CD71 is one of the most useful, but least used antibodies in hematopathology. CD71 is an integral membrane protein, which is involved in the uptake of the transferrin-iron complex. Immunoreactivity is restricted to erythroid precursors with a membranous and cytoplasmic stain pattern.
Previously there have been other erythroid markers, but they have been difficult to interpret because they stain all RBCs and precursors. CD71 stains immature erythroid precursors, which are nucleated, and is not significantly expressed in mature RBCs. The utility of CD71 is to help differentiate between normoblasts and myeloblasts in bone marrow specimens. This is especially powerful when combined with CD34 (sensitive/not specific myeloblast marker) on a dual staining IHC platform (red and DAB chromogens).
CD71 can be a particularly useful tool to help accurately characterize immature cellular elements in bone marrow specimens, and decrease misidentification of normoblasts for myeloblasts and/or ALIP. E-Cadherin will also stain immature erythroid precursors (usually in a dimmer pattern compared to CD71).
Utilization of CD71 in gestational pathology has found it to be helpful to identify nucleated red blood cells (NRBCs) in partial molar pregnancies and spontaneous abortions in contrast to complete moles (absence of NRBCs).
Dim staining is expected in lymphoid cells (significantly different from nucleated red cell precursors), which can serve as a nice control (e.g. tonsil tissue).
Photomicrographs
Lymphoid aggregate with dim CD71 expression (erythroid precursors at the periphery). Can be useful as a control (e.g. tonsil).CD34 (red) and CD71 (brown) double stain in a case of acute myelogenous leukemia (AML).CD71 highlighting erythroid precursors in a normal bone marrow sample.
References
Marsee, D. K., Pinkus, G. S., & Yu, H. (2010). CD71 (transferrin receptor): an effective marker for erythroid precursors in bone marrow biopsy specimens. American Journal of Clinical Pathology, 134(3), 429–435. doi:10.1309/AJCPCRK3MOAOJ6AT
Dong, H. Y., Wilkes, S., & Yang, H. (2011). CD71 is Selectively and Ubiquitously Expressed at High Levels in Erythroid Precursors of All Maturation Stages: A Comparative Immunochemical Study With Glycophorin A and Hemoglobin A. The American journal of surgical pathology, 35(5), 723–732. doi:10.1097/PAS.0b013e31821247a8
Luchini C, Parcesepe P, Nottegar A, Parolini C, Mafficini A, Remo A, et al. CD71 in Gestational Pathology: A Versatile Immunohistochemical Marker With New Possible Applications. Appl Immunohistochem Mol Morphol. 2016;24: 215–220. doi:10.1097/PAI.0000000000000175
Acs G, LiVolsi VA. Loss of membrane expression of E-cadherin in leukemic erythroblasts. Arch Pathol Lab Med. 2001;125: 198–201. doi:10.1043/0003-9985(2001)125<0198:LOMEOE>2.0.CO;2
Sadahira Y, Kanzaki A, Wada H, Yawata Y. Immunohistochemical identification of erythroid precursors in paraffin embedded bone marrow sections: spectrin is a superior marker to glycophorin. J Clin Pathol. 1999;52: 919–921.
CD34 (human hematopoietic progenitor cell antigen) is expressed by endothelial cells and embryonic cells of the hematopoetic system. CD34 is used in a wide variety of ways in diagnostic pathology. It can generally be divided into hematopathology and non-hematopathology uses. As with most situations in diagnostic immunohistochemistry, CD34 is often best used as part of a targeted panel considering the differential diagnosis at hand.
Hematopathology– CD34 will mark myeloblasts and a subset of lymphoblasts. It is therefore not specific for myeloid differentiation (although fairy sensitive). Normal myeloblasts will express CD34, and in cases of AML approximately 70% of cases will be positive. Approximately 1/3rd of cases of ALL may express CD34. It is also important to understand that not all blasts within a specific case may all express CD34, and correlation with flow cytometry data and aspirate count is critical. CD34 also stains vascular endothelium, which makes for a nice internal control in bone marrow biopsies. Granulocytic sarcomas (a.k.a. chloroma, soft tissue AML, or leukemia cutis) often have monocytic differentiation, and only ~5% of case demonstrate CD34 expression.
