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The clues for such diagnosis in this case are:
· Age : 45 mean age (40)
· Sex : male > female
· Site: carotid ……………..around sphenopalatine area
· Low power: lobular pattern of growth with Chondroid, hyaline and mucoid appearance separated by fibrous tissue
· High power: physaliphorous cells, no mitotic figures, mild pleomorphism ( plus absence of other features of other differential diagnoses……………see below)
· Immunohistochemistry was done and it is found to be positive for pan-cytokeratin, EMA and S-100
Detailed comment
CHORDOMA
Definition: Chordomas are currently divided, microscopically, into conventional, chondroid, and "dedifferentiated" subtypes.
CONVENTIONAL CHORDOMA
They are malignant, slowly growing neoplasms that occur along the axial skeleton, in the region of the embryonic notochord, particularly at its caudal and cranial extremes.
General Features
Chordomas of all types are uncommon neoplasms, accounting for only about 1 to 4% of malignant osseous tumors. They only arise along the spinal axis where the developing notochord and its remnants may be found. Conventional chordomas resemble fetal notochord microscopically, and are probably derived from notochordal remnants or a common precursor. One study, however, noted some histochemical differences between fetal notochord and chordoma. Purported chordomas occurring outside of the spinal axis are myxoid chondrosarcomas
Clinical Features.
Chordomas occasionally occur in children and young adults, although they are uncommon before the age of 30 years, and most patients are in their fifth to seventh decades of life. Spheno-occipital lesions tend to manifest about a decade earlier than those arising in the sacrococcygeal region, and are most common in the third to fifth decades of life. There is approximately a 2 to 1 male to female ratio.
Signs and symptoms of chordomas are closely related to tumor location.
Because of their usually slow growth, symptoms have often been present for more than a year. Spheno-occipital chordomas involve contiguous structures at the base of the brain. Most common symptoms include headache, cranial nerve palsies, especially diplopia and visual field disturbances, and signs of endocrine dysfunction due to pituitary compression. About 25% of patients have an intranasal mass resulting in discharge or obstruction. Cervical vertebral lesions produce spinal cord compression. Sacrococcygeal chordomas may produce insidious lower back pain, often with referred pain to the hip, knee, or groin, bladder or anorectal dysfunction, paresthesias, or a mass. In women, the symptoms may mimic a gynecologic malignancy.
Sites.
The sharp localization of chordoma to the spinal axis is well documented. This most cranial portion of the notochord is the site for about 37% of chordomas. About 50 % arise in the sacrococcygeal region and the remaining 13% involve the vertebrae, almost half of these in the cervical region.
Radiographic Appearance.
Radiographically, chordomas expand and destroy bone with frequent extracortical extension. Spheno-occipital lesions usually erode the clivus, sella turcica, and portions of the petrous and sphenoid bones. Intralesional calcifications are present in about 14% of typical (nonchondroid) sphenooccipital lesions, but are uncommon in vertebral chordomas. Magnetic resonance imaging or computed tomography may be of value in outlining the extent of disease.
Gross Findings.
Grossly, chordomas are multilobated, soft, myxoid, gelatinous masses. Their appearance may mimic that of a chondrosarcoma or even a mucinous adenocarcinoma. The soft tissue margins can appear deceptively discrete, or even encapsulated, but the tumor often extends beyond these grossly visible boundaries. The soft tissue component may be covered by a layer of periosteal bone that has remained intact due to the slow growth of the lesion. Intraosseous margins are usually less distinct.
Microscopic Findings: Microscopically, the hallmarks of chordoma are a lobular architecture, vacuolated (physaliphorous) cytoplasm, and a mucoid matrix s. Chordomas possess a wide spectrum of histologic appearances, however, and the classic physaliphorous cells may not be a dominant component. The lobules are separated by fibrous septa and contain cells arranged haphazardly, or in cords, columns, sheets, or trabeculae. Some cells have eosinophilic, nonvacuolated cytoplasm ; others contain single, large vacuoles, imparting a signet ring appearance; and still others are the prototypical multivacuolated or bubble-like cells. Large lakes of extracellular mucin containing hyaluronidase-resistant, sulfated mucopolysaccharides may surround the neoplastic cells. Nuclear pleomorphism is usually mild, and mitotic figures are typically nonexistent to rare. Most authors have been unable to attribute any prognostic importance to these variations.
Differential Diagnosis.
Metastatic Adenocarcinoma.
If a chordoma contains large numbers of cells with single cytoplasmic vacuoles, it may be confused with a metastatic signet ring adenocarcinoma. Immunohistochemical stains or ultrastructural examination can compound the confusion, because chordomas express epithelial cell markers such as keratin and epithelial membrane antigen and also contain tonofilaments and desmosomal cell attachments. Careful histologic study will usually allow distinction. Gland formation is not seen in chordomas, and physaliphorous cells are lacking in adenocarcinomas. If necessary, mucin stains may be of value. Chordomas contain acid sulfated mucin that is colloidal iron positive and resistant to hyaluronidase predigestion. The mucin in signet ring adenocarcinomas is of the neutral, epithelial type and will stain with the periodic acid-Schiff stain. Mucicarmine will stain adenocarcinomas, but may also be positive in some chordomas.
Liposarcoma.
