Neoplasms of the Sinonasal Tract

Anatomic Site

• For staging purposes the sites of inclusion include:

  • Maxillary sinus

  • The nasoethmoid complex, which includes:

    • –

      Nasal cavity

    • –

      Ethmoid sinuses

Nasal Cavity

• The nasal cavity is subdivided into four subsites:

  • Septum

  • Floor

  • Lateral wall

  • Vestibule

Maxillary Sinus ( Fig. 3-1 )

• The maxillary sinus is divided into right and left.

• Ohngren line connecting the medial canthus of the eye to the angle of the mandible dividing the maxillary sinus into an anteroinferior portion (infrastructure) and superoposterior portion (suprastructure) structures (see Fig. 3-1 ):

  • Carcinomas of the infrastructure are associated with a good prognosis.

  • Carcinomas of the suprastructure are associated with a poor prognosis:

    • –

      The poorer prognosis with carcinomas of the suprastructure reflects early access of these tumors to critical structures, including the eye, skull base, pterygoids, and infratemporal fossa.

Clinical

• Ectodermally derived lining of the sinonasal tract, termed the Schneiderian membrane, may give rise to three morphologically distinct benign papillomas collectively referred to as Schneiderian or sinonasal-type papillomas. The three morphologic types are:

  • Inverted

  • Oncocytic (cylindric or columnar cell)

  • Exophytic (fungiform, septal) papillomas

• Collectively, Schneiderian papillomas represent less than 5% of all sinonasal tract tumors.

• As reported in the literature, among sinonasal-type papillomas, the exophytic (septal) papilloma is the most common type; however, practical experience indicates that the inverted type is the most common subtype; the oncocytic type is the least common.

• In general, the sinonasal-type papillomas occur over a wide age range but are rare in children:

  • Inverted papillomas are most common in the fifth to eighth decades.

  • Oncocytic papillomas occur in a somewhat older age range (greater than 50 years) and are uncommon in patients younger than the fourth decade of life.

  • Exophytic (septal) papillomas tend to occur in a younger age group.

• Localization:

  • Exophytic papillomas almost invariably are limited to the nasal septum.

  • Inverted papillomas occur along the lateral nasal wall (middle turbinate or ethmoid recesses) with secondary extension into the paranasal sinuses (maxillary and ethmoid, and less often sphenoid and frontal); less frequently, inverted papillomas may originate in a paranasal sinus.

  • Oncocytic papillomas also are most often seen along the lateral nasal wall but may originate within a paranasal sinus (maxillary or ethmoid).

  • Inverted and oncocytic subtypes rarely occur on the nasal septum.

  • Inverted papillomas may occur in a paranasal sinus without involvement of the nasal cavity.

  • Schneiderian papillomas have a tendency to spread along the mucosa into adjacent areas.

  • Although uncommon, the sinonasal-type (Schneiderian) papillomas may originate in the nonsinonasal tract sites, including the nasopharynx or the ear:

    • –

      Typically in such situations there is no connection to the sinonasal tract and/or to a Schneiderian papilloma extending from the sinonasal tract to these locations.

    • –

      In all likelihood such Schneiderian-type papillomas occurring in nonsinonasal tract sites arise from misplaced ectodermal-derived epithelial rests from the sinonasal tract.

• Typically, Schneiderian papillomas are unilateral; bilateral papillomas, in particular the inverted subtype, may occur with reported incidence of up to 10%:

  • In the presence of bilaterality, clinical evaluation to exclude the possibility of extension from unilateral disease (i.e., septal perforation) should be undertaken.

• Symptoms vary according to site of occurrence and include airway obstruction, epistaxis, asymptomatic mass, and pain.

• Schneiderian papillomas may occur simultaneously with nasal inflammatory polyps or other lesion types including (but not limited to) sinonasal hamartomas.

• Radiology: appearance varies with extent of disease:

  • A soft tissue density is seen early in the disease.

