadic forms and can be used to rule out the Lynch syndrome. Primary Origin SiteImmunostaining ProfileLung (mucinous) TTF1−/+, CK7−/+, CDX2−/+Pancreas ,Maspin A+, S100P+, IMP-3+, pVHL−, SMAD4−/+, MUC5AC+, CDX2−/+Stomach ,CEA+, CDX2−/+, MUC1−/+, MUC5AC−/+, CDH17+/−, TTF1−Oesophagus ,CEA+, MUC5AC+/−, CDH17+, MUC1−/+, CDX2−/+Ovary (mucinous) ,DPC4+, CA-12.5+, CDX2+/−Urinary bladder ,GATA3+, p63+, p40+, CK5/6+, CK20+/−, S100P+, CK903+, UPIII+/−Small intestine CDX2+, CDH17+, Villin+/−, MUC5AC+/−NUT midline carcinoma ,CK7+/−, CK20+/−, p40+/−, NUT.
Pulmonary metastases have a prevalence of 30% to 50% in patients with extra-thoracic neoplasms. Clinically, the most frequent primitive origins are breast, colon, gastric, pancreatic, renal, melanocytic, prostate, prostate, liver, thyroid, adrenal and genital. The CK7+/CK20+ pattern allows the exclusion of breast (CK7+/CK20−), colon (CK7−/CK20+/−), renal (CK7−/CK20−), prostate (CK7+/CK20−), hepatic (CK7−/CK20−), thyroid (CK7+/CK20−) and adrenal (CK7−/CK20−) origins ,.Mucinous pulmonary adenocarcinomas usually develop in the peripheral regions of the lungs. Several patterns have been described such as lepidic, acinar, papillary, micropapillary, solid and cribriform like in other adenocarcinomas. In general, they are TTF1 negative and can lose the expression of CK7, associated with expression of CK20 and sometimes CDX2. Primary mucinous pulmonary adenocarcinoma (( A) haematoxylin, eosin and safran) showing ( B) no staining for TTF1, ( C) patchy staining for CK7, ( D) strong staining for CK20 and ( E) a few tumour cells stained for CDX2 (( B– E) immunoperoxidase).A KRAS mutation was found in 56% of mucinous adenocarcinomas, while the mutational status correlated neither with the architectural pattern nor with survival of patients. The main differential diagnosis is the metastasis of pancreatic or ovarian origin, with clinical information being essential.The pulmonary intestinal-type of adenocarcinoma is less frequent.
The architecture is cribriform or acinar with tubulo-papillary aspects and may present with focal necrotic points. The cells are usually cylindrical with a brush border and elongated and pleomorphic hyperchromatic nuclei and nuclear crowding. This tumour often mimics a conventional colorectal adenocarcinoma, which is the main differential diagnosis. IHC is not very contributory in this histological TTF1− subtype. Interestingly, TTF1 are rarely expressed in genuine colorectal adenocarcinoma, therefore the clinical information remains paramount.NUT midline carcinomas are very aggressive tumours harbouring rearrangements in the NUT gene that can be detected by IHC using an anti-NUT-specific monoclonal antibody ,.
Although initially described in young subjects, this neoplasm can affect all ages (2–78 years) without gender predominance. This carcinoma does not present any tissue or organ specificity and is morphologically indistinguishable from other poorly differentiated carcinomas originating from midline locations (e.g., epiglottis, sinonasal, lung, mediastinum). The tumours have abrupt areas of squamous differentiation and frequently expresses the p40 protein. NUT midline carcinomas comprise a group of highly aggressive tumours and they are accompanied by distant metastases at the time of diagnosis.The IHC pattern for CK7+, CK20+, GATA3+, p40+ (inconsistent), Villin−, Thrombomodulin+ and the cytoplasmic expression of β-catenin point to a bladder/urothelial origin. Conversely, a Villin+ and Thrombomodulin+ profile combined with nuclear positivity for β-catenin and membrane reactivity to CDH17 are in favour of an adenocarcinoma of the small intestine.The expression of CEA, CA. 125, Dpc4 (SMAD4 family, tumour suppressor gene) or MUC2 but not MUC5AC, would argue in favour of an ovarian metastatic origin.
