Undifferentiated pleomorphic sarcoma: Diagnosis of exclusion

Introduction

Undifferentiated pleomorphic sarcomas are aggressive tumors, commonly seen in adults. However histopathological pattern is very much variable in these soft tissue malignant neoplasms. We detected this case where proper clinico-histomorphological analysis coupled with immunohistochemistry (IHC) helped us to arrive at a diagnosis.

Case Report

A 70-year-old male presented with swelling over the posterior aspect of the left thigh. Swelling was gradually increasing in size.

Magnetic resonance imaging findings revealed a well-defined altered signal intensity lesion with central area of necrosis in muscular plane of posterior aspect of left mid aspect of thigh involving lateral fibers of biceps femoris.

The patient was subjected to fine needle aspiration cytology [FNAC], the findings of which were suggestive of a soft tissue sarcoma.

Excision of the mass was done and was submitted to us for histopathological examination.

On gross inspection, soft-tissue mass measured 12 cm × 5 cm × 4 cm, with tumor mass of about 3 cm × 2 cm × 1 cm dimensions.

Cut section was gray brown with areas of necrosis in it Figure 1.

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Figure 1

Cut section of the tumor mass

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Histopathological examination revealed a malignant tumor with pleomorphic bizarre cells. At places, spindled and tadpole like contour cells were seen. Many histiocytic giant cells were also noted in the sections Figure 23. The surgical margins were free of the tumor.

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Figure 2

H- and E-stained section from the tumor showing histiocytic cells

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Figure 3

Undifferentiated pleomorphic sarcoma: showing anaplastic and variable cellularity

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Based on these microscopic findings and the site involved, differentials of pleomorphic rhabdomyosarcoma and an undifferentiated pleomorphic sarcoma were kept. Considering variable histomorphological features, immunohistochemistry (IHC) was suggested.

Immunohistochemistry

IHC showed CD68 and S-110 protein expression in the histiocytes and histiocytic giant cells.

Tumor cells were immunonegative for smooth muscle actin (SMA), desmin S-100 protein, CD34, CK, epithelial membrane antigen, CD68, and glial fibrillary acidic protein (GFAP).

However, no photographs of IHC panel could be obtained as the patient got it done from different institutes.

Comparing all these findings, a concluding diagnosis of high-grade undifferentiated pleomorphic sarcoma was made. Moreover, the patient was referred for oncotherapy line of management.

However, nearly 2½ months later, the patient reported back with a recurrent painful lesion which was excised again.

Pathological findings showed similar gross and microscopic features as the initial lesion Figures 45.

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Figure 4

Gross morphology of the recurrent lesion

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Figure 5

Microscopic features in a recurrent lesion (H and E)

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On attempts to know the follow-up, we got the information that the patient had succumbed to the disease, and cause of death informed to us was multiorgan failure.

Discussion

Undifferentiated pleomorphic sarcomas have high incidence of local recurrence and metastasis.¹

Accounting for <5% of adult soft-tissue sarcomas,² these neoplasms have also been reported in children.³

Individuals in the age group of 50–70 years are mostly affected with common site being the lower extremities.⁴ However, there have been reports of other rare sites involved by these neoplasms such as retroperitoneum⁴ male breast,⁵ mediastinum,¹ cutaneous,⁶ and pelvic region.⁷

Conclusion

These undifferentiated sarcomas are tumors which do not show distinct line of differentiation and obvious morphological features on histopathology. complete workup is recommended to exclude other soft –tissue sarcomas and classify the lesion into this renamed high grade entity.⁸