  • Opacification and mucosal thickening are present with more extensive disease.

  • Evidence of pressure erosion of bone may be seen.

• Human papillomavirus (HPV) types 6/11, less often 16, and rarely other HPV types (e.g., HPV57), have been found in septal and inverted papillomas by various molecular biologic analyses (in situ hybridization and/or polymerase chain reaction):

  • Strong association identified between HPV and exophytic papillomas

  • Association between HPV and inverted papillomas less well defined:

    • –

      Approximately 38% of inverted papillomas reported to be positive for HPV by molecular biologic evaluation

  • To date, molecular biologic analysis of onco­cytic papillomas has not identified the presence of HPV.

  • Whether there is a cause and effect between the presence of HPV and the development of Schneiderian papillomas remains to be determined.

  • p16(INK4a) not considered a useful surrogate marker for HPV detection across the various types of Schneiderian papillomas.

  • HPV detection rates increase in inverted papillomas with epithelial dysplasia and malignant transformation (i.e., carcinoma) of inverted papillomas:

    • –

      Increasing ratio of high-risk to low-risk HR HPV types as compared with “conventional” inverted papillomas (i.e., without dysplastic epithelium)

• Epstein-Barr virus has not been found to be associated with Schneiderian papillomas.

Pathology

Treatment and Prognosis (for All Papilloma Types)

• Treatment for all sinonasal-type papillomas is complete surgical excision, including adjacent uninvolved mucosa; the latter is necessary because growth and extension along the mucosa results from the induction of squamous metaplasia in the adjacent sinonasal mucosa:

  • Adequate surgery includes a lateral rhinotomy or medial maxillectomy with en bloc excision.

• Schneiderian papillomas of all histologic types will recur if incompletely resected; recurrence probably represents persistence of disease instead of multicentricity of the neoplasm.

• In general, prognosis is good following complete surgical excision; however, if left unchecked, these neoplasms have the capability of continued growth with extension along the mucosal surface with destruction of bone and invasion of vital structures (e.g., central nervous system, others).

• Adjuvant therapy (chemo- and radiotherapy) has not been demonstrated to be beneficial in sinonasal papilloma:

  • Radiation may prove beneficial in a select population of patients with unresectable tumors due to locally advanced disease.

• Complications associated with Schneiderian papillomas include recurrence and malignant transformation:

  • Inverted papillomas and oncocytic papillomas can undergo malignant transformation.

  • Incidence of malignant transformation varies per subtype:

    • –

      Malignant transformation reported for the inverted subtype ranges from 2% to 27% but is more likely around 11%.

    • –

      Malignant transformation reported for the oncocytic subtype ranges from 4% to 17%.

    • –

      Malignant transformation relative to exophytic (septal) papilloma rarely, if ever, occurs.

  • Majority of the malignancies occurring in association with Schneiderian papillomas are squamous cell carcinomas (keratinizing and nonkeratinizing), varying in appearance from well to poorly differentiated; less frequently, other carcinomas may occur, including verrucous carcinoma, mucoepidermoid carcinoma, spindle cell squamous carcinoma, small cell carcinoma, adenocarcinoma, and sinonasal undifferentiated carcinoma.

  • Carcinoma may occur synchronously or metachronously with the papilloma:

    • –

      Metachronous carcinomas develop with a mean interval of 63 months (range 6 months to 13 years) from the onset of the papilloma to the development of the carcinoma.

  • Carcinomatous foci may be limited or extensive and may show epithelial dysplasia as well as carcinoma in situ or invasive carcinoma.

  • Evidence of a pre-existing papilloma may be present with obvious transition from benign papilloma to overt carcinoma; other possibilities include a tumor that is predominantly benign (papilloma) with only limited foci of malignancy or a tumor that is predominantly a carcinoma with very limited residual papilloma.