Moreover, WT1, which are expressed by mesothelial, ovarian (granulosa) and renal glomerular cells, are of interest for CUPs based on the high sensitivity and specificity (90%) in serous carcinomas of the ovary. In addition, Dpc4 is also expressed by normal pancreatic tissue (ducts, acinar cells). A loss of expression is in favour of malignant transformation, which is highly useful for biopsies.
However, while not very specific, this marker has little interest for CUPs as it can also be expressed in the metastases of colorectal, appendix, gastric and endocervical carcinomas.A panel of four markers, associating positivity for Maspin A (mammary serine protease inhibitor), S100P (placental S100 protein), IMP-3 (insulin-like growth factor II messenger RNA binding protein-3) and negativity for pVHL (von Hippel-Lindau tumour suppressor), has 100% sensitivity and specificity for distinguishing high grade dysplasia or malignancy from reactive atypia within the biliary-pancreatic system. In addition, pVHL has added value to distinguish intrahepatic biliary malignancy (cholangiocarcinoma, pVHL positive) from extrahepatic biliary or pancreatic metastasis (pVHL negative).
However, the individual expression of each of these markers does not provide a diagnostic element. For instance, the specificity of S100P is limited as many neoplasms demonstrate positive expression, including pancreatic, gallbladder, digestive, bladder and pulmonary adenocarcinomas. In addition, their routine use is limited by their restricted availability in pathology laboratories. Finally, activating mutations in the KRAS oncogene are likely the single most common genetic abnormality in pancreatic cancer, present in 90–95% of cases. Despite the low specificity, a KRAS gene mutation could provide additional diagnostic criteria.In summary, a diffuse or focal CK7+/CK20+ profile favours a pulmonary (mucinous or intestinal subtypes), pancreatic, gastrointestinal (gastric, oesophageal, small intestine), ovarian (mucinous subtype), bladder or midline carcinoma origin. The absence of a specific marker or the scarcity of certain markers makes clinical information essential, in particular to differentiate a primitive pulmonary origin from a secondary digestive or pancreatic origin. In the absence of clinical information, a prostatic origin may be suspected based on the morphology in the case of well-limited tumour proliferation, arranged in small tubular structures composed of medium-sized uniform cells with prominent nucleoli.
Necrosis, mitosis and vascular invasion are usually rare or absent. The use of anti-PSA and anti-PSAP (prostate-specific acid phosphatase) antibodies allows confirmation of a prostatic origin in most cases. PSA is expressed in normal prostate tissue and in most prostatic adenocarcinomas. However, in high-grade or poorly differentiated carcinomas and in certain histological subtypes such as small cell carcinoma these markers may be negative.
In addition, the loss of PSA expression can be observed in 10% to 20% of metastases and after hormone therapy. Finally, PSA expression has been described in other types of carcinomas such as salivary gland or breast carcinomas. PSAP may be a useful additional marker. It is also expressed in normal prostate tissue and in a majority of prostatic adenocarcinomas.
However, it has a lower specificity than PSA, due to its expression in neuroendocrine tumours (pancreas, digestive carcinoid tumour), urothelial or cloacogenic carcinomas. A metastatic prostatic adenocarcinoma ( A) haematoxylin, eosin and safran) showing ( B) no staining for prostate-specific antigen (PSA) but ( C) diffuse, strong cytoplasmic staining for prostatic specific acid phosphatase (PSAP) (( B, C) immunoperoxidase).Other markers, described as highly specific of a prostate origin, can also be used alone or in combination to determine a prostate origin, such as P501S (prostein), PSAM (prostate-specific antigen membrane) and NKX3.1. Recently, the detection of the ERG protein, which is related to the presence of the fusion gene TMPRSS2-ERG, the most common and specific molecular alteration in prostate cancer, appears to be a complementary diagnostic argument in CUPs, since it is detected in approximately 30% of prostate metastases. Finally, the androgen receptor has a low specificity, as it is expressed in several other tumour types (e.g., breast carcinoma, sebaceous carcinoma) and therefore cannot be used alone to confirm the diagnosis.The CK7−/CK20− profile should also eliminate metastasis from a clear cell renal cell carcinoma. Pulmonary metastases of renal origin are often poorly differentiated or may have different morphological characteristics compared to the primary tumour. A panel of several antibodies associating CK7 and CK20, Vimentin, the RCC marker, CD10 and CAIX most often confirm a renal origin.
