Indian Journal of Pathology and Microbiology

: 2016  |  Volume : 59  |  Issue : 1  |  Page : 128--129

Cytokeratin-positive interstitial reticulum cells in the lymph node: A potential pitfall

Priya M Jacob, Rekha A Nair, Sindhu P Nair, AV Jayasudha 
 Department of Pathology, Regional Cancer Centre, Trivandrum, Kerala, India

Correspondence Address:
Rekha A Nair
Department of Pathology, Regional Cancer Centre, Trivandrum - 695 011, Kerala

How to cite this article:
Jacob PM, Nair RA, Nair SP, Jayasudha A V. Cytokeratin-positive interstitial reticulum cells in the lymph node: A potential pitfall.Indian J Pathol Microbiol 2016;59:128-129

How to cite this URL:
Jacob PM, Nair RA, Nair SP, Jayasudha A V. Cytokeratin-positive interstitial reticulum cells in the lymph node: A potential pitfall. Indian J Pathol Microbiol [serial online] 2016 [cited 2021 Oct 28 ];59:128-129
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Cytokeratin-positive interstitial reticulum cells (CIRCs) are an infrequent finding seen in lymph nodes with diverse etiologies. They are commonly seen in nodes free of but draining malignant tumors and in Kikuchi's lymphadenitis (necrotizing histiocytic lymphadenitis) and also seen infrequently in nodes showing a range of reactive inflammatory processes, primary, and metastatic neoplasms. CIRC appear to represent a subset of the so-called "fibroblastic reticulum cells" of lymph nodes. Their function remains undetermined; their increase in diverse lymphadenopathies suggests that they partake in nodal reactions to injury. It remains unclear whether the increase in CIRC relative number is due to proliferation or to cytokeratin (CK) gene induction processes, but their presence and potential capability to undergo hyperplasia with dysplastic forms should alert pathologists to possible diagnostic pitfalls. [1]

The following are three cases that depict the spectrum of case studies with incidentally detected CIRCs.

Case 1: Female, 13 years, cervical lymph node with a diagnosis of Kikuchi's lymphadenitis. [Figure 1.1]a and b show CIRC amidst the histiocytes{Figure 1.1}Case 2: Male, 48 years, inguinal lymph node with a diagnosis of Myeloid sarcoma lymph node. The tumor cells were CD33, CD34 and myeloperoxidase positive. [Figure 1.2]a and b show CIRC amidst the tumor cells{Figure 1.2}Case 3: Female, 69 years, radical nephrectomy specimen with a diagnosis of renal cell carcinoma, clear cell type, grade 2 (size 11 cm 10 cm 8.5 cm) with six retroperitoneal lymph nodes showing reactive change. [Figure 1.3]a and b show CIRC within the medullary sinus of a reactive lymph node.{Figure 1.3}

CIRCs were first described by Franke and Moll the year 1987. [2] In a study by Gould et al. where they studied a total of 291 enlarged lymph nodes with diverse etiologies, both neoplastic as well as nonneoplastic, they found that in 258/291 nodes (89%), CIRC numbers were distinctly increased in the subcapsular, paracortical, and, occasionally, in the medullary zones. Often, these increased CIRC formed networks around follicles, sinuses, and vessels. CIRC had comparatively small, irregularly shaped bodies, and dendritic processes; occasionally, giant forms were noted. CIRC contained CK 8 and 18 but not 19, as shown by immunohistochemistry, and by gel electrophoresis with subsequent immunoblotting. They co-expressed vimentin consistently, alpha-smooth-muscle actin frequently, and desmin less frequently. They did not contain desmoplakins, Factor VIII, S-100, leukocyte common antigen, B and T lymphocyte- and macrophage-associated antigens, chromogranin A, synaptophysin, or the A-80 glycoprotein. They found no clear correlation between the increased CIRC and given nodal disease processes. However, CIRC were most abundant in nodes free of but draining malignant tumors; bizarre CIRC assemblies were noted in HIV lymphadenopathy. [1] These CIRC may undergo a transformation and represent the "cell of origin" of certain CK-positive tumors restricted to lymph nodes that remain as unsolved mysteries in the case sheet as metastatic carcinoma with an unknown primary. Altogether, 14 cases of CIRC tumors have been reported in the literature, of which 3 were extranodal. Expression of CK and the very rarely seen extranodal location of these tumors can lead to a misdiagnosis of carcinoma. [3]

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1Gould VE, Bloom KJ, Franke WW, Warren WH, Moll R. Increased numbers of cytokeratin-positive interstitial reticulum cells (CIRC) in reactive, inflammatory and neoplastic lymphadenopathies: Hyperplasia or induced expression? Virchows Arch 1995;425:617-29.
2Franke WW, Moll R. Cytoskeletal components of lymphoid organs. I. Synthesis of cytokeratins 8 and 18 and desmin in subpopulations of extrafollicular reticulum cells of human lymph nodes, tonsils, and spleen. Differentiation 1987;36:145-63.
3Sundersingh S, Majhi U, Krishnamurthy A, Velusami SD. Cytokeratin-positive interstitial reticulum cell sarcoma: Extranodal presentations mimicking carcinoma. Indian J Pathol Microbiol 2013;56:172-5.