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CLEAR CELL SARCOMA (MALIGNANT MELANOMA OF SOFT PART) PRESENTINGAS RECURRENT SCALP TUMOUR

Vikas S Kavishwar*, Ila M Vora**
*Lecturer in Pathology; **Prof. and Head of Pathology; TN Medical College, BYL Nair Hospital, Dr. AL Nair Road, Mumbai Central, Mumbai.

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Clear cell sarcoma is a rare malignant neoplasm usually presenting as soft tissue mass in foot of young adult. Ultrastructural studies reveal neuroectodermal origin with melanocytic differentiation. Thus it is considered as malignant melanoma of soft parts. Though the prognosis is apparently better as compared to the conventional melanoma, local recurrences and metastases are frequently seen. Large tumour size and extent of necrosis are factors for poor prognosis.

We report a case of clear all sarcoma presenting as recurrent scalp tumour.

INTRODUCTION

Clear cell sarcoma of tendons and aponeuroses is a rare and histologically distinctive malignant soft tissue tumour. [1] Many authors believe that these tumours are neuroectodermal in origin and are derived from deep melanocytic cells associated with tendons and aponeurosis. [2] The most common site is in the foot, often near the Achilles tendon or plantar aponeurosis. [3] We report a case of clear cell sarcoma with an unusual presentation as recurrent scalp tumour.

CASE REPORT

A nineteen year old male came with recurrent scalp swelling over left parietal region. The swelling was first detected at the age of ten years and was excised after eight months. Three years after that there was reappearance of similar swelling. He was operated again. However the swelling as mass measuring 5 x 3 x 2 centimeters. The previous histopahology reports were not available.

Examination revealed that the swelling was subcutaneous and adherent to overlying skin but free from the skull bones. It was soft to firm, mobile and non-tender. Wide excision of the mass with surrounding apparently normal tissue was carried out.

Specimen of skin covered soft tissue bit alongwith the mass was measuring 6 x 4 x 3 centimeters. The mass was non-encapsulated but well circumscribed and adherent to the skin flap. On cut surface it was whitish homogeneous in appearance and firm in consistency.

Histopathologically the tumour was seen in the dermis (Fig. 1) and subcutaneous tissue. The cells were arranged in solid nests and trabeculae separated by fibrocollagenous tissue. The cells were large polygonal with abundant cytoplasm and vesicular nuclei (Fig. 2). Focal areas of clear cell change were also seen. The nuclei showed moderate pleomorphism with occasional prominent nucleoli and two to three mitotic figures per ten high power fields. The provisional diagnosis was poorly differentiated sarcoma and tissue was subjected for further studies.

Immunohistochemical profile revealed positivity forvimentin and S-100 (Fig. 3). Other markers like cytokeratin, epithelial membrane antigen, myoglobin, desmin and SMA were negative. On electron microscopy, the cytoplasm was packed with mitochondria, rough endoplasmic reticulum, lipid vesicles and few oval dense granules resembling premelanosomes. Thus both immunohistochemistry and electron microscopy pointed to the diagnosis of clear cell sarcoma of tendon sheath and aponeurosis.

Fig. 1 : Section showing tumour tissue in dermis. (H and E x 40).

 

Fig. 2 : Section showing polygonal tumour cells arranged in nests the cell show large nuclei and vacuolated cytoplasm (H and E x 40).	Fig. 3 : Section showing cytoplasmic positivity of tumour cells for S-100 protein. (S - 100 immunostaining x 100)

DISCUSSION

Clear cell sarcoma usually presents as painless, gradually enlarging mass in young adult3 as seen in our case. Though foot is the most common site, the neoplasm has been described in ankle, knee, thigh and other sites including penis. [4] Tumour in scalp is a rare presentation.

Grossly the tumour is usually firm, well circumscribed, grayish white and has a gritty sensation on cutting. [5] Microscopically, solid nests and fascicles of pale fusiform or cuboidal cells are present as seen in this case. Presence of multinucleated giant cells and abundant iron deposits have been described.[5]

In many cases the tumour cells contain cytoplasmic melanin. [2], [6] Even if melanin is not demonstrable by light microscopy, melanosomes [7] and S-100 protein [8] are present in almost all cases. Immunoreactivity for HMB - 45, leu - 7, NSE and vimentin has been described. [2], [8] Thus clear cell sarcoma represents a peculiar type of malignant melanoma of soft parts. [2]

As compared to conventional melanoma of skin metastatic to soft tissue; clear cell sarcoma shows lesser degree of aneuploidy. [9] The tumour is associated with chromosomal translocation t(12,22)(q13, q12). [10] It is interesting that the same gene is also affected in Ewing’s sarcoma, PNET and intra-abdominal desmoplastic small round cell tumour. [5]

The prognosis is relatively poor and local recurrences as seen in this case are quite frequent. [1] Unlike most other sarcomas, spread to regional lymphnode is common, occurring in about 30% of cases. [3] Metastatic spread has been reported in around 65% of patients and large tumour size alongwith degree of necrosis are predictors of poor prognosis. [11,12]

ACKNOWLEDGEMENT

We will like to thank Dr. (Mrs.) Soman and her colleagues from Dept. of Pathology, Tata Memorial Hospital, Parel, Mumbai for their kind help in immunohistochemistry and electron-microscopy of this case.

REFERENCES

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