Masses in the forehead could represent a variety of lesions. Among these are mucoceles which are rare, benign but expansile lesions. We report the case of a 65-year-old female who presented with chief complaint of headache and a painless mass on her forehead after recent forehead trauma. Diagnostic work up demonstrated a frontal sinus mucocele and erosion through the posterior wall of the frontal sinus. Differential diagnosis, diagnostic considerations, and treatment options of forehead masses are discussed. A subcutaneous soft tissue mass on the forehead can be a frontal sinus mucocele. Therefore, clinicians are obligated to carefully evaluate and produce a differential diagnosis and undertake appropriate diagnostic testing prior to undertaking surgical intervention.
A mucocele is an epithelial lined cyst containing mucus, typically found in the frontal sinus. Malfunction of the drainage system is the primary source of mucocele formation.
In this paper, the authors present a mucocele that has an outward growth causing a large lump on the forehead, mimicking a lipoma like lesion.
The patient was a 65 year old female with a history of a fall and trauma to the forehead three months prior who presented with a chief complaint of a headache. She had no previous medical history. Post trauma she developed swelling over the midline of her forehead, which had progressive enlargement. She complained of temporal headaches four times a week lasting about an hour with no exacerbating or alleviating factors. Physical examination demonstrated a 4 x 4 cm round soft forehead mass in the midline. She was neurologically intact. She denied any double vision, dizziness, nausea, vomiting, neck stiffness, photophobia, or leakage of fluid from the nose.
Computed tomography (CT) scan of the paranasal sinuses was obtained without intravascular contrast. The examination consisted of 2 mm thick contiguous axial images with coronal and sagittal reformations.
Findings demonstrated a suspected frontal mucocele, which had penetrated the outer table into the anterior soft tissue (Fig 1A). The posterior table was also fractured pathologically (Fig 1B). The frontal sinuses were completely opacified and filled with soft tissue density material. The mass extended into the right ethmoid sinuses. The globes were normal.
The patient underwent a bifrontal craniotomy, resection of mucocele, and cranialization of the frontal sinuses. A bicoronal incision was made. In the midline of the frontal sinus region, a large bony defect with a protruding mass was noted and circumferentially dissected. The sac was punctured, and the fluid contents were aspirated. A bone flap was turned incorporating the frontal sinus. The soft tissue was then removed and sent for pathology. The inner cortical bone layer was then denuded and drilled down with a diamond bur.
A split thickness calvarial graft was harvested from the posterior portion of the bone flap and used to reconstruct the eroded calvarial defect from the mucocele and secured with titanium miniplates. Pericranium was then harvested more anteriorly and a vascularized pericranial graft was draped under the frontal pole and secured with sutures. The bone flap was then secured back to the skull using titanium plates (Fig 2).
Two large red-brown irregular lobulated soft tissue pieces measuring 4.0 x 2.5 x 1.0 cm and 1.5 x 1.0 x 0.5 cm were sent to the pathology department for evaluation.
The largest fragment appeared to be a cyst wall with a yellow capsule and contained necrotic debris.
Microscopic examination revealed a cystic lesion lined by pseudo-stratified ciliated respiratory epithelium (Fig 3A). The underlying sub-mucosa showed fibrous thickening. Within the cyst there was mucus, foamy macrophages, and needle shaped cholesterol clefts. Focal multi-nucleated giant cell reaction was also present (Fig 3B).
Masses in the forehead region can be divided into inflammatory, vascular, malignant, post traumatic, benign, or congenital category. Among them, dermoid cyst, a congenital lesion, is the most common lesion to develop in this area. As there can be an extension of the dermal cyst into the intracranial compartment, obtaining an imaging study is a prerequisite prior to its removal. Less common skull masses are mucoceles, meningiomas, multiple myeloma, plasmocytomas, hemangiomas, arteriovenous fistulae, lipoblastomas, neurofibroma, malignant tumors such as neuroblastoma, and benign neoplastic tumors such as fibrous dysplasia and ossifying fibroma. Obtaining a magnetic resonance (MRI) or CT scan allows for a proper evaluation and treatment planning for the removal of the masses in this region.
