Pan-TRK positive uterine sarcoma in immunohistochemistry without neurotrophic tyrosine receptor kinase gene fusions: A case report

Abstract

BACKGROUND

The classification of uterine sarcomas is based on distinctive morphological and immunophenotypic characteristics, increasingly supported by molecular genetic diagnostics. Data on neurotrophic tyrosine receptor kinase (NTRK) gene fusion-positive uterine sarcoma, potentially aggressive and morphologically similar to fibrosarcoma, are limited due to its recent recognition. Pan-TRK immunohistochemistry (IHC) analysis serves as an effective screening tool with high sensitivity and specificity for NTRK-fusion malignancies.

CASE SUMMARY

We report a case of a malignant mesenchymal tumor originating from the uterine cervix, which was pan-TRK IHC-positive but lacked NTRK gene fusions, accompanied by a brief literature review. A 55-year-old woman presented to the emergency department with abdominal pain and distension, exhibiting significant ascites and multiple solid pelvic masses. Pelvic examination revealed a tumor encompassing the uterine cervix, extending to the vagina and uterine corpus. A punch biopsy of the cervix indicated NTRK sarcoma with positive immunochemical pan-TRK stain. However, subsequent next generation sequencing revealed no NTRK gene fusion, leading to a diagnosis of poorly differentiated, advanced-stage sarcoma.

CONCLUSION

The clinical significance of NTRK gene fusion lies in potential treatment with TRK inhibitors for positive sarcomas. Identifying such rare tumors is crucial due to the potential applicability of tropomyosin receptor kinase inhibitor treatment.

Key Words: Uterine sarcoma; Cervical sarcoma; Neurotrophic tyrosine receptor kinase gene fusion; Next generation sequencing; Case report

Core Tip: This case report highlights a rare malignant mesenchymal tumor originating from the uterine cervix that was pan-TRK immunohistochemistry-positive but lacked neurotrophic tyrosine receptor kinase (NTRK) gene fusions. Although NTRK-fusion sarcomas are aggressive and may benefit from targeted TRK inhibitor therapy, this case underscores the importance of molecular genetic diagnostics to guide accurate treatment decisions. The report contributes to the limited literature on NTRK-positive uterine sarcomas and emphasizes the potential clinical value of TRK inhibitors in selected cases.

INTRODUCTION

Sarcoma of uterine cervix is very less common histological type of cervical cancer. This, information regarding the incidence and characteristics of sarcoma of the cervix is based on smaller case series. In a hospital-based tumor registry, 8 cervical sarcomas were identified among 1583 cervical malignancies[1]. Treatment of such rare cervical tumors is not currently included in the National Comprehensive Cancer Network Guidelines for cervical cancer and current treatment strategies may be extrapolated from data regarding uterine sarcomas and soft tissue sarcomas.

The classification of cervical sarcomas is based on distinctive morphological and immunophenotypic characteristics, increasingly supported by molecular genetic diagnostics[2]. Neurotrophic tyrosine receptor kinase (NTRK) fusion-positive uterine sarcoma is a recently recognized mesenchymal tumor that is defined by its morphologic resemblance to soft tissue fibrosarcoma[3]. Pan-TRK immunohistochemistry (IHC) analysis serves as an effective screening tool with high sensitivity and specificity for NTRK-fusion malignancies. The clinical significance of NTRK gene fusion lies in the potential treatment with TRK inhibitors for positive sarcomas. We report a case of a malignant mesenchymal tumor originating from the uterine cervix, which was pan-TRK IHC-positive but lacked NTRK gene fusions.

CASE PRESENTATION

Chief complaints

A 55-year-old woman (gravida 1, para 1) was admitted to the emergency department with the chief complaints of progressive abdominal distension and dyspnea.

History of present illness

Her symptoms, which had developed over the preceding 2 weeks, were accompanied by a body mass index of 19 and an unremarkable medical history.

History of past illness

No significant past history or any illness or surgery.

Personal and family history

No relevant family history contributed to the current condition.

