Case Study – Painful Nodules on Thumb: What If It’s Not Rheumatoid Arthritis?

Patient and history

According to Katharina A. Kelber and her colleagues, a man complained of painful nodules on his left thumb that had existed for seven years and had grown. Based on histological examination after two external excisions, the diagnoses were made: rheumatoid nodule and benign fibrous histiocytoma, respectively. Treatment with hydroxychloroquine would not be effective.

Results of tests/examinations and diagnosis

• The entire thumb of the left hand is sclerotic, limited in movement, and there is ulceration at the base of the thumb.
• Histology: granulomatous tumor with necrosis, partially located in the helix, moderately polymorphic nuclei, positive for cytokeratins.
• Diagnosis: Combining clinical, histological and immunohistological aspects, the authors made a diagnosis of epithelioid sarcoma of the usual type.

Discussion

According to the authors, epithelioid sarcoma is very rare; the long-term prognosis is unfavorable. Both clinically and histologically, epithelioid sarcoma can mimic rheumatoid nodules and other granulomatous processes such as granuloma annulare or warts.

Other differential diagnoses in cases of epithelioid tumor cell phenotype include: malignant epithelioid peripheral nerve sheath tumor, amelanotic melanoma, epithelioid angiosarcoma, and carcinomas. Professor Thomas Mentzell, pathologist (Dermatopathologie Bodensee [Lac de Constance]) explains that rare variant forms of classic epithelioid sarcoma, such as proximal type epithelioid sarcoma, can pose particular challenges in the differential diagnosis.

Epithelioid sarcoma is the most common sarcoma of the hand and wrist and occurs more often in younger patients in the distal extremities, explain Katharina A. Kelber and colleagues. Men are affected twice as often as women. The tendency for recurrence is significant, especially for local recurrence; According to Thomas Menzel, approximately 70–85% of patients develop local recurrences. Distant metastases are possible.

The treatment of choice for localized lesions is complete resection with intraoperative irradiation, explain Katharina A. Kelber and colleagues. Intraoperative chemotherapy may be considered in selected cases for large tumors that are not completely resectable. For distant metastases, treatment usually includes anthracycline-based chemotherapy (especially in combination with ifosfamide) or gemcitabine and docetaxel. Pazopanib, a multikinase inhibitor, is the first targeted agent approved for patients who have already received metastatic chemotherapy or who have progressed within 12 months of (neo)adjuvant treatment. EZH2 inhibitor (zeste homolog 2 enhancer) tazemetostat also showed interesting results in metastatic epithelioid sarcoma.