A history of forehead trauma should move up the mucocele on the differential diagnosis. Most common symptoms of the mucocele are headache, proptosis, diplopia, nasal congestion, and swelling over the forehead. However, the mucocele might go unnoticed for many years   . Mourouzis et al. described one patient who developed a mucocele 50 years after initial trauma .
Grossly, mucoceles are cysts filled with mucinous or gelatinous material. More than sixty percent of mucocele lesions occur in the frontal sinus, while 8-30% are in the ethmoid sinuses and around 5% are found in the maxillary sinuses .
Microscopically, a mucocele often shows nonspecific histological features. The clinical and radiological features of a mucocele can mimic neoplasm. The absence of tumor cells in the histopathological examination can aid in the diagnosis.
Mucous is secreted by the pseudo-stratified epithelium of the paranasal sinuses. Approximately one half of the mucous in the sinus re-circulates and the other half is dispelled . Ostium closure caused by inflammation, trauma, previous surgery, anatomical abnormality, osteoma or fibrosis can be the cause of mucous retention    . As a result of this retention, a mucocele is formed by the epithelium of the paranasal sinuses.
The development of a mucocele after trauma is mostly due to the compromised ventilation . Disruption of the posterior wall of the frontal sinus can make intracranial extension of the mucocele a life threatening condition. The intracranial portion can cause mass effect. Also, introduction of the mucocele contents could cause fulminant bacterial and/or chemical meningitis. In cases of prior cranialization of the frontal sinus, residual mucosa can continue to secrete mucus and cause mucocele formation.
Treatment options for frontal sinus mucoceles depend on the size of the mucocele, whether the anterior and posterior walls have been disrupted, and the degree of intracranial extension. If the mucocele is purely in the sinus without any anterior or posterior wall disruption, one option would be to observe with serial imaging. If there is growth of the mucocele over time, definitive surgical treatment should be considered. If there is only anterior wall disruption, several surgical options are available. One option is a minimally invasive endoscopic procedure to marsupialize the lesion with or without an external approach such as Lynch-Howarth frontoethmoidectomy . A more invasive procedure, such as a bicoronal approach, allows preservation of the esthetics along with sensory innervation to the forehead. With the latter approach, the mucocele along with the sinus mucosa are removed and the frontal recess is obliterated using gelfoam or a muscle graft. Fibrin glue can be used as a sealant. The sinus is then obliterated with either autogenous bone, fat, muscle or an allograft material such as hydroxyapatite. Kuhn suggests that if there is any doubt regarding complete removal of the sinus mucosa, the surgeon should not obliterate the sinus. Therefore, if there is a future recurrence, it would become easily visible on the imaging .
If there is disruption of the posterior wall of the frontal sinus with or without intracranial extension, definitive surgical treatment should be considered. This can include a bifrontal craniotomy, cranialization of frontal sinuses, evacuation and debridement of frontal lobe mucocele, obliteration of the frontonasal duct, and creation of a barrier between the sinonasal and intracranial compartments with a vascularized pericranial patch .
An important technical point is to take great care to remove all residual mucosa and epithelium to prevent recurrence. Due to inability of pseudostratified ciliated columnar epithelium to regenerate properly after being stripped off bone, it is of the utmost importance to use the bur to remove the residual mucosa. Using a diamond burr allows for both the mechanical and thermal destruction of epithelial cells invaginated in the vascular pits of Breschet to avoid recurrence   .
Giant frontal mucoceles are rare. Especially with a history of forehead trauma, mucoceles should be a prime consideration for the differential diagnosis. This case demonstrates that a subcutaneous mass may be a frontal mucocele in nature and it should be investigated appropriately. Careful evaluation including physical, ophthalmological and neurological examination and imaging with CT and/or MR should be considered. Diagnosis should be based on the history, physical examination and radiologic findings.
The authors have no financial support or commercial association that could potentially pose as a conflict of interest.
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