Characteristic imaging findings in a patient with chronic expanding hematoma on the floor of the mouth

Abstract

Chronic expanding hematoma (CEH) is defined as chronic hematoma enlargement for more than 1 month. Although CEH rarely occurs on the floor of the mouth, the need to distinguish these cases from malignant disease is critical, given the need for potentially extensive resection in patients with malignancy. We report a case of CEH on the floor of the mouth, which required differentiation from malignant tumor. A 42-year-old woman was referred to our hospital for a submucosal mass on the right floor of the mouth, with a diagnosis of class 3 on aspiration cytology. Computed tomography revealed a submucosal mass with peripheral calcification on the floor of the mouth, which exhibited a hypointense rim on T2-weighted imaging and gradual nodular-like enhancement in the periphery on contrast-enhanced magnetic resonance imaging. Enucleation was performed to reach a definitive diagnosis, and CEH was confirmed pathologically. Well-defined morphology, presence of calcification, a hypointense rim on T2-weighted imaging, and weak peripheral nodular-like enhancement may be characteristic findings of CEH on the floor of the mouth. Accordingly, these imaging features may aid in differentiating CEH from low-grade malignancies and in determining the optimal management strategy.

Introduction

Various submucosal masses, such as salivary gland tumors, schwannomas, and vascular malformations, may occur in the oral floor [1, 2]. Submucosal lesions of the floor of the mouth are clinically difficult to evaluate via physical examination, and computed tomography (CT) or magnetic resonance imaging (MRI) is often required for further evaluation. Differentiating benign from malignant tumors on imaging is crucial for determining the most appropriate treatment option, especially since patients diagnosed with malignant salivary gland tumors generally require surgical resection with a wide margin, depending on the extent of the disease [3]. However, preoperative diagnosis of a well defined submucosal mass on the floor of the mouth is often difficult owing to nonspecific imaging findings. We report a case of chronic expanding hematoma (CEH) on the floor of the mouth with relatively characteristic imaging findings that may aid in differentiating CEH from low-grade malignancy.

Case report

A 42-year-old woman consulted our hospital for an incidental mass identified by spinal MRI at the previous hospital. Intraoral examination revealed a mobile, well defined, 3 cm mass under the smooth mucosa of the floor of the mouth, which she had been aware of for a few years (Fig. 1). Laboratory test results revealed no abnormalities. Aspiration cytology performed at the previous hospital indicated a class 3 diagnosis, which was suggestive of malignancy, whereas biopsy revealed the presence of hyalinized connective tissues, vessels, and nerves. CT revealed a low-attenuation mass with coarse calcification in the periphery on the right side of the floor of the mouth (Fig. 2a), with no lymph node enlargement or distant metastasis. On MRI, the mass exhibited a hypointense rim on T2-weighted imaging (T2WI), whereas the central area exhibited heterogenous signal intensity (high and low) on T2WI and T1-weighted imaging (T1WI) (Fig. 2b, c, d). On dynamic MRI, gradual nodular-like enhancement was observed in the periphery of the mass (Fig. 2e, f, g), whereas no noticeable enhancement was observed in the central area. Based on the morphology, calcification, and weakness of contrast enhancement, the differential diagnosis included degenerative schwannoma, low-grade salivary gland tumor, and vascular malformation.

Fig. 1.

Intraoral findings. A mobile, well defined, 3 cm mass on the right side of the floor of the mouth (white arrow). The mucosa of the oral floor is smooth, suggesting a submucosal lesion

Fig. 2.

Computed tomography (CT) and magnetic resonance imaging (MRI) findings for the mass on the floor of the mouth. a Non-contrast-enhanced CT shows a well-defined mass with rim calcification on the floor of the mouth (black arrow). b On the coronal T2-weighted image, the mass appears to be within the genioglossus muscles (white arrow). c, d The central area of the mass is observed as an area of mixed low and high signal intensity on axial T1- and T2-weighted imaging (white arrowhead). e–g On axial dynamic contrast-enhanced and fat-suppressed T1WI, the periphery of the mass exhibited gradual and weak nodular-like enhancement 40, 90, and 120 s after injection of the contrast agent (black arrowhead)

To reach a definitive diagnosis, the tumor was surgically excised. Gross examination of the specimens revealed that the mass had a thick capsule with a hematoma and a yellowish-white solid component (Fig. 3a). Histologically, the capsule was composed of collagenous fibers, sporadic calcification, and enlarged vessels (Fig. 3b, c, d). The yellowish-white solid component was fibrotic and hyalinized, and the remaining part of the tumor was hemorrhagic. The collagenous capsule and hemorrhagic area corresponded to the low-signal-intensity rim and the areas of heterogenous signal intensity on T2WI, respectively. The areas exhibiting fibrosis and hyalinization were observed as areas of low signal intensity on T2WI and T1WI. Calcification was observed as high attenuation on CT and hypointensity on T2WI. Vessels around the margins of the mass in the pathological specimen exhibited nodular contrast enhancement on dynamic MRI. The mass was consistent with CEH based on its clinical course and pathological findings. The patient’s postoperative course was uneventful, and no recurrence was observed during 1 year of follow-up.

Fig. 3.

