A spindle cell carcinoma presenting with osseous metaplasia in the gingiva: a case report with immunohistochemical analysis

Abstract

Background: Spindle cell carcinoma (SpCC) is a rare, high malignant variant of squamous cell carcinoma (SCC), which shows biphasic proliferation of conventional SCC component and malignant spindle shape cells with sarcomatous appearance.

Methods: A case of Spindle cell carcinoma with bone-like calcified materials, occurring at the mandibular molar region of 71-years-old Japanese male patient was presented with gross finding, histological findings and MRI image. To identify the characteristics of the bone-like materials, immunohistochemistry were performed.

Results: Histologically, the cancer cells were composed of spindle cells and epithelial cells which form nests with prominent keratinization. Histological findings showed typical histology of the SpCC, however, as an uncommon finding, spatters of calcified, bone-like materials were observed in between the cancer cells. Immunohistochemistry revealed that cancer cells were positive for cytokeratins and vimentin to a varying degree and negative for Desmin, S-100, Osteopontin, BMP-2 or BMP-4. These findings implied that the calcified materials were formed by metaplasia of the stromal cells.

Discussion: Bone-like materials formation by osseous and/or cartilaginous metaplasia of the stroma in the carcinoma has been reported. However, the detailed mechanism of these metaplasia and affection on the clinical feature, prognosis and therapies are not well established. In summary, we presented an unique case of SpCC, which has not been described in the literature.

Figure 1

Gross finding of the tumor. Intraoral examination showed exophytic, polypoid mass with irregular surface in the mandibular molar region.

Figure 2

Axial MRI imaging of the tumor. The margin of the lesion was clear, no invasion was observed.

Figure 3

Macroscopic image of the tumor. The lesion was a fragile mass with ulcerated surface. The cut surface was grayish-white in color, myxoid or lobular pattern in some areas.

Figure 4

Histological findings. (a) The cancer cells were composed of spindle cell component and epithelial component. (b) Transition of spindle cells into epithelial component was observed. (c) Conventional squamous cell carcinoma components presenting with keratinization were also observed. (d) Spatters of calcified materials with bone-like appearance were observed.

Figure 5

Immunohistochemistry. (a) Cytokeratin AE1/AE3 was positive both in spindle shape cells and epithelial nests. (b) Vimentin was only positive in spindle shape cell component, while it is negative in the epithelial nests. (c) Ki-67 index of the cancer cells was >30%. (d) The matrix of the calcified materials (arrows) showed positive reaction for osteopontin, while cancer cells did not.