  • In some cases, there may be no residual evidence of a pre-existing benign tumor and only by history was the patient known to have had a previous benign sinonasal papilloma.

  • There are no reliable histologic features that predict which papillomas are likely to become malignant:

    • –

      Papillomas with increased cellularity, pleomorphism, and increased mitotic activity do not necessarily become malignant.

    • –

      Presence of moderate to severe intraepithelial dysplasia is a potential indicator of malignant transformation.

      • ▪

        Dysplastic epithelium will have increased p16, p53, and Ki67 expression.

    • –

      Surface keratinization and dyskeratosis have anecdotally been considered as possible predictors of malignant transformation.

    • –

      Any sinonasal papilloma that shows moderate to severe intraepithelial dysplasia or has surface keratinization should prompt thorough histologic examination of all resected tissue to exclude the presence of malignancy.

  • There is no correlation between the number of recurrences and the development of carcinoma.

• Treatment for malignant transformation of a sinonasal papilloma includes surgery and radiotherapy.

• Prognosis for patients with malignant transformation varies:

  • In some patients the carcinomas are only locally invasive with favorable prognosis following treatment.

  • In other patients there may be extensive invasion with involvement of vital structures and/or metastatic disease; these patients generally have a poor clinical outcome irrespective of therapeutic intervention.

Clinical

• Squamous papillomas represent the most common benign neoplasms of the upper aerodigestive tract mucosa and are commonly seen in the oral cavity and larynx; less often, squamous papillomas occur in the nasopharynx and nasal vestibule.

• For a more complete discussion on squamous papillomas see Section 2, Oral Cavity, and Section 5, Larynx.

• Nasal vestibular squamous papillomas are of cutaneous origin.

• In contrast to the sinonasal-type papillomas, squamous papillomas of the nasopharynx are endodermally derived.

• Squamous papillomas are exophytic, warty, or cauliflower-like tumors ranging in size from a few millimeters up to 3.0 cm in greatest dimension.

• Histologically, these tumors are composed of benign squamous epithelium arranged in multiple finger-like projections with prominent fibrovascular cores.

• In contrast to the sinonasal-type papillomas, cuta­neous squamous papillomas lack intraepithelial mucocytes.

• In squamous papillomas the squamous epithelium is free of dysplastic change.

• In general, these tumors lack surface keratin, but in any tumor there may be (hyper)keratosis, as well as para- and orthokeratosis:

  • Presence of surface keratin carries no additional risk for the development of carcinoma.

• Surgical excision is the treatment of choice and is curative.

• Recurrences occur infrequently and relate to inadequate excision.

• Malignant transformation does not occur.

Clinical

• No gender predilection; wide age range commonly seen in the fourth and fifth decades of life but uncommon under 16 years of age

• Most often identified in the anterior portion of the nasal septum referred to as Little's area or Kisselbach's triangle; next most common sinonasal location is the tip of the turbinates.

• Hemangiomas of the sinonasal tract tend to be mucosally based but also may arise from within the osseous components of this region (intraosseous hemangiomas).

• Aside from the lobular capillary hemangioma, other types of hemangiomas of the sinonasal cavity and nasopharynx are rare.

• Most common clinical complaint is epistaxis; an obstructive painless mass may be present.

• Pathogenesis remains unclear:

  • A minority of cases may be associated with prior trauma.

  • LCH may occur in association with pregnancy and in association with oral contraceptive use, suggesting that hormonal factors may be involved.

  • A hormonal role is further supported by the regression of these tumors following parturition; however, immunohistochemical evaluation failed to identify estrogen or progesterone receptors in any of these tumors.

  • The mechanism for the regression of pregnancy-related pyogenic granuloma after parturition remains unclear; proposed mechanisms for regression include the absence of vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2), causing blood vessels to regress:

    • –

      Amount of VEGF has been found to be high in the LCH in pregnancy and almost undetectable after parturition, suggesting that a lack of VEGF is associated with apoptosis of endothelial cells and regression of these tumors.

