Immunohistochemistry Case Examples
Allen M. Gown
Anthony S.Y. Leong
Section 4 -
Three Case Histories Illustrating the Diagnostic Value of Immunohistochemistry in Histologically Difficult Neoplasms
Department of Pathology, School of Medicine
A 65 year old male presented with a mass in the left parotid region which had been slowly growing to a
size of 3 cm over a period of 3-4 months. He was otherwise well. The mass on imaging studies appeared
to be a lymph node adjacent to the parotid gland which otherwise looked normal. The lymph node was
excised and submitted for review with a suspected diagnosis of granulomatous inflammation, but T-cell
lymphoma could not be excluded.
On low power the lymph node showed effaced architecture with a nodular infiltrate and prominent
fibrosis. There were areas of necrosis within a polymorphous infiltrate composed of lymphocytes, plasma
cells and eosinophils. Scattered giant cells were noted together with some atypical RS-like cells in a
histiocyte-rich background. Most of the infiltrate was positive for CD45 including some larger cells,
but with very scanty presence of CD20+ cells. Most of the infiltrate was of T-cell phenotype with some
of the larger cells appearing to be positive for CD4 but there was no expression of CD30 or CD15. Large
numbers of histiocytes were noted, with positivity associated with some of the plump epithelioid cells.
Diagnosis of a peripheral T-cell lymphoma was suspected, but PCR analysis indicated polyclonal patterns
of amplification with both T and B-cell primers.
A search for tumour of non-lymphoid origin was therefore conducted. Pan cytokeratin stain was
performed and identified large scattered atypical blasts. These were shown on in situ hybridisation to
be positive for EBER. The diagnosis of "lymphoepithelioma-like carcinoma was made" (undifferentiated
carcinoma of nasopharyngeal type). The patient's pharynx was investigated and biopsied. One of the
blind biopsies of the pharynx showed an inflammatory infiltrate. On closer inspection there were
recognised to be scattered atypical blasts positive for AE1/AE3 and also strongly positive for EBER.
This type of tumour is very commonly initially diagnosed as a metastasis and is often initially
misdiagnosed as lymphoma, and indicates the value of the combined availability of a wide panel of
immunohistochemical markers and PCR and in situ hybridisation techniques in a specialist laboratory
A 61 man presented with an irregular prostate on per rectum examination. The serum PSA was not
raised. The prostate biopsy was shown to be negative for PSA and prostate specific acid phosphatase
(PSAP). Histologically the tumour could not be diagnosed to be of bladder origin. Application of
34betaE12 showed it to be however diffusely strongly positive for this pan keratin marker supporting the
diagnosis of a tumour of urothelial origin. Cystoscopy showed a tumour mass growing out of the bladder
mucosa. Biopsy of this tumour showed it to be of urothelial origin on histological grounds. The use of
a panel of PSA, PSAP and 34betaE12 can be helpful for differentiation of a urothelial tumour from a
histologically ambiguous PSA-/PSAP- tumour infiltrating the prostate.
( Varma M, Morgan M, Amin MB, Wozniak S, Jasani B. High molecular weight
cytokeratin antibody (clone 34betaE12): a sensitive marker for differentiation of high-grade invasive
urothelial carcinoma from prostate cancer. Histopathology. 2003;42:167-72)
A 58 year old man was admitted as an emergency with a one day history of haematemesis and melaena. He
underwent an emergency laparotomy for a tumour in the lesser curve of the stomach. The tumour showed
histological features which were difficult to interpret and needed immunohistochemical investigation to
definitively diagnose it to be an epithelioid haemangioendothelioma. Surgery in the form of wide
excision was conducted as the treatment of choice for this rare neoplasm. Vascular tumours of the
stomach are rare, representing 0.9%-3.3% of all gastric neoplasms. This case highlights the difficulty
in diagnosing this type of tumour preoperatively and emphasises the need for long term follow up in view
of its uncertain metastatic potential.
(Sanjay P, Raman S, Shannon J, Williams GT,
Woodward. A gastric epithelioid haemangioendothelioma: a rare cause of upper gastrointestinal
bleeding. Postgrad Med J.