Non-Hematopathology– CD34 is expressed in cases of dermatofibrosarcoma protuberant (DFSP), hemangiopericytoma, solitary fibrous tumor, angiosarcoma & Kaposi’s sarcoma (>85%), epithelioid sarcoma (often), lymphocyte rich T cell lymphoma, gastrointestinal stromal tumors, and spindle cell lipomas. CD34 is not expressed in dermatofibromas, desmoplastic mesothelioma, & endometrial stromal sarcoma. CD34 is also an excellent vascular marker, which is helpful in identifying lymph-vascular invasion and tumors of vascular origin.
In hepatocellular carcinoma, CD34 highlights increased vascular structures associated with tumorigenesis. Normal liver only shows CD34 expression in portal vasculature and sinusoids immediate adjacent to portal tracts.
Lymphatic & Vascular Invasion – CD34 is sometimes utilized to evaluate for “lymphovascular invasion” (LVI) in different tumors (e.g. breast more commonly). CD34 and CD31 will stain both (blood) vascular endothelium (strong & sensitive) and also lymphatic endothelium (variable & less sensitive). Sometimes CD34 will stain stromal cells, which can mimic endothelium (false positive).
To determine the true nature of LVI (i.e. lymphatic vs. blood vascular invasion) additional markers specific for lymphatic endothelium (podoplanin or D2-40) need to be performed, and comparison made to CD31/CD34 for determination of invasion type:
Gastrointestinal Stromal Tumor (~70%, some smooth muscle neoplasms can express CD34 – up to 10%)
Spindle Cell Lipoma
Epithelioid Sarcoma
Subset of numerous other entities
Photomicrographs
CD34 expression in a case of acute lymphoblastic leukemia/lymphoma (ALL).CD34 expression in a spindle cell lipoma.CD34 expression in a gastrointestinal stromal tumor.CD34 expression in a case of DFSP.CD34 (red) – CD71 (brown) double stain in a case of AML.CD34 highlighting lymphovascular invasion of breast carcinoma.
References
Mohammed RAA, Martin SG, Gill MS, Green AR, Paish EC, Ellis IO. Improved methods of detection of lymphovascular invasion demonstrate that it is the predominant method of vascular invasion in breast cancer and has important clinical consequences. Am J Surg Pathol. 2007;31: 1825–1833. doi:10.1097/PAS.0b013e31806841f6
Yang H, Yu L. Cutaneous and Superficial Soft Tissue CD34(+) Spindle Cell Proliferation. Arch Pathol Lab Med. 2017;141: 1092–1100. doi:10.5858/arpa.2016-0598-RA
Rao N, Colby TV, Falconieri G, Cohen H, Moran CA, Suster S. Intrapulmonary solitary fibrous tumors: clinicopathologic and immunohistochemical study of 24 cases. Am J Surg Pathol. 2013;37: 155–166. doi:10.1097/PAS.0b013e31826a92f5
de Smet D, Trullemans F, Jochmans K, Renmans W, Smet L, Heylen O, et al. Diagnostic Potential of CD34+ Cell Antigen Expression in Myelodysplastic Syndromes. Am J Clin Pathol. 2012;138: 732–743. doi:10.1309/AJCPAGVO27RPTOTV
Rosado FGN, Itani DM, Coffin CM, Cates JM. Utility of immunohistochemical staining with FLI1, D2-40, CD31, and CD34 in the diagnosis of acquired immunodeficiency syndrome-related and non-acquired immunodeficiency syndrome-related Kaposi sarcoma. Arch Pathol Lab Med. 2012;136: 301–304. doi:10.5858/arpa.2011-0213-OA
Patil DT, Rubin BP. Gastrointestinal stromal tumor: advances in diagnosis and management. Arch Pathol Lab Med. 2011;135: 1298–1310. doi:10.5858/arpa.2011-0022-RA
Bénet C, Gomez A, Aguilar C, Delattre C, Vergier B, Beylot-Barry M, et al. Histologic and immunohistologic characterization of skin localization of myeloid disorders: a study of 173 cases. Am J Clin Pathol. 2011;135: 278–290. doi:10.1309/AJCPFMNYCVPDEND0
Dunphy CH, O’Malley DP, Perkins SL, Chang C-C. Analysis of immunohistochemical markers in bone marrow sections to evaluate for myelodysplastic syndromes and acute myeloid leukemias. Appl Immunohistochem Mol Morphol. 2007;15: 154–159. doi:10.1097/PAI.0b013e318030dec7
Dunphy CH, Polski JM, Evans HL, Gardner LJ. Evaluation of bone marrow specimens with acute myelogenous leukemia for CD34, CD15, CD117, and myeloperoxidase. Arch Pathol Lab Med. 2001;125: 1063–1069.
