Fine-needle aspiration cytology of chondroid syringoma of fore arm: Report of a rare case.

Chondroid syringoma is a rare benign adnexal tumor of sweat glands with microscopic resemblance to the salivary gland pleomorphic adenoma. Cytology is rarely utilized for preoperative assessment of these slow-growing, small, nodular lesions. Definitive cytological diagnosis is also quite difficult, and majority of the aspirates are evaluated as benign adnexal tumors leading to mandatory histopathological examination for pinpoint diagnosis. Here, we report a case of chondroid syringoma of forearm, which was diagnosed by cytology and also confirmed after histopathological examination. Pinpoint cytological diagnosis can help early formulation of necessary management protocol.

Introduction

Chondroid syringoma is a rare benign adnexal tumor of sweat gland origin.[12] It is also called benign mixed tumor of skin as it contains both epithelial and mesenchymal components.[12] Reported incidence of chondroid syringoma is 0.01-0.098% of all primary skin tumors.[13] The most common presentation is a small, slow-growing, subcutaneous nodular mass in the head-neck region.[134] Until now, only few cases of cytological diagnosis of chondroid syringoma have been reported.[12] Here, we are presenting a unique case of eccrine chondroid syringoma of forearm, diagnosed by fine-needle aspiration cytology (FNAC) and subsequently confirmed by histopathology.

Case Report

A 33-year-old male presented with a nodular swelling over left forearm for 1½ year. On examination, it was a firm to hard, nontender, mobile, subcutaneous mass measuring 2 cm × 1.5 cm. Overlying skin was thin and fixed with the mass without any ulceration. Fine-needle aspiration was done with 22G needle attached with 20 mL disposable syringe. Two passes were made from two different points for adequate aspirate. Aspirated material was thick mucoid. Smears were stained with Leishman-Giemsa stain.

On cytological examination, smears were moderately cellular comprising of clusters of round to oval cells and abundant chondro-myxoid ground substance. High power examination revealed two distinct types of cells in the smears. The epithelial cells were monomorphic, round to oval, medium sized having moderate amount of cytoplasm, bland round to oval nuclei with finely dispersed chromatin [Figure 1a and b]. Smaller myoepithelial cells having plasmacytoid appearance with dark nuclei were interpreted within clumps of epithelial cells [Figure 1a]. Smears were interpreted as chondroid syringoma and histopathology was suggested.

Figure 1

(a and b) Smears show tight clusters of benign round to oval epithelial cells and myoepithelial cells in fibrillary chondro-myxoid ground substance (Leishman–Giemsa stain, ×400)

On excision, the mass was encapsulated, partially covered with skin, firm to hard in consistency and measuring 2 cm × 1.5 cm × 1 cm. Cut surface of the tumor was solid, gray tan in color and without any necrosis or hemorrhage. On histopathological examination, the tumor was encapsulated with a large area of cartilaginous differentiation. The cellular areas were composed of cuboidal to polygonal cell nests or islands, irregularly distributed among abundant chondro-myxoid stroma [Figure 2]. The epithelial cells were also arranged in acinar and ductular pattern in some areas [Figure 2]. Histomorphology confirmed the cytological diagnosis of chondroid syringoma.

Figure 2

Section show epithelial cell clusters in tubules, ducts, cords and nests and chondro-myxoid stroma with an area of cartilaginous tissue (H and E, ×100)

Excision site was healthy during the postoperative period and no recurrence was observed after 6 months of follow-up.

Discussion

Nasse, first described a case of skin tumor containing both epithelial and mesenchymal components in 1892.[13] Hirsch and Helwig introduced the name chondroid syringoma and subsequently used as alternate to the term mixed tumor of skin.[235] Chondroid syringomas are defined as benign adnexal tumors containing both epithelial and mesenchymal elements with histological resemblance to benign mixed tumors of salivary glands.[6]

Chondroid syringomas commonly present as nontender, firm, nodular, subcutaneous or intra-cutaneous masses of 0.5-3 cm diameter.[57] Previous literature have recorded a male predisposition and wide age range of 20-80 years.[357] Though most of the cases involve head and neck areas, cases involving trunk, extremities, axillary and scrotal areas are also documented.[3578] In the present case, the lesion was located at dorsal surface of left forearm, relatively a rare location. Pailoor et al.[5] reported a case of cytological diagnosis of chondroid syringoma involving little finger. Chondroid syringomas are difficult to diagnose clinically because a wide range of nodular skin lesions simulate it such as, dermoid cyst, neurofibroma, dermatofibroma, pilomatrixoma, cutaneous histiocytoma and seborrheic keratosis.[179]

In the majority of the cases confirmatory diagnosis depends up on histopathological examination. Histologically chondroid syringomas can be categorized into two types - apocrine and eccrine, as classically described by Headington.[79] The apocrine types exhibit branching tubular pattern with cyst formation (tubulo-cystic), lined by double cell layers (cuboidal and flattened). Whereas eccrine types show single layer of cuboidal epithelial cells surrounded by chondro-myxoid stroma.[12] On immunohistochemistry, the inner cuboidal layer shows positive staining with epithelial markers like cytokeratin, whereas outer layer expresses mesenchymal markers such as vimentin, S-100 protein, neuron specific enolase and glial fibrillary acidic protein.[1710]

Though histopathology is a gold standard, FNAC can suggest a diagnosis of chondroid syringoma on the basis of thick mucoid aspirates exhibiting distinct biphasic cell population of epithelial and myoepithelial cells in a fibrillary chondro-myxoid stroma.[57] However sometimes, the aspirates may lack distinct biphasic cell populations or show predominantly monophasic cells, which create diagnostic difficulties.[710] Cytology is rarely applied for preoperative assessment of these nodular lesions. Even in cases undergoing aspiration, smears are, usually, interpreted as benign adnexal tumors without proper categorization. Previous literature have shown that accurate cytological diagnosis of chondroid syringoma is difficult. Still FNAC should be recommended to establish benign nature of the neoplasm and to differentiate from other common nodular skin lesions such as epidermal cyst, neurofibroma, cutaneous benign fibrous histiocytoma, etc.

Local excision with a cuff of normal tissue is desirable management in chondroid syringoma to avoid recurrence.[14] Follow-up for long duration at regular intervals is necessary to monitor recurrence. Malignant counterpart of chondroid syringoma is extremely rare, which may arise in a preexisting benign chondroid syringoma or may arise de novo.[710]

Conclusion

Fine-needle aspiration cytology can be used as a useful preoperative diagnostic tool for diagnosis of cutaneous and sub-cutaneous lesions. Diagnosis of chondroid syringoma can be possible by careful evaluation of a smear containing biphasic (epithelial and myoepithelial) cell population with chondro-myxoid fibrillary matrix in a mucoid aspirate obtained from a sub-cutaneous nodule. Present case is a good example of cytological diagnosis of chondroid syringoma with histopathological correlation, which will encourage future workers to utilize this simple, cost effective diagnostic procedure for preoperative definitive diagnosis of this benign neoplasm helping clinicians to formulate proper management protocol with reduction of postsurgical recurrences.