Histopathology:
The Hematoxylin and eosin stained sections revealed superficial stratified squamous epithelium and underlying connective tissue. The lesion appeared to be well encapsulated(Figure 8E). Focal areas of connective tissue stroma was myxomatous (Figure 8C), collagenous and hyalinized. Areas of spindle and stellate shaped fibroblastic cells (Figure 8D) and atypical, hyperchromatic, fusiform chondroblastic cells proliferation (Figure 8A), bizarrely shaped mitotic figures along with adjacent malignant osteoid tissue was evident (Figure 8B). Osteoid was scanty and immature. Chondroblastic proliferation was dominant and aggressively proliferating with areas showing pleomorphism. Hence, histopathological diagnosis of chondroblastic osteosarcoma was made.
Discussion: Osteosarcomas are difficult to diagnose even with immunohistochemistry and advanced radiography as single lesion may show osteoid in one region along with scattered chondroid, myxoid, fibrous areas. Superficial layers may show benign fibrous growth with epithelial hyperplasia which is the most common site of biopsy. Such diversity of histopathology in various areas of lesion pose a challenge to surgeon to procure representative biopsy specimen. When suspecting a osteosarcomatous lesion surgeon should prefer deeper hard tissue biopsies preferably the hard tissue growing beyond the confines of cortices. These sites are more representative of actual pathology rather than superficial fungating tumour mass which is comparatively easier to excise.
In this case final histopathology of excised hard tissue specimen was confirmative of very rare mixed form of chondrogenic osteosarcoma. The role of neo-adjuvant chemotherapy in chondroblastic osteosarcoma is limited to tumour mass shrinkage and to achieve negative tumour margins7. But due to its rapid metastasis, before definitive surgery patient was advised neo-adjuvant chemotherapy with doxorubicin 80 mg and cisplatin 140 mg, but even after 2 cycles there was no considerable decrease in size of tumour mass which was in accordance with chemoresistance mechanisms in osteosarcoma. Altered deoxyribonucleic acid (DNA) repair activity8, overexpression of resistance-related proteins such as metallothioneins, glutathione-S-transferase π, heat shock protein 27, and lung resistance-related protein9 and alterations in cell cycle10 are the probable factors for chemoresistance.
As definitive surgery patient underwent right side supra-omohyoid neck dissection and right hemi-mandibulectomy(Figure 9) followed by reconstruction with anterolateral thigh flap(Figure 10,11) in Department of Surgical Oncology. Following which patient was referred to radiotherapy.
Low and intermediate grade osteosarcomas are juxtacortical, medullary or periosteal in nature. Whereas aggressive high grade osteosarcomas are classified by World Health Organization (WHO) in 4 histopathological types as per predominance of tissue found. Osteoblastic, chondroblastic, fibroblastic and small cell types as the name suggests show predominance of respective tissue. Yet another telangiectatic form is also described in the literature11.