    • –

      No role for Ang-2 alone in regression has been found.

Pathology

Differential Diagnosis

• Sinonasal-type hemangiopericytoma-like tumor:

  • Diffuse growth pattern composed of a single cell type and presence of perivascular hyalinization contrast to the findings seen in LCH

• Angiofibroma

• Infantile hemangiomas:

  • GLUT1 positive

  • See Section 6, Salivary Gland for more detailed discussion.

• Angiosarcoma

Treatment and Prognosis

• Treatment includes conservative but complete surgical excision of the lesion.

• Prognosis following excision is excellent.

• Recurrences are relatively infrequent.

Clinical

• Represents less than 1% of all sinonasal tract tumors

• No gender predilection; occurs over a wide age range but is most commonly seen in the sixth to seventh decades of life

• Typically presents as a unilateral nasal mass with obstruction and epistaxis; extension into adjacent paranasal sinuses may occur, but isolated involvement to a paranasal sinus is uncommon.

• Radiology:

  • Opacification of the involved sinus

  • Bone erosion due to pressure may be seen.

  • Arteriographic findings reveal a richly vascular neoplasm.

• There are no known etiologic factors.

• May rarely cause oncogenic osteomalacia (OO):

  • OO is a rare paraneoplastic syndrome of osteomalacia due to phosphate wasting.

  • Phosphaturic mesenchymal tumor (mixed connective tissue variant) extremely rare, distinctive tumor frequently associated with OO

  • Overexpression of fibroblast growth factor-23 (FGF-23), a phosphaturic hormone, shown in phosphaturic mesenchymal tumor

  • Phosphaturic mesenchymal tumor is a soft tissue tumor histologically characterized by:

    • –

      Hemangiopericytoma-like areas and osteoclast-like giant cells with or without osseous and cartilaginous metaplasia

    • –

      ”Grungy” calcified matrix identified

Pathology

Differential Diagnosis

• Lobular capillary hemangioma

• Nasopharyngeal angiofibroma

• Glomus tumor (glomangioma)

• Solitary fibrous tumor (SFT):

  • In contrast to the solitary fibrous tumor, sinonasal hemangiopericytoma-like tumor lacks the presence of “ropey” keloidal-appearing collagen or amianthoid fibers and bcl-2 staining.

  • Sinonasal hemangiopericytoma-like tumor and SFT may show the presence of CD34 immunoreactivity; however, the extent of CD34 immunoreactivity varies:

    • –

      In sinonasal hemangiopericytoma-like tumor CD34 staining if present is localized and not diffuse.

    • –

      In solitary fibrous tumors CD34 tends to be diffuse and strong.

  • STAT6 immunoreactivity seen in SFT but not in sinonasal hemangiopericytoma-like tumor

  • NAB2-STAT6 gene fusion seen in SFT but not in sinonasal hemangiopericytoma-like tumor

• Smooth muscle tumors (leiomyoma and leiomyo­sarcoma)

• Benign and malignant fibrohistiocytic neoplasms

• Synovial sarcoma

• Mesenchymal chondrosarcoma

Treatment and Prognosis

• Surgery is the preferred treatment and should include complete excision to include tumor-free margins.

• Considered radioresistant neoplasms

• Indolent behavior with overall 5-year survival rates of greater than 90%

• Local recurrence may occur in as high of 30% of cases and is likely due to inadequate surgical excision:

  • Recurrence can be anticipated over extended follow-up periods (1 to 2 decades).

• Aggressively behaving sinonasal hemangio­pericytoma-like tumors are uncommon and include tumors that are locally destructive or are metastatic.

• Findings potentially linked to aggressive behavior include:

  • Large tumor size (greater than 5 cm)

  • Marked nuclear pleomorphism

  • Increased mitotic activity

  • Necrosis

  • Invasive growth (e.g., bone)

  • Proliferation index of greater than 10%

• Metastatic tumor is uncommon; if it occurs, spread usually is to regional lymph nodes and lung and is preceded by (one or more) recurrent tumor.

Clinical Features

• No gender predilection; occurs in adults

• Clinical presentation may include airway obstruction, chronic sinusitis, visual field defects, cere­brospinal fluid leakage, and endocrinopathic manifestations (e.g., Cushing's syndrome, hirsutism).

• Most common ectopic sites of occurrence are the sphenoid sinus followed by the nasopharynx:

  • Other less common sites include the nasal cavity and ethmoid sinus; rarely, may involve the clivus.

Pathology

Differential Diagnosis ( Table 3-3 )

• Paraganglioma

  • Rarely if ever occurs in the sinonasal tract

• Olfactory neuroblastoma (ONB)

  • ONBs predominantly arise in the superior aspect of the nasal cavity and rarely originate from the sphenoid sinus, the most common location for EPA.

  • Presence of diffuse and intense cytokeratin staining as seen in EPA essentially excludes a diagnosis of ONB, which is typically cytokeratin negative or at most only focally positive.

• Neureondocrine carcinoma (e.g., carcinoid tumor):

  • Carcinoid tumor (well-differentiated neuroendocrine carcinoma) is so uncommon in the sinonasal tract as to be considered nonexistent.

• Malignant epithelial neoplasms (e.g., SNUC, other)

Treatment and Prognosis

• Wide surgical resection is the preferred treatment:

  • Complete removal may prove curative without recurrent or progressive tumor, and with resolution of endocrinopathic effects associated with the tumor.

  • Recurrence not uncommon especially for large tumors and/or incompletely excised tumors

• Medical therapy, bromocriptine (dopamine agonist) may be employed to control endocrinopathic effects of the tumor.

• Although benign, EPAs may be large and infiltrative, including into bone precluding surgical extirpation; in such cases radiation therapy can be used.

• Rarely, malignant transformation may occur.

Clinical

• SFTs are rare but do occur in the upper aerodigestive tract, primarily involving the nasal cavity and paranasal sinuses.

• Patients with tumors in these sites present with nasal obstruction:

  • Usually, the symptoms have been present for an extended period of time (a year or more).

Pathology

• These tumors typically are polypoid.

Differential Diagnosis

• Sinonasal hemangiopericytoma-like tumor

• Smooth muscle tumors (leiomyoma)

• Peripheral nerve sheath tumors

• Fibrohistiocytic tumors

• Fibromatosis

• Nasopharyngeal angiofibroma

Treatment and Prognosis

• Given their tendency to be polypoid, solitary fibrous tumors of the sinonasal tract are amenable to complete surgical resection.

• Complete surgical resection is usually curative:

  • Recurrences generally a function of incomplete excision

• SFTs of the nasopharynx may be more difficult to completely excise; despite incomplete resection, these tumors are not generally associated with adverse biologic behavior at this anatomic location.

• Malignant transformation of SFT may occur in particular for intrathoracic or soft tissue but rarely for those of head and neck sites; histologic features associated with malignancy include:

  • Increased cellularity, pleomorphism, and increased mitotic activity (>4/10 high-power fields)

Clinical

• Relatively uncommon neoplasm in the head and neck accounting for less than 5% of all fibrous histiocytomas

• More common in men than in women; occurs over a wide age range with a median age in the fifth decade of life

• Excluding cutaneous sites, the most common location in the head and neck is the nasal cavity and paranasal sinuses; other more common sites of occurrence include neck, larynx, and trachea.

• Symptoms vary according to site and include painless mass, nasal obstruction, epistaxis, pain, facial asymmetry, proptosis, loosening of teeth, hemoptysis, dyspnea, and stridor.