Physical examination

Pelvic examination revealed a tumor engulfing the uterine cervix and extensively invading the vagina and uterine corpus. Colposcopy indicated abnormal vasculature and necrotic change in the cervical mass, with heavy bleeding upon touching. A cervical punch biopsy was performed during the colposcopy (Figure 1).

Figure 1  Colposcopic images of the cervical mass from the patient.

Laboratory examinations

The patient initially underwent tests for CA125, HE4, and SCC, with results of 30.4 U/mL, 29.4 pmol/mL, and 0.66 ng/mL, respectively, all within normal ranges. For follow-up tests, only SCC was measured, and it remained within the normal range, below 1 ng/mL, during chemotherapy.

Imaging examinations

Computed tomography (CT) of the abdomen and pelvis showed significant ascites and multiple ill-defined lesions along the pelvic peritoneum, including a 6 cm mass in the pelvic cavity, initially suspected to be ovarian in origin. However, laboratory tests did not reveal any specific findings to confirm this. Consequently, ovarian cancer with peritoneal carcinomatosis was considered as a preliminary diagnosis, necessitating further imaging for clarification.

Magnetic resonance imaging (MRI) of the pelvis revealed a 4.5 cm infiltrative mass in the cervix, significant hematocolpos, and parametrial invasion. Pronounced adenomyosis was observed in the posterior uterine wall. Diffuse hemoperitoneum and peritoneal thickening, suggestive of peritoneal seeding, were also noted (Figure 2A). A Subsequent positron emission tomography-CT (PET-CT) scan showed a large hypermetabolic cervical mass (SUVmax: 9.8) invading the upper-mid-vagina and uterine corpus, with extensive central necrosis. This scan also revealed right sided hydronephroureterosis and multiple hypermetabolic lesions in the right pelvis and paracolic gutter (Figure 2B), leading to a diagnosis of advanced cervical cancer.

Figure 2 Imaging at diagnosis. A: Pelvic and chest computed tomography; B: Pelvic magnetic resonance imaging; C: Positron emission tomography-computed tomography. A 5 cm mass with necrosis in the uterine cervix is observed (arrows, yellow), along with multiple peritoneal seeding in the right paracolic gutter (arrows, orange) and a large amount of ascites. T2WI: T2 weighted image; T1WI: T1 weighted image; DWI: Diffusion weighted image; ADC: Apparent diffusion coefficient.

FINAL DIAGNOSIS

Liquid-based cytology detected ovoid to round cells with hyperchromatic nuclei. IHC exhibited diffuse strong positivity for pan-TRK (Figure 3). The cervical punch biopsy yielded infiltrating tumor cells arranged in a sheet pattern, displaying vesicular nuclei and distinct nucleoli. Mitotic activity was commonly observed as well as some necrotic areas. As in the cytology specimen, pan-TRK staining was positive (Figure 4). Subsequent next-generation sequencing (NGS), the sole method available at our institution to detect NTRK gene fusion, did not identify any relevant variants, including NTRK gene fusion.

Figure 3 Liquid-based cytology detected ovoid to round cells with hyperchromatic nuclei. Immunohistochemistry exhibited diffuse strong positivity for pan-TRK. A and B: Low power view of uterine cervix (A) (Papanicoalu stain, × 40) A cluster of atypical cells with clumped chromatin is observed, and some cells with low cohesion are scattered individually (B) (Papanicoalu stain, × 100); C and D: The tumor cells were ovoid to round cells with hyperchromatic nuclei formed loosely cohesive clusters without keratinization (C) (Papanicoalu stain, × 400). Pan-TRK staining showed diffuse strong positivity in cytologic specimen (D) (× 400).

Figure 4 Pan-TRK staining was positive. A and B: Infiltrating tumor cells in a sheet pattern were observed in cervical biopsy (A) [hematoxylin-eosin (HE) stain, × 40]. Round or oval cells have a vesicular nucleus and distinct nucleoli. Mitotic activities were commonly observed and there were also some necrotic areas (arrow) (B) (HE stain, × 400); C: As in the cytology specimen, pan-TRK staining was positive (× 200).

TREATMENT

Consequently, combination chemotherapy was chosen as the first-line treatment. The patient was started on a regimen of mesna, doxorubicin, ifosfamide, and dacarbazine (MAID).

OUTCOME AND FOLLOW-UP

After six cycles of MAID chemotherapy, a follow-up pelvic CT was performed to assess the treatment response. The 5 cm cervical tumor observed in the pre-treatment images had completely disappeared after chemotherapy, and the ascites had also resolved. Most of the multiple peritoneal seeding observed in the right paracolic gutter, which measured up to 4 cm, had improved, leaving only small peritoneal seeding less than 1 cm (Figure 5). The patient is currently undergoing concurrent chemoradiation with cisplatin as second-line treatment.

Figure 5 Post-chemotherapy imaging. A follow-up pelvic computed tomography showed substantial improvement with only minimal residual peritoneal seeding remaining (arrow).

DISCUSSION

NTRK gene fusions, first identified in colon carcinoma in 1982[4], have gain significant attention in oncology, particularly in sarcoma research. Notably, infantile fibrosarcoma demonstrates NTRK gene fusion in over 90% of the cases[5]. These fusions are characterized as ‘druggable’ alterations, responsive to TRK inhibitors regardless of the tumor’s tissue of origin.

Recent advancements in tumor-agnostic therapies, particularly TRK inhibitors, have shown promising efficacy and safety. The oncologic outcomes of TRK inhibitors in previous studies are presented in Table 1. Most studies have not focused solely on the uterine cervix but have utilized TRK inhibitors across various organs with NTRK gene fusion, evaluating the efficacy based on the NTRK status. Larotrectinib, a pioneering ATP-competitive small-molecule TRK inhibitor, demonstrated significant effectiveness in TRK fusion cancers across various age groups and tumor types in a combined analysis of three phase I/II trials[6]. An integrated analysis involving 159 patients revealed an objective response rate (ORR) of 79% [95% confidence interval (CI): 72% to 85%], median response duration of 35.2 months (median follow-up 12.9 months), and a median time to response of 1.8 months[7]. Larotrectinib’s favorable safety profile, combined with its clinical efficacy, has translated into substantial, sustained improvements in the quality of life[8].

Table 1 Oncologic outcomes of TRK inhibitors in NTRK gene fusion positive tumors.

Ref.	TRKi	Sample size	Tumor type	Objective response rate (%)	Duration of response (months)	Progression free survival (months)	Overall survival (months)
Demetri et al[9]	Entrectinib	121	Sarcoma, salivary, NSCLC, etc.	61.2	20 (95%CI: 13.0-38.2)	13.8 (95%CI: 23.4-46.4)	33.8 (95%CI: 23.4-46.4)
	Entrectinib	26	Sarcoma	57.7	15.0 (95%CI: 4.6-NE)	10.1 (95%CI: 6.3-13.7)	18.7 (95%CI: 14.5-NE)
Drilon[10]	Larotrectinib	122	Salivary, infantile fibrosarcoma, thyroid cancer, lung cancer, etc.	81	Not reached	Not reached	Not reached
	Entrectinib	54	Sarcoma, lung cancer, mammary analogue secretory carcinoma, etc.	58	10.4	11.2	20.9
Suh et al[11]	Larotrectinib	23	Soft tissue sarcoma	52.2		Not reached	Not reached
	Entrectinib	16	Soft tissue sarcoma	56.3		10.1	16.8
Demetri et al[12]	Larotrectinib	71	Sarcoma, salivary, NSCLC, etc.	87 (95%CI: 77-94)	Not reached	28.3 (95%CI: 16.8-NE)	44.4 (95%CI: 44.4-NE)
	Entrectinib	13	Sarcoma, NSCLC, salivary, breast, thyroid	46 (95%CI: 19-75)	10.3 (95%CI: 4.6-15.0)	11.0 (95%CI: 6.5-15.7)	16.8 (95%CI: 10.6-20.9)

TRKi: Tyrosine receptor kinase inhibitor; NSCLC: Non-small cell lung cancer; CI: Confidence interval; NE: Non-estimable.