The vacuolated cells in chordomas may rarely be mistaken for the lipoblasts of a liposarcoma. The lobular growth pattern of chordoma, and the presence of evenly scattered physaliphorous cells should distinguish the two. Problematic cases may require special stains. The mucin in myxoid liposarcoma is nonsulfated and hyaluronidase sensitive. A fat stain also may be helpful, as lipid is not found in chordomas. Epithelial markers such as keratin or epithelial membrane antigen are not found in liposarcoma, however, both tumors will be positive for S-100 protein.
Myxoid Chondrosarcoma.
The mesenchymal neoplasm most likely to be confused with chordoma on purely histologic grounds is myxoid chondrosarcoma.
These tumors may arise in the soft tissues or bones, but they predilect the extremities, and are rare in the axial skeleton. Their lobular architecture, cord-like arrangement g241 of cells, and myxoid stroma are quite similar to chordoma. Physaliphorous cells are lacking, however, and the cells typically have less pleomorphism than those of chordoma. Immunohistochemical studies also distinguish these entities. The cells of chordoma are typically positive for cytokeratin and epithelial membrane antigen, and negative for lysozyme.
The reverse staining pattern is seen in myxoid chondrosarcoma. Both tumors may express S-100 protein. Whereas skeletal myxoid chondrosarcomas are invariably negative for epithelial markers, some soft tissue tumors of this type, sometimes labelled "chordoid sarcomas," may express epithelial membrane antigen, but not cytokeratin.
Polyvinylpyrrolidone Granuloma.
This unusual reactive lesion may create a histologic image indistinguishable from that of chordoma.
Polyvinylpyrrolidone (PVP) is a hydrophilic macromolecule that has been used as a plasma substitute, and as a retardant in some injectable drugs. The high molecular weight of some PVP molecules prevents their renal excretion and leads to accumulation in histiocytes. Mass lesions may form in the soft tissues, presumably at injection sites, that are composed of histiocytes filled with bubbles of PVP. These cells closely mimic the physaliphorous cells of chordoma. Special stains aid in the distinction. PVP stains strongly with Congo red, Sirius red, Sudan black B, Fontana-Masson, Victoria blue, luxol fast blue, colloidal iron, Gomori methenamine silver, and mucicarmine, and negatively with periodic acid-Schiff, Alcian blue at pH 1.0, 2.5, or 4.0, and techniques for iron
Treatment and Prognosis.
Because complete excision is seldom possible, local recurrences are common and account in large part for the high mortality. In one series of 36 patients, the mean survival was 4.1 years, and only one patient lived longer than 10 yearse. The role of flow cytometry as a prognostic factor is being evaluated.
In one study, most (73 %) of conventional chordomas were diploid neoplasms, limiting the value of this technique. Two of eight patients with diploid neoplasms were disease free, one died of disease, and five were living with disease. Of the three patients with aneuploid conventional chordomas, two had died of disease and one was living with disease.
Wide surgical excision at the time of initial presentation offers the best chance for cure. Recurrent lesions can almost never be completely eradicated.
Optimal treatment for unresectable disease appears to be generous surgical debulking, coupled with adjuvant radiation therapy. Cryosurgery has also shown promise in selected cases. Chemotherapeutic agents have not been effective. Between 5 and 43 % of patients develop metastatic disease, mainly in the skin and subcutaneous tissue, bones, lungs, and lymph nodes. Cutaneous metastases are frequently mistaken for dermal mixed tumors.
CHONDROID CHORDOMA
Definition. A variant of conventional chordoma that includes foci of cartilaginous differentiation.
General Features.
Falconer et al initially described chondroid chordoma in 1968, and the lesion was further documented by Heffelfinger and colleagues several years later. Chondroid chordoma is a clinicopathologically important neoplasm occurring almost exclusively in the spheno-occipital region with rare reports of apparent sacrococcygeal cases. In the spheno-occipital region, it is about one third as common as conventional chordoma.
The exact nature of chondroid chordoma has been the subject of controversy. Some authors doubt whether chondroid chordoma is distinguishable from chondrosarcoma. Histochemical and immunohistochemical studies have suggested that the chondroid portions of these lesions are intrinsically cartilaginous However, ultrastructural features have been said to more closely approximate those of conventional chordoma.
With rare exception, most recent studies have demonstrated that the "chordoid" portion of chondroid chordoma, immunohistochemically indistinguishable from conventional chordoma, supporting the argument that these are distinctive variants of chordoma with focally cartilaginous features.
Microscopic Findings
The distinctive microscopic characteristic is the presence of chondroid differentiation, in close proximity to zones of more conventional chordoma. The cartilaginous tissue possesses cells within lacunae separated by a stroma of hyaline cartilage.
The chondrocytes may be minimally atypical, as in an enchondroma, or moderately pleomorphic, simulating a low-grade chondrosarcoma. The proportion of cartilaginous tissue ranges from scant to predominant. Even a single microscopic focus of clear-cut cartilaginous differentiation appears to be sufficient to place the neoplasm in this prognostically more favourable subgroup.
Differential Diagnosis.
There are two potential pitfalls associated with these tumors, depending on the amount of chondroid material present. If the chondroid component is a minor element, it may be missed on limited sampling or overlooked on cursory microscopic examination. Alternately, if the majority of the tumor is cartilaginous, the chordoma element may be overlooked, leading to a misdiagnosis of chondroma, osteochondroma, or low-grade chondrosarcoma. To avoid these problems, all chordomas and cartilage-containing lesions arising in the spheno-occipital region should be completely sectioned and carefully examined microscopically.
Treatment and Prognosis:
Local recurrences almost invariably develop and account for the very high long-term mortality. Unlike conventional chordoma, however, survival is markedly prolonged.
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