Pathology of Chondroid Syringoma (Mixed Tumour of the Skin)

Pathology of Chondroid Syringoma

Dr Sampurna Roy MD 2023

Answer - