Introduction: Primary collision tumors composed of two histologically distinct components are rare in the head and neck, its pathobiological features remain unclear.
Case presentation: A man in his late 50s presented with paranesthesia pharynges and underwent upper endoscopy, followed by histopathological examination of biopsy specimens. He seems to have two tumors in the oropharynx with a size of 1.5*1.3cm, and an ulcer focus in the esophagus measuring about 1*0.8cm. Histopathological examination revealed a coexistence tumor of two components in the oropharynx, one was an adenocarcinoma with cribriform and solid growth pattern, with interstitial vitreous degeneration and central necrosis, the other was with a solid growth pattern, which was observed in both oropharynx and esophagus. The patient had a favorable outcome.
Conclusion: Correct diagnosis can be challenging and is essential and beneficial for the prognosis of the patient.
Squamous cell carcinoma is the most common epithelial malignancy of the head and neck. Approximately 1% of invasive carcinomas are adenoid cystic carcinoma. McGee et al introduced the currently accepted designation of ACC in 19651. ACC has a worse prognosis than the conventional SCC. However, because of the rarity of the coexistent tumor, there is no universal consent in the standard treatment of this devastating malignancy. To our knowledge, there have been few reports of the coexistence of the ACC with invasive SCC. In this case, there are collision tumor of SCC and ACC of the head and neck, with another invasive SCC in esophagus, which invaded to submucosa.
A man in his late 50s presented with paranesthesia pharynges for 25 days, no obvious dysphagia and any significant health problems. Magnetic resonance imaging (MRI) showed thickening sinus mucosa in the right side of piriform recess, iso-intensity on T1-weighted image, and mild hyper-intensity on T2-weighted image and DW image, with inhomogeneous enhancement. Standard upper endoscopy showed a protruded lesion at 35 cm from the Incisor. Hypopharyngectomy and partial esophagectomy were subsequently performed. The surgical specimen showed a solid tumor in the right dipper, which was involved in the piriform recess with a size of 1.5*1.3cm, and another ulcer focus in the esophagus measuring about 1*0.8cm.
The hematoxylin and eosin (H&E)-stained section showed the tumor was composed of two distinct morphological types. One was a SCC component which had a solid pattern with a small area of squamous cell carcinoma invasion (Fig. 1A、B) and vascular tumor thrombus; the other was an adenocarcinoma with a cribriform and solid growth pattern, interstitial vitreous degeneration and central necrosis were also observed (Fig. 1C), tumor cells showed moderate-to-severe atypia and no clear nerve invasion, mitotic activity were easily seen; There was an abrupt transition between these two components (Fig. 1D).
To further classify the tumor, a panel of immunohistochemical stains was performed. Immunohistochemical analysis revealed that CK7 was positive for the ACC but negative for the SCC component (Fig. 2A), CK5/6 and p63 were diffusely and strongly positive in SCC but patchily positive in ACC (Fig. 2B), p63 was only expressed in the outer luminal surface of the pseudocysts of the ACC component (Fig. 2C), furthermore, CD117 positively showed in the inner luminal surface of the pseudocysts of the ACC component but negative in the SCC component (Fig. 2D), p53 were negative in both of the two components (Fig. 2E); MYB, MYBL1 and NFIB genes detected by in situ hybridization method harbored no gene fusion in ACC components (Fig. 2F).
About 92% of ACC showed positive expression of CD117, which is the valuable factor in diagnosing ACC. CD117 was mainly expressed in the inner luminal surface of the pseudocysts of ACC, however, full-thickness expression could be observed in solid nest of cancer1. In this case, CD117 mainly expressed in the cytoplasm and cell membrane of cancer cell, which is consistent with earlier reports.
Fusion gene of MYB-NF1B leaded by t(6;9) (q22-23;p23-24) translocation is significant discovery for the diagnosis of ACC2–4, but only happened in about 50% of ACC5. According to recent reports, other molecular events such as NOTCH, PI3K signaling pathways, and epigenetic modification and DNA damage repair were also found to play an important role in the tumorigenesis of ACC6, 7. There is no gene fusion observed in this case, implied other mechanisms in the progression of ACC, which conforms to the reports.
ACC has tubular, cribriform, solid growth pattern. Any solid growth pattern is the unfavorable factor of DSS and RFS. AJCC also suggested that clinic stage and more mitosis were also independent prognostic factors of ACC8. The solid growth pattern and mitosis were easily observed in this case, suggested the poor prognosis of the patient.
The differential diagnosis included basaloid squamous cell carcinoma, basaloid squamous cell carcinoma with adenoid cystic-like features, basal cell carcinoma. Basaloid squamous cell carcinoma with adenoid cystic‐like features could be excluded with an abrupt transition between these two components. Basal cell carcinoma could be ruled out by interstitial vitreous degeneration and cribriform growth pattern, CK5/6 negative expression, p63 was only positive in the outer luminal surface of the pseudocysts and CD117 expression pattern could further excluded the basal cell carcinoma and basaloid squamous cell carcinoma.
ACC is much more aggressive than SCC. However, because of the rarity of the coexistent tumor, there is no universal consent in the standard treatment of this devastating malignancy. Generally, treatment for ACC is the same as that for SCC of the head and neck; a combination of surgery and radiation therapy has been the primary treatment. Therefore, early recognition of the coexistence of ACC and SCC is significant to guide clinical management and is extremely beneficial for patients, a close follow up is highly recommended.
The authors would like to thank Ms Mei Kong and Zhihui Wang for their technical assistance.
This project was supported by the fund of National Natural Science Foundation of China (No. 82002488) and Natural Science Foundation of Zhejiang Province (No. LQ21H160020).
Each author made substantial contributions to the conception and design of this paper. The author(s) read and approved the final manuscript.
Availability of data and materials
All the data regarding the findings are available within the manuscript.
Ethics approval and consent to participate
This case report was approved by the clinical research ethics committee of the First Affiliated Hospital of Zhejiang University, College of medicine, reference number 浙大一院伦审2022研第154号-快.
The authors state that there are no conflicts of interest to disclose.