New Use of Antibodies // Can NKX3.1 Be Used for Differential Diagnosis of Mesenchymal Chondrosarcoma?

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6 2 月, 2026

On 6 2 月, 2026

Introduction:

As is well known, NKX3.1 is a highly sensitive and specific marker for prostate cancer. The loss of NKX3.1 is an indicator for androgen-independent prostate cancer and tumor invasion/metastasis. Literature reports that NKX3.1 is expressed in small amounts in sarcomas. According to published transcriptome data, NKX3.1 mRNA expression is upregulated in EWSR1-NFATC2 sarcoma, and some scholars have proposed NKX3.1 as a new marker for mesenchymal chondrosarcoma. In light of this, the editor came across a recent article published in “Annals of Diagnostic Pathology” where Madiha S et al. investigated the expression of NKX3.1 in mesenchymal chondrosarcoma, aiming to explore the diagnostic value of NKX3.1 in mesenchymal chondrosarcoma.

Research Background

NKX3.1, also known as NKX3A, belongs to the homeobox gene family, located at 8p21.6, with two exons. The second exon contains the homeobox sequence, encoding a 234-amino acid homeodomain protein. As an important class of transcriptional regulators, it regulates the expression of structural genes in a trans-acting manner, determining the body’s morphology and internal organ structure during embryonic development by controlling the development and differentiation of different cell types. Historical studies have shown that NKX3.1 is predominantly expressed in prostate tissue, and its loss of expression can lead to the occurrence of prostate cancer. Therefore, NKX3.1 is a highly sensitive and specific marker for prostate cancer.

Mesenchymal chondrosarcoma is a rare subtype of chondrosarcoma. The tumor exhibits a typical biphasic pattern, with areas of poorly differentiated small round cell components and well-differentiated hyaline cartilage islands. The histological diagnosis of mesenchymal chondrosarcoma is very challenging, especially in small biopsies where the tumor shows minimal cartilage components. In such cases, it is difficult to distinguish mesenchymal chondrosarcoma from other round blue cell tumors, such as Ewing sarcoma, rhabdomyosarcoma, small cell osteosarcoma, and desmoplastic small round blue cell tumor. Immunohistochemical staining of mesenchymal chondrosarcoma shows positivity for NKX2.2, CD99, S100, and SOX9. However, this set of immunohistochemical markers is non-specific and overlaps with other round blue cell tumors. To date, there is no reliable immunohistochemical marker for distinguishing mesenchymal chondrosarcoma from other round blue cell tumors.

Research Content

This study selected 21 cases of mesenchymal chondrosarcoma and 32 cases of other round blue cell tumors (13 cases of Ewing sarcoma, 13 cases of alveolar rhabdomyosarcoma, and 6 cases of desmoplastic small round blue cell tumor). Sections were subjected to HE and NKX3.1 immunohistochemical staining. Microscopic observation: staining intensity was graded as weak, moderate, or strong; staining extent was categorized as negative (0% or <5% positive cells), focal (5%-50% positive cells), and diffuse (>50% positive cells).

Research Results

Among the 21 cases of mesenchymal chondrosarcoma, 14 cases (66.7%) were positive for NKX3.1, with nuclear expression in the small round cell components, while the cartilage components were mostly negative. All other small round blue cell tumors were negative (Table 1, Figure 1).

Table 1. Statistical Table of Staining Results

D,diffuse；F,focal；M,moderate；S,strong；W,weak；

Figure 1. HE staining of mesenchymal chondrosarcoma (A1 and A2) and NKX3.1 IHC staining showing diffuse positivity (B1) and focal positivity (B2).

In another study by Yoshida et al., NKX3.1 immunohistochemical staining was performed on 179 sarcoma cases. The results showed that all 12 cases of mesenchymal chondrosarcoma were positive, with more than half showing diffuse staining of moderate or strong intensity. Positive staining was only observed in the primitive small round cell components, while the cartilage components were mostly negative. EWSR1-NFATC2 sarcoma showed positivity in 9/11 (82%) cases. Other round blue cell tumors were all negative. (Not elaborated here; pleaserefer to the original article for details).

Summary

Based on the two articles, NKX3.1 has certain practical value in the differential diagnosis of mesenchymal chondrosarcoma. Can it be used as a new diagnostic marker for mesenchymal chondrosarcoma? The editor believes the sample size is relatively small, and further research is needed. In clinical practice, when NKX3.1 is positive, attention should be paid to distinguishing between mesenchymal chondrosarcoma and EWSR1-NFATC2 sarcoma.

Related Antibodies from Maixin

Antibody Name	Product Number	Clone Number	Positive Localization
^NKX3.1	RMA-0753	EP356	Nuclear

References:

[1] Madiha S, Sajid M, Asif L, et al. NKX3.1 a useful marker for mesenchymal chondrosarcoma: An immunohisto-chemical study[J]. Annals of Diagnostic Pathology, 2020.10

[2] Yoshida K I , Machado I , Motoi T , et al. NKX3-1 Is a Useful Immunohistochemical Marker of EWSR1-NFATC2 Sarcoma and Mesenchymal Chondrosarcoma[J]. American Journal of Surgical Pathology, 2020:1.

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