Pathology

Differential Diagnosis

• Nodular fasciitis

• Fibromatosis (see Section 4, Neck, for more complete discussion)

• Benign peripheral nerve sheath tumors (benign schwannoma, neurofibroma)

• Leiomyoma

• Solitary fibrous tumor

• Dermatofibrosarcoma protuberans (DFSP):

  • See Section 7, Ear and Temporal Bone, for a more complete discussion.

  • Most frequent on the trunk and extremities

  • Histologically, DFSP infiltrates the dermis and subcutis and in its central aspect is composed of plump fibroblasts arranged in a distinct storiform pattern; cellular pleomorphism is mild and variable mitotic activity is seen.

  • CD34 immunoreactive

  • Wide local excision is the preferred treatment.

• Undifferentiated pleomorphic sarcoma (formerly malignant fibrous histiocytoma)

Treatment and Prognosis

• Complete surgical excision is generally curative.

Clinical

• In general, one of the least common mesenchymal tumors in the head and neck area owing to the relative absence of smooth muscle in this region:

  • Smooth muscle found in association with blood vessels or cutaneous appendages represents origin for many head and neck leiomyomas

  • Leiomyoma arising from blood vessels termed vascular leiomyoma

• More common in men than in women; may occur in all ages but generally is a tumor of adult life with a peak incidence in the sixth decade of life

• Most common sites of occurrence in the head and neck are:

  • Skin and oral cavity (lips, tongue, and palate)

  • Other sites that may be affected include the sinonasal tract and larynx.

• Within the sinonasal tract leiomyomas most often involve the turbinates.

• Usually presents as a painless mass and nasal ob­­struction; other symptoms include dysphagia, voice changes, and pain.

Pathology

Differential Diagnosis

• Peripheral nerve sheath tumor (neurofibroma, schwannoma)

• Solitary fibrous tumor

Treatment and Prognosis

• Complete surgical excision is curative.

• Rarely recurs

Clinical

• Sinonasal osteomas are more common in men and occur over a wide age range but are most often encountered in the second to fourth decades of life.

• These tumors are usually asymptomatic and are found only by radiographic studies.

• Symptoms associated with paranasal sinus osteomas include headaches, facial swelling or deformity, and ocular disturbances; meningitis secondary to cranial cavity extension and sinus or aural obstruction may occur.

• Most common sites of involvement are the paranasal sinuses with the frontal and ethmoid sinuses most often involved (frontal > ethmoid > maxillary > sphenoid); other sites of involvement include:

  • Temporal bone (osseous external auditory canal), skull, mandible, maxilla

• Radiology:

  • Sharply delineated radiopaque lesion confined to bone or protruding into a sinus

• Cause linked to trauma, infection (sinusitis), and development

• Sinonasal osteomas usually occur as a single lesion but may be associated with Gardner syndrome:

  • Autosomal dominant inheritance

  • Sentinel lesion for adenomatous polyposis coli (APC)

  • Characterized by intestinal (colorectal) polyposis, soft tissue lesions (fibromatosis, cutaneous epidermoid cysts, lipomas, leiomyomas), and multiple craniofacial osteomas

Pathology

Differential Diagnosis

• Exostosis

Treatment and Prognosis

• Unless symptomatic, osteomas require no treatment.

• Symptomatic osteomas require complete surgical excision, which is curative.

• No known link to the development of osteo­sarcoma

Clinical

• No gender predilection; generally occurs in younger age groups (first and second decades) but can occur over a wide age range, including older individuals.

• Presenting symptoms include facial swelling, nasal obstruction, pain, sinusitis, headache, and proptosis.

• These lesions may occur in any area of the sinonasal tract but are most frequent in the ethmoid sinus and supraorbital frontal region (ethmoid > nasal cavity > maxillary sinus > frontal sinus); the orbit may also be involved.

• There may be involvement of a single site or multiple sinuses.

