Clear cell sarcoma (CCS) was first described by Dr. Franz Enzinger in 1965. It is a rare type of soft tissue tumor that constitutes approximately 1% of all sarcomas [1]. CCS primarily occurs in deeper soft tissues near tendons and aponeuroses of distal extremities and is often misdiagnosed. It is thought to arise from neural crest cells within the soft tissue. It is a distinct entity characterized by the presence of the EWS-ATF1 fusion transcript [2]. Although CCS predominantly affects adolescents and young adults with a similar incidence between males and females, its true frequency remains unknown [3].
We report a case of CCS in an adolescent male, which was clinically misdiagnosed as cutaneous lymphoma.
A 20-year-old-male presented to our outpatient department with complaints of mild fever since 5 months and multiple swellings all over the body in both upper and lower limbs, chest, and back along with pain abdomen. The swellings were gradually progressing in size, with mild pain and itching. On examination, he had cervical and bilateral axillary lymphadenopathy (right>left), and multiple mobile swellings all over the skin, the largest measuring approximately 3 cm (Figure-1A, B). There was no history of weight loss.
An outside biopsy from one of the lesions was reported as high-grade large cell Non-Hodgkin Lymphoma involving the deep dermis. Based on this presentation, the clinical diagnosis was deemed as Lymphoma, favoring cutaneous T cell lymphoma.
On PET CT scan, he showed multiple FDG avid lymphadenopathy in right cervical level II, left cervical level I/IV nodes, bilateral axillary nodes (SUV max 6.45), mediastinal nodes (bilateral upper paratracheal, prevascular, right pulmonary ligament, left epiphrenic), abdominal nodes, right obturator node, and right inguinal node. Hypermetabolic multiple intermuscular, intramuscular, cutaneous, abdominal and pelvic deposits were identified. FDG avid foci were also noted in the left femur, lung, and bilateral suprarenal region (Figure-1 C, D).
The previous biopsy was reviewed in-house. It revealed multiple fragmented tissue pieces infiltrated by diffuse sheets and nests of malignant cells having plasmacytoid morphology. Individual cells had eccentrically placed nuclei, vesicular chromatin, conspicuous to prominent nucleoli and a moderate amount of eosinophilic cytoplasm. Focal areas of necrosis were also noted. Few places showed perivascular arrangement of tumor cells resembling papillae. Good number of tumor giant cells and cells having bizarre nuclei were also noted (Figure 2).
The main differentials based on the morphology of the tumor cells included cutaneous lymphoma especially Anaplastic large-cell lymphoma, Plasmacytoma and malignant melanoma.
Other differentials considered were metastatic poorly differentiated carcinoma, Langerhan’s cell histiocytosis.
On first panel of immunohistochemistry, atypical cells were focally positive for CD138, while negative for PanCK, CD30 and CD45, thus ruling out carcinoma and lymphoma. On further evaluation tumor cells were diffusely positive for HMB-45, S-100, Melan-A, and SOX-10 while focal positivity was noted for CD56 and CD99. Atypical cells were negative for EMA and CD1a. Ki-67 proliferative index was approximately 65% (Figure 3 and 4).
Since the multiple subcutaneous lesions were not associated with the overlying skin, we rendered the diagnosis of clear cell sarcoma of the soft tissue.
The patient was advised to undergo EWSR1 rearrangement studies, which was done outside, came out to be positive, confirming the diagnosis of clear cell sarcoma.