Diagnosing tumours on routine surgical sections by immunohistochemistry: use of cytokeratin, common leucocyte, and other markers

Our plain-English summary of Diagnosing tumours on routine surgical sections by immunohistochemistry: use of cytokeratin, common leucocyte, and other markers, by R.N. Poston, Y.S. Sidhu (Journal of Clinical Pathology, 1986).

The study

• Authors: R.N. Poston, Y.S. Sidhu
• Journal: Journal of Clinical Pathology
• Published: 1986;39(5):514-23
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Tumours of uncertain tissue of origin were investigated by immunohistochemistry on formalin fixed paraffin embedded sections. Two antibodies--PD7/26, an anti common leucocyte antigen, and CAM5.2, an anticytokeratin--recognised most lymphomas and carcinomas, respectively: 88% of these tumours were identified by the two antibodies alone. These antibodies permitted the separation of the cases into groups: positive with CAM5.2, positive with PD7/26, and a third comprising those negative with both. The negative group contained other tumours and a small number of carcinomas and lymphomas; many of the lymphomas were, apparently, of histiocytic origin. Comparison of CAM5.2 with other epithelial markers showed that it was the most effective. Some further classification of the tumours was carried out with a panel of organ and cell specific antibodies: mesotheliomas were recognised by their pattern of reactivity with epithelial markers. Overall, the tumour type was determined in 90% of cases. Immunohistochemistry performed as described can be a potent aid to the diagnostic histopathology of tumours.

In plain English

This study tested antibody stains on routine paraffin-embedded surgical sections that pathologists at Guys, Lewisham, and New Cross hospitals had found hard to diagnose. It focused on 88 tumours of uncertain tissue of origin, mainly anaplastic. Two antibodies were used first: CAM5.2, marking cytokeratins in carcinomas, and PD7/26, marking leucocytes in lymphomas. These two alone led to a diagnosis of carcinoma or lymphoma in 60% of the 88 tumours. After the full panel of markers, a definite diagnosis of origin was made in 90% of the 88 tumours. Among carcinomas, CAM5.2 was positive in 51 of 57, more often than the other epithelial markers tested. Twelve tumours were referred to tell mesothelioma from carcinoma, and eight were finally diagnosed as mesothelioma. All eight were positive with CAM5.2 and LP34 and negative for CEA, a pattern absent in 14 carcinomas tested. The article does not mention asbestos or say where the mesotheliomas arose. The authors concluded that immunohistochemistry has a role in diagnosing such tumours. They said more extensive studies were needed to assess how specific the mesothelioma pattern is.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory diagnostic study (case series) of referred surgical specimens tested with immunohistochemistry
• Who was studied: Surgical specimens that remained hard to diagnose after conventional histology, referred from Guys, Lewisham, and New Cross hospitals. The main group was 88 tumours of uncertain tissue of origin, mainly anaplastic. Other groups were 53 carcinomas of uncertain organ of origin (including mesothelioma versus carcinoma), 31 lymphomas of uncertain cell type, and 13 benign-or-malignant problems.
• Exposure: Not applicable. No asbestos or other exposure was studied. The study tested antibody markers, chiefly CAM5.2 (cytokeratin) and PD7/26 (common leucocyte antigen), plus LP34, HMFG2, CEA and other panel antibodies.
• Main results:
  • Among the 88 tumours of uncertain tissue of origin, a definite diagnosis of origin was made in 90% of cases after use of the full marker panel. Origin could not be determined in 9 of the 88.
  • In the 88-tumour group, 60% were diagnosed as carcinoma or lymphoma using CAM5.2 and PD7/26 alone.
  • In tumours finally diagnosed as carcinomas, positivity was: CAM5.2 51/57 (89%), HMFG2 39/59 (66%), LP34 13/24 (54%) and CEA 16/30 (57%).
  • Of 12 tumours referred to distinguish mesothelioma from carcinoma, all reacted with CAM5.2, and CEA staining was negative in nine.
  • Eight tumours were finally diagnosed as mesothelioma, by histology and markers combined. LP34 staining was strong in all but one. By the table, these mesotheliomas were CAM5.2 positive 8/8, LP34 positive 8/8, HMFG2 positive 3/7 and CEA positive 0/8.
  • The pattern of CAM5.2 positive, LP34 positive and CEA negative was absent in 14 carcinomas tested with these markers. It was found in two histologically unclassifiable tumours in which mesothelioma was part of the differential diagnosis.
  • Comparing initial histological opinion with the immunohistochemical diagnosis in the 88 tumours: 50 (57%) were concordant and 11 (13%) were discordant. In 19 (22%) there was no histological diagnosis, and in 9 (10%) there was no immunohistochemical diagnosis.
• The authors' conclusion: The authors concluded that immunohistochemistry has an important role in diagnosing anaplastic tumours that conventional histology cannot assign to a tissue of origin. They concluded that screening with CAM5.2 and PD7/26 is a straightforward first step. They suggested that strong LP34 and CAM5.2 staining with negative CEA may be of diagnostic use for mesotheliomas.
• Limitations the authors state:
  • The indirect immunoperoxidase technique used is less sensitive than more complex techniques and may occasionally give false negative results.
  • More extensive studies are needed to assess how specific the mesothelioma staining pattern is.
  • The panel gave only limited evidence of the organ of origin of carcinomas. More organ specific markers are needed.
  • The case mix reflects which material hospitals and pathologists chose to refer.

Topics

Medical terms in this study, explained in our Lexicon: Immunohistochemistry, CAM5.2, Carcinoma, Mesothelioma, Histopathology.

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