• Radiology:

  • Lytic or mixed lytic/radiopaque osseous and/or soft tissue mass varying from well-demarcated to invasive with bone erosion

• Presenting symptoms include facial swelling, nasal obstruction, pain, sinusitis, headache, and proptosis.

Pathology

Differential Diagnosis

• Fibrous dysplasia (see Table 3-4 )

• Ossifying fibroma (see Table 3-4 )

• Osteoblastoma

• Osteosarcoma

• Psammomatoid meningioma

Treatment and Prognosis

• Complete surgical excision is the preferred treatment.

• Prognosis is good following complete excision but, if margins are involved, recurrences often occur, and the tumors may behave in an aggressive manner with local destruction and potential invasion into vital structures.

Clinical

• Chondromas of the sinonasal tract and nasopharynx are rare.

• The most frequent sites of occurrence include the nasal septum and the nasopharynx.

• Radiology:

  • Sinus opacification or a circumscribed radiolucent lesion can be seen by radiographic studies.

• Sinonasal chondromas appear as a polypoid, firm, smooth-surfaced nodule measuring usually from 0.5 to 2.0 cm and rarely greater than 3.0 cm.

• Histologically, these are lobulated tumors composed of chondrocytes recapitulating the normal histology of cartilage.

• Cellular pleomorphism, binucleate chondrocytes, or increased mitotic activity is not present.

• Conservative but complete surgical excision is the preferred treatment.

• Recurrences are uncommon.

Clinical

• In the head and neck two forms of myxomas/fibromyxomas are identified:

  • Facial skeletal–derived

  • Soft tissue–derived

Pathology

Differential Diagnosis

• Sinonasal inflammatory polyps

• Dental papillae (for intraoral lesions)

• Vocal cord polyps (for laryngeal lesions)

• Peripheral nerve sheath tumors

• Low-grade fibromyxoid sarcoma

• Sarcomas with myxoid component (e.g., myxofibrosarcoma, liposarcoma, rhabdomyosarcoma, others)

• Cartilaginous tumors:

  • A separate and distinct benign tumor of cartilaginous origin that may involve the craniofacial and paranasal sinus bones is the chondromyxoid fibroma ( Fig. 3-33 ):

    • –

      More common in men than in women; most common in the second to third decades of life

    • –

      Mandible is the most common site (symphysis or molar-retromolar area).

    • –

      Symptoms include pain, loosening of the teeth, difficulties in opening the jaws, and headaches.

    • –

      Radiographic appearance varies, depending on the involved bone, from round or oval; well-demarcated, radiolucent lesion usually measuring less than 5 cm in long bones to large, irregularly outlined lesions in flat bones.

    • –

      Histology is characterized by a lobular appearance with lobules separated by vascularized connective tissue and a zonal arrangement of the cellular component: center of the lobules are predominantly myxoid with scattered stellate-appearing cells; periphery of the lobules are more cellular, composed of cells with round to oval to spindle-shaped nuclei, an eosinophilic to amphophilic cytoplasm often with multipolar, stellate extensions

    • –

      FGF-23 expression reported in some cases of chondromyxoid fibroma (as well as aneurysmal bone cyst)

    • –

      With time, the myxoid areas may become fibrotic; presence of cartilage varies but never exceeds 75% of the total tumor volume; osteoclastic giant cells and calcifications may be seen.

    • –

      Surgery (en bloc resection) is the preferred treatment; local recurrences may occur if incompletely excised (curettage); malignant transformation in the absence of prior irradiation rarely occurs.

    

Treatment and Prognosis

• Conservative but wide local excision is the preferred treatment.

• These tumors tend to be slow-growing and usually follow a benign course but may have the potential for local destruction following inadequate excision.

• Recurrence or metastasis does not occur:

  • Metastasis from a presumptive sinonasal myxoma or fibromyxoma should seriously place that diagnosis in doubt and probably represents a myxoid variant of a sarcoma (liposarcoma, myxofibrosarcoma, or rhabdomyosarcoma).