Orbital Chondroma: A rare mesenchymal tumor of orbit.

While relatively common in the skeletal system, cartilaginous tumors are rarely seen originating from the orbit. Here, we report a rare case of an orbital chondroma. A 27-year-old male patient presented with a painless hard mass in the superonasal quadrant (SNQ) of left orbit since 3 months. On examination, best-corrected visual acuity of both eyes was 20/20, with normal anterior and posterior segment with full movements of eyeballs and normal intraocular pressure. Computerized tomography scan revealed well defined soft tissue density lesion in SNQ of left orbit. Patient was operated for anteromedial orbitotomy under general anesthesia. Mass was excised intact and sent for histopathological examination (HPE). HPE report showed lobular aggregates of benign cartilaginous cells with mild atypia suggesting of benign cartilaginous tumor - chondroma. Very few cases of orbital chondroma have been reported in literature so far.

Chondroma is a benign cartilaginous tumor. Theoretically, a chondroma should not occur in membranous bones such as those of the orbit. Only the body and lesser wing of the sphenoid bone have any notable derivation from cartilaginous precursors, and the trochlea is the only purely cartilaginous structure in the orbit. Chondromas are usually asymptomatic except for either a palpable or visual mass, but sometimes increase in the size can lead to ptosis and proptosis. After complete resection, the patient should be followed up and watched carefully for malignant degeneration though the rate of malignant transformation in solitary chondroma is still controversial.

Case Report

A 27-year-old male patient presented to us with painless hard mass in superonasal quadrant (SNQ) of left orbit for 3 months which had progressively increased in size during 1-month associated with drooping of upper lid of left eye for 20 days [Fig. 1]. The patient has no significant past, personal, systemic and family history.

Figure 1

Photograph of patient showing visible mass at superonasal quadrant of left orbit

On examination, best corrected visual acuity was 20/20 in both eyes. Intraocular pressure in both eyes was OD-13 and OS-14 by Perkins applanation tonometer. Anterior segment and posterior segment of both eyes were normal except for approximately 2 mm downward and 2 mm outward dystopia of left eyeball. Full movements of both eyeballs were noted. Exophthalmometry of both eyeballs measured by Hertel's exophthalmometer were OD-14 mm and OS-15 mm and interpuppilary distance was 62 mm.

Computerized tomography scan report showed approximately 13 mm × 14 mm sized well defined minimally enhancing soft tissue density lesion in SNQ of left orbit. The lesion was found in extraconal compartment causing downward and outward displacement of the left eyeball. Scalloping and erosion of the lateral wall of left frontal sinus were noticed [Fig. 2].

Figure 2

Approximately 13 mm × 14 mm sized minimally enhancing soft tissue density lesion in superonasal quadrant of left orbit on computerized tomography plates. Note scalloping and erosion of lateral wall of left frontal sinus

Patient was operated for left-sided anteromedial orbitotomy through lid crease approach under general anesthesia. Though mass was found to be adherent to the bone, it was separated in toto by blunt dissection and sent for histopathological examination. Intraoperative and postoperative course were uneventful.

On gross examination, mass was a well-circumscribed nodule measuring 1.5 cm × 1.8 cm, having glistening white multilayered appearance [Fig. 3]. Microscopical examination revealed a multilobulated lesion composed of cytologically benign appearing spindle cells. The tissue was composed of round to ovoid nuclei in lacunar spaces suggesting cartilaginous differentiation with little pleomorphism and no mitotic figures [Fig. 4]. Immunohistochemical studies were positive for S-100 protein consistent with a cartilaginous tumor and for vimentin, consistent with a mesenchymal lesion, suggesting benign cartilaginous tumor - chondroma. Patient was symptomatically better 1 moth post operatively [Fig. 5].

Figure 3

Gross specimen of resected mass

Figure 4

Hematoxylin and eosin stained slide photograph showing mature chondrocytes in lobulated manner

Figure 5

Photograph of patient after 1-month

Patient was advised to follow-up after 6 months or in case of recurrence of symptoms.

Discussion

Chondromas of head and neck are extremely rare with an estimated 10% occurrence in this region.[1] The sites of predilection in the head and neck region include ethmoid sinus (50%), maxilla (18%), nasal septum (17%), hard palate and nasopharynx including sphenoid sinus (6% each), and alar cartilage (3%).[1] Though chondroma belongs to cartilaginous structure, it can develop from the nest of growth plate cartilage that have become entrapped in the medullary canal and lead to hamartomatous proliferation later on. Orbital chondromas are fairly distributed throughout all age groups; however, incidence occurs most frequently in the third and fourth decade with no sex predilection.

Garrity and Henderson[2] and Shields et al.[3] had reported only one case out of 1373 and 627 total mesenchymal orbital tumors respectively. Study of the incidence of primary orbital bone tumors conducted by Rootman and Connellet al.[4] revealed only one case of chondroma out of 62 primary orbital bone tumors over a period of 24 years.

Overall, the incidence of chondroma peaks during the sixth decade of life.[5] However, in the facial skeleton, chondroma generally occurs during adolescence and early adulthood as seen in our case.[6] Faber et al.[7] and Pasternak et al.[8] also reported orbital chondromas in 19-year-old male and 25-year-old woman respectively. However, Harrison et al.[9] has also reported an orbital chondroma in 9-year-old boy.

Recognizing a chondroma as a benign lesion can be challenging. According to Batsakis et al.,[10] histopathological distinction between a chondroma and a low grade chondrosarcoma is notoriously difficult as many of the fine structural features of low-grade chondrosarcoma cells are also found in cells of normal hyaline cartilage. Spjut et al. (1970) pointed out that because of many of the well-differentiated tumors were erroneously diagnosed as benign cartilaginous neoplasms, multiple blocks from cartilaginous tumors should be examined since areas diagnostic of chondrosarcoma may be noted only focally.

Chondrogenic tumors of the facial skeleton also show aggressive behavior. Because of the discrepancy between the histological picture and biologic behavior, chondrogenic neoplasm should be considered potentially malignant.[11] Hence wide surgical excision should be considered as the treatment of choice. Benign cartilaginous tumors are radio resistant, but radiotherapy may be offered for the treatment of primary and recurrent malignant cartilaginous tumors.

As chondroma has a tendency to sarcomatous change, even in histopathologically proven benign tumors a long-term follow-up is strongly advised. The prognosis of such tumors is good, and recurrence is uncommon with appropriate treatment.[12]