Wang HL, Kim CJ, Koo J, Zhou W, Choi EK, Arcega R, et al. Practical Immunohistochemistry in Neoplastic Pathology of the Gastrointestinal Tract, Liver, Biliary Tract, and Pancreas. Arch Pathol Lab Med. 2017;141: 1155–1180. doi:10.5858/arpa.2016-0489-RA
Wick, MR. “Immunohistochemical approaches to the diagnosis of undifferentiated malignant tumor.”Annals of Diagnostic Pathology12(2008):72-84.
CD31 (PECAM-1) is thought of as a highly sensitive and specific marker for vascular endothelium. It is helpful to identify tumors of vascular origin, and also to identify lympho-vascular invasion by tumors. CD31 may also stain monocytes, megakaryocytic, and granulocytes in addition to endothelial cells. Plasma cells may variably express CD31 (reactive PCs more common). CD31 (like CD34) is more sensitive (and stronger staining) for blood vascular endothelium compared to lymphatic endothelium (less sensitive and variable staining).
Lymphatic & Vascular Invasion
CD31 is sometimes utilized to evaluate for “lymphovascular invasion” (LVI) in different tumors (e.g. breast more commonly). CD34 and CD31 will stain both (blood) vascular endothelium (strong & sensitive) and also lymphatic endothelium (variable & less sensitive). To determine the true nature of LVI (i.e. lymphatic vs. blood vascular invasion) additional markers specific for lymphatic endothelium (podoplanin or D2-40) need to be performed, and comparison made to CD31/CD34 for determination of invasion type:
Kaposi sarcoma is a vascular neoplasm associated with immunodeficiency (usually HIV/AIDS) and is caused by human herpesvirus 8 (HHV-8). Vascular markers (CD31, CD34, D2-40, and FLI1) are helpful (in combination with HHV-8) for diagnosis. CD31 is expressed in 58-75% of cases (strong and diffuse staining). CD34 is considered more sensitive (92%).
Photomicrographs
CD31 highlighting vasculature in a normal section of kidney.
References
Wick, MR. “Immunohistochemical approaches to the diagnosis of undifferentiated malignant tumor.”Annals of Diagnostic Pathology12(2008):72-84.
Vanchinathan V, Mirzamani N, Mizramani N, Kantipudi R, Schwartz EJ, Sundram UN. The vascular marker CD31 also highlights histiocytes and histiocyte-like cells within cutaneous tumors. Am J Clin Pathol. 2015;143: 177–85– quiz 305. doi:10.1309/AJCPRHM8CZH5EMFD
Rosado FGN, Itani DM, Coffin CM, Cates JM. Utility of immunohistochemical staining with FLI1, D2-40, CD31, and CD34 in the diagnosis of acquired immunodeficiency syndrome-related and non-acquired immunodeficiency syndrome-related Kaposi sarcoma. Arch Pathol Lab Med. 2012;136: 301–304. doi:10.5858/arpa.2011-0213-OA
Morgado JMT, Sánchez-Muñoz L, Teodósio CG, Jara-Acevedo M, Álvarez-Twose I, Matito A, et al. Immunophenotyping in systemic mastocytosis diagnosis: ‘CD25 positive’ alone is more informative than the “CD25 and/or CD2” WHO criterion. Mod Pathol. 2012;25: 516–521. doi:10.1038/modpathol.2011.192
Mohammed RAA, Martin SG, Gill MS, Green AR, Paish EC, Ellis IO. Improved methods of detection of lymphovascular invasion demonstrate that it is the predominant method of vascular invasion in breast cancer and has important clinical consequences. Am J Surg Pathol. 2007;31: 1825–1833. doi:10.1097/PAS.0b013e31806841f6