Pathological findings for the mass on the floor of the mouth. a Gross examination revealed a thick capsule comprised of a hematoma and fibrotic tissue. b Hematoxylin and eosin staining (× 40) revealed that the yellowish-white solid area includes a mixture of fibrosis and hyalinization (× 40). c Sporadic calcification at the margins of the mass (× 40). d Vessels are also seen within the margin of the mass (× 40)

Discussion

CEH, also known as organized/organizing hematoma, is defined as a chronically enlarging hematoma that develops over a period of more than 1 month [4, 5]. Researchers have postulated that decomposition of the hematoma leads to inflammation-induced increases in vascular permeability, resulting in bleeding from the fibrous capsule and hematoma growth [6]. Surgery, trauma, tuberculosis, or radiation therapy can cause CEH, and anticoagulants or antiplatelet agents can be a predisposing factor [7]. Nevertheless, the etiology of some cases of CEH remains uncertain. The usual treatment is complete resection, including the capsule, because the remaining capsule leads to recurrence [8]. There have also been reported cases of CEH treated with embolization and negative pressure wound therapy [7, 9]. Although CEH can occur anywhere in the body, most reported cases have occurred in the extremities and trunk [10, 11] and can occur in the sinonasal sinus and orbital cavity, but it is uncommon. However, CEH on the floor of the mouth has been described in only two previous case reports [12, 13], neither of which involved preoperative diagnosis of CEH given an unclear histological diagnosis [12, 13]. Similarly, in our case, we acquired only connective tissues using fine-needle aspiration and biopsy. Therefore, biopsy may not be helpful in cases of CEH of the oral floor, making preoperative diagnosis challenging.

Previous reports have described the general imaging findings of CEH as follows. (a) The peripheral rim of CEH, which corresponds to the capsule, exhibits low signal intensity on T2WI [14, 15]. (b) The inside of the CEH can exhibit a mosaic of various signal intensities from hyperintensity to hypointensity on T2WI [14, 15]. (c) The periphery of the CEH exhibits nodule-like enhancement. Although the internal portion of CEH rarely exhibits enhancement, a presence of enhancement in this area does not exclude the diagnosis of CEH [16], and (d) calcification of the peripheral rim may be observed [17]. All these findings were obtained in our case.

In one previous report, CEH in the oral floor was observed as a well-defined mass with poor contrast enhancement on CT and an area of relatively homogenous high signal intensity on T2WI [12]. The latter finding of internal homogeneity contrasts with findings in our case, which we suspect is related to the relatively short period of growth noted in the previous report (i.e., 2 months). In another case report, CEH of the floor of the mouth was observed as a well-defined mass with an egg-shaped area of calcification at the periphery, exhibiting heterogeneous high signal intensity on T1WI and homogeneous low signal intensity on T2WI [13]. Peripheral rim calcification and internal heterogeneity may reflect the long course of the disease (i.e., over 10 years), as in our case. According to previous reports, the imaging findings of CEH change over time as the hemoglobin degenerates and the bleeding repeats [15, 18, 19]. This pathology may account for the difference in the imaging findings of CEH in the two previous reports, and the internal heterogeneity is considered an imaging feature of long-standing CEH.

CEH must be distinguished from several other diseases that can affect the floor of the mouth, including salivary gland tumors, ranulas, epidermoid cysts, vascular malformations, and schwannoma [1]. Notably, imaging findings can be used to easily diagnose ranulas, epidermoid cysts, and vascular malformations. Although differentiating CEH from schwannoma can be challenging, differentiating CEH from malignant salivary gland tumors is critical, given the need for potentially extensive resection in patients with malignant salivary gland tumors. Fine-needle aspiration biopsy of a malignant salivary gland tumor is highly specific but not sensitive [20, 21]. Therefore, CT/MRI may aid in differentiating between them when the biopsy is negative. On imaging, high-grade malignant salivary gland tumors can be suspected based on invasive growth into the surrounding tissues. Low-grade types are well defined, making them difficult to distinguish from CEH. However, characteristic imaging findings such as peripheral rim calcification and a low-signal-intensity rim on T2WI suggest a diagnosis of CEH. We have summarized the differences between CEH and low-grade malignant salivary gland tumors in Table 1. In this case, FDG-PET/CT was not performed. According to some case reports on the imaging findings of FDG-PET/CT of CEH, the peripheral part of CEH shows various increased FDG uptake, making it challenging to distinguish CEH from malignant tumors [22, 23].

Table 1.

The differentiation between CEH and low-grade malignant salivary gland tumors

	CEH	Low-grade malignant salivary gland tumors
Symptom	Painless swelling	Painless swelling
Mass shape	Smooth, round	Smooth, round
CT	Calcification (occasional)	Calcification (rare)
MRI	Mixed low and high signal on T2WI, low signal rim on T2WI	High signal on T2WI
Pattern of enhancement	Nodular-like enhancement of periphery Gradual enhancement	Internal enhancement Gradual enhancement

CEH chronic expanding hematoma, CT computed tomography, MRI magnetic resonance imaging, T2WI T2-weighted imaging

In conclusion, characteristic MRI findings of a low-signal-intensity rim on T2WI, internal areas with mixed low and high signal intensity on T2WI, nodular-like enhancement of the periphery, and peripheral calcification may aid in differentiating CEH on the floor of the mouth from low-grade malignancy. Due to the limited reliability of FNA and biopsy in diagnosing CEH, these imaging findings provide critical additional information to support treatment decisions and may help avoid overtreatment.

Data availability

Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.