PAX8 is a sensitive but not very specific marker, its expression has been observed in carcinomas of renal, thyroid, ovarian, endometrial, or uterine origin. A metastatic renal cell carcinoma (( A) haematoxylin, eosin and safran) showing ( B) diffuse nuclear staining for PAX8, ( C) diffuse, strong cytoplasmic staining for Vimentin but ( D) only a few tumour cells stained for CD10 (( B– D) immunoperoxidase).Finally, useful markers in favour of a hepatocellular carcinoma (HCC) are HepPar-1 and the canalicular markers CD10 or polyclonal CEA.
They are expressed in the majority of HCCs (80%) but sometimes in a heterogeneous way and mostly in well and moderately differentiated HCCs. Arginase-1 is more sensitive (90% of HCCs) and has the advantage of being reactive in poorly differentiated HCCs but may be less available in pathology laboratories. AFP and Glypican-3 are less sensitive but somewhat more specific oncofetal markers (Glypican-3 can be expressed in some melanomas). However, they have the advantage of being expressed in some poorly differentiated HCCs that do not express HepPar-1 or canalicular markers. HCCs express some cytokeratins (CK8, CK18) but pan-cytokeratins are often negative and they do not generally express EMA. Complementary Tools for Diagnosis and Prediction of Treatment Response in CUPsDespite advances in imaging and IHC, CUPs still account for approximately 3% of adult cancers; they are aggressive (medium-average survival. Selected IHC PitfallsAberrant or unexpected antigen expression should be considered as a source of a diagnostic pitfall in the evaluation of undifferentiated tumours.
In general, carcinomas express CK, whereas mesenchymal tumours express vimentin. However, there are carcinomas that show loss of CK expression, carcinomas that frequently co-express vimentin and carcinomas that rarely express both CK and vimentin. In contrast, mesenchymal tumours and hematopoietic neoplasms may express epithelial markers. A pitfall to keep in mind is that poorly fixed specimens may have an unpredictable pattern of staining for CK ,.Non-epithelial tumours with a glandular epithelial component are extremely rare tumours, almost always biphasic, which likely distinguishes them from carcinomas. However, the partial and narrow nature of biopsy samples may sometimes be confined to the epithelial component and may mislead the diagnosis.These biphasic tumours can be classified as “connective” and “non-connective.” The most common biphasic connective tumours are synovial sarcoma, dedifferentiated liposarcoma, mixed tumours/myoepithelioma of soft tissue, malignant peripheral nerve sheath tumour (or MPNST with glandular heterologous differentiation) and hamartomatous ectopic thymoma. Non-connective tumours with a biphasic and/or mixed pattern are mainly represented by biphasic mesotheliomas, germ cell tumours and malignant mixed Mullerian tumours (carcinosarcomas and adenosarcoma with stroma overgrowth).
ConclusionsIn conclusion, in the era of expanding knowledge into tumour genomics and into the immune microenvironment as well as into associated targeted therapy, the role of the pathologist is expanding. A systematic approach, beginning with histomorphological evaluation, the algorithmic application of a small and effective panel of immunomarkers and the precise selection of molecular or other ancillary tests, is required for the efficient management of CUPs. The organ- or tumour-specific immunomarkers, including some newer generations of immunomarkers, help to obtain a specific diagnosis. Only by exercising a systematic approach to working up CUPs can an accurate specific diagnosis be reached.
A systematic approach is also required to preserve tissue for potential molecular or other ancillary testing for most cases in the routine practice.