Entrectinib, a multi-targeted, inhibitor active against pan-TRK, c-ros oncogene 1 (ROS1), and anaplastic lymphoma kinase (ALK), has similarly shown tumor-agnostic efficacy. An integrated analysis from phase I/II trials reported and independently assessed an ORR of 57% (95%CI: 43% to 71%) and a median response duration of 10.4 months (median follow-up 12.9 months)[13]. Notably, treatment-naïve patients demonstrated higher response rates than those who had received prior systemic therapy. Entrectinib led to a higher response rate in treatment-naïve patients with metastatic disease (n = 30/37; ORR = 81.1%) vs those who had received more than 1 line of prior systemic therapy (n = 44/84; ORR = 52.4%)[9].

The detection of NTRK gene fusion is crucial, as it influences the consideration of TRK inhibitors in management strategies for patients with confirmed NTRK gene rearrangement. However, the rarity of NTRK fusions in sarcomas necessitates reliable diagnostic tools and strategies. Techniques such as IHC, fluorescent in situ hybridization (FISH), reverse transcription polymerase chain reaction, and NGS vary in sensitivity, specificity, and turnaround time (Table 2). Pan-TRK IHC is advantageous due to its high sensitivity, specificity, and cost-effectiveness, making it a practical screening tool. However, it is not definitive for determining treatment plans[14]. FISH, while sensitive and specific, can yield false negatives in cases of noncanonical breakpoints or novel genes[15,16].

Table 2 Comparison of neurotrophic tyrosine receptor kinase diagnostic tools[14,17].

	Sensitivity	Specificity	Detection of all fusions	Detection of fusion partner	Detection of protein expression	Turnaround time	Material required
IHC	Relatively high (NTRK1 and 2: 75%-96%, NTRK3: 50%-70%)	Relatively high	+	-	+	1 day	1 unstained slide
FISH	High	High	One per probe	One per probe	-	1-3 days	3 unstained slide
RNA NGS	High	High	+	+	+	2-4 weeks	15 unstained slide
DNA NGS	Moderate	High	+	+	-	2-4 weeks	10 unstained slide

NTRK: Neurotrophic tyrosine receptor kinase; NGS: Next-generation sequencing; IHC: Immunohistochemistry; FISH: Fluorescent in situ hybridization.

NGS, particularly RNA-based, offers high specificity and sensitivity. DNA-based NGS can assess multiple genomic alterations simultaneously, including mutations, amplifications, deletions, microsatellite instability status, and tumor mutation burden and fusions[16]. In contrast, RNA-based NGS offers a more accurate characterization of transcription evidence and specific gene involvement. However, the quality of RNA remains a limiting factor in RNA-based sequencing methodologies[17].

Despite the reliability of these methods, strong pan-TRK IHC expression without NTRK gene fusion is seen in less than 2% of uterine leiomyosarcomas[18]. Not all positive IHC or FISH findings indicate actual genes, highlighting the need for confirmatory gene analysis. Thus, accurate diagnosis, pivotal for targeted therapy, requires careful the interpretation of diagnostic tool.

In cases like that of our patient, where pan-TRK IHC shows positivity, but NGS reveals negative results for NTRK gene fusion, it is imperative to corroborate the findings with NGS, even in the presence of positive IHC results. The diagnostic algorithm presented in Figure 6 outlines and approach for assessing NTRK gene fusion in sarcoma. It suggests that a positive pan-Trk IHC result, while indicative, necessitates further testing through RNA-based NGS (preferred for its sensitivity), DNA-based NGS, or FISH to definitively determine the NTRK fusion status for treatment decisions[19].

Figure 6 Algorithm for diagnosing NTRK gene fusion in cervical sarcoma. NGS: Next-generation sequencing; IHC: Immunohistochemistry.

CONCLUSION

Sarcoma histotypes shows a relatively low incidence of NTRK rearrangement of less than 2%, necessitating a comprehensive, multi-step diagnostic process for accurate identification. Despite their rarity, the clinical significance of these tumors, particularly when located in the cervix, cannot be understated due to the potential effectiveness of TRK inhibitors in their treatment. Therefore, a two-tiered diagnostic approach will be beneficial for suspected NTRK gene fusion sarcomas. This approach should commence with pan-TRK IHC screening, followed by NGS in cases where protein expression is detected.