Benign tumors of sinuses

Benign neoplasms of nasal sinuses:

Osteomas:

These tumors are commonly seen in frontal sinus followed by ethmoid and maxillary sinuses. These lesions are commonly asymptomatic and are incidental findings on routine imaging. Surgery is performed if these lesions extend beyond the boundaries of the sinus cavity, cause obstruction to drainage of sinues, cause obstruction to the nasolacrimal duct etc.

Resection of small / medium sized osteomas can be safely performed using endoscopy. Giant frontal sinus osteomas can be approached by a combined external and endoscopic procedure. Sinus cavity obliteration is not needed if the mucous membrane is intact.

Even though osteomas are asymptomatic, they can cause the following symptoms:

Head ache

Epistaxis

If surgery is contemplated, CT imaging of paranasal sinuses (three dimensional studies) should be performed in order to determine the exact size and orientation of the tumor. MR imaging plays a vital role in differentiating tumors from that of inflammatory disorders.

Fibrous dysplasia:

This can affect any of the paranasal sinuses. Symptoms correspond to the sinus involved.

Maxillary sinus fibrous dysplasia:

Fibrous dysplasia is a developmental disorder of maxilla in which immature woven bone is formed directly from abnormal fibrous tissue. It is characterised by an expansile lesion of fibro osseous tissue. Fibrous dysplasia is of two types:

1. Mono ostotic fibrous dysplasia 2. Poly ostotic fibrous dysplasia

Mono ostotic fibrous dysplasia affects a single bone commonly affecting a rib or facial bones. It is also more common than poly ostotic fibrous dysplasia. This condition may be associated with systemic conditions like precocious puberty, and skin pigmentation. This condition if associated goes under the name McCune - Albright Syndrome. This lesion is active while the bone is growing. The lesion becomes inactive when the growth stops. The activity of the disease may increase later during pregnancy.

Poly ostotic variety affects many bones nearly 75 % of skeletal tissue may be affected. This lesion may remain active throughout life.

Pathology: Disorganised immature bone surrounded by immature fibrous tissue is seen in the dysplastic areas. This tissue doesnot have the capacity to mature into a lamellar bone. Hence the normal mechanical integrity of the bone is lost affecting the weight bearing bones in polyostotic fibrous dysplasia. Pain may be disabling. Fractures are common. Fractured bones heal with more immature bone tissue thereby accentuating the condition.

    Rarely fibrous dysplasia may become more aggressive and dedifferentiate causing (desmoplastic fibroma).  Sometimes the tissue may undergo sarcomatous transformation. 

Risk factors for malignant transformation include: 1. Polyostotic form 2. Post radiation sequelae 3. Facial bone involvement 4. Albright's syndrome

Usually fibrous dysplasia affects affects people in their childhood / teens. Males are commonly affected than females. Albright syndrome is an exception wherein female preponderance is more.

Involved bones consists of immature and relatively undifferentiated fibrous connective tissue that fails to produce normal amounts of collagen. The collagen produced are not oriented appropriately to withstand the pressure stress.

Fibrous dysplasia of maxilla:

Fibrous dysplasia of the facial skeleton commonly involves the maxilla. It commonly involves one maxilla. The patient manifests with unilateral swelling of cheek (firm in consistency). Patient may have unilateral proptosis because dysplasia involves the boundaries of the orbit reducing the space available for the orbital contents. Some of these patients may suffer loss of vision due to entrapment of optic nerve in the dysplastic process.

Lab investigations:

1. Serum alkaline phosphatase levels are often elevated depending on the extent of bony disease.

2. Serum calcium phosphate may also be elevated

3. Pituitary gonadotropins and gonadosteroids are assessed to assist in the workup of precocious puberty.

Xray shows an expansile bony lesion. Bone walls are intact. Maxillary sinus is obliterated.

CT scan shows a lesion that is confined to the interior of the bone with no soft tissue component. It is helpful in distinguishing fibrous dysplasia from a malignancy. Features of malignancy include osteolysis, destruction of sclerotic margins, and cortical destruction with soft tissue extension. The bony lesion shows a homogenous matrix with obliteration of maxillary sinus cavity.

Technetium Tc 99m methylene diphosphonate (MDP) bone scan can be done to distinguish mono ostotic from poly ostotic lesions. Increased uptake is more common in poly ostotic lesions.

Treatment:

Medical: Underlying endocrine deficiency if any must first be treated. Vitamin D and bisphosphonates (after physeal closure) may be helpful in ameliorating pain and possibly in reconstituting lesions with normal bone.

Surgical: Curettage of the affected bone with filling up of the defect using a bone graft is the advised surgical procedure. In the case of maxilla the affected bone bleeds extensively when an attempt is made to curette it. Adequate amount of blood must be reserved before surgery. The surgical procedure is known as Parring of the maxilla.

Fibrous dysplasia of ethmoid sinus:

The onset of this disorder occurs usually in the childhood age, and the frequency gradually increases during puberty and adolescence. Gene mutation involving GNAS1 has been postulated as the probable etiological cause.

CT scan is diagnostic. This happens to be the first choice investigation in fibrous dysplasia. The mass characteristically appears as a ground glass.

If fibrous dysplasia involves posterior ethmoid then it could lead to blindness due to involvement of optic nerve at the level of orbital apex.

Fibrous dysplasia involving the sphenoid sinus is rather rare.

Fibro osseus lesions:

These are benign lesions characterized by replacement of normal bone by fibrous cellular stroma containing varying amounts of foci of mineralization / ossification. These lesions very rarely affect the paranasal sinuses. These lesions can be divided into 3 different entities i.e.

Fibrous dysplasia - already described

Osteoma - already described

Ossifying fibroma - These lesions are incidental findings during imaging. It can also be symptomatic in relation to a mass effect of the tumor on adjacent structures. When the lesion protrudes out of the nasal cavity then it can be visualized easily. In these lesions there is a sharp delimitation from the surrounding healthy tissue, which is in contrast to fibrous dysplasia.

Surgical removal of ossifying fibroma is rather difficult when compared to that of osteoma. Total resection is mandatory as there is a higher percentage chance of recurrence.

Ameloblastomas:

These are locally aggressive tumors with a high propensity for recurrence. These tumors are believed to arise from remnants of dental lamina or odontogenic epithelium. Tumors arising from maxillary sinus could secondarily extend through nasal and paranasal sinus cavities.

Two predominant growth patterns have been noticed:

Follicular

Plexiform

These are slow growing and locally aggressive tumors. These tumors commonly arise from the jaws and are frequently associated with unerupted tooth. It commonly appears in the thrid - fifth decades in life. This tumor has no gender predilection.

These tumors can be managed by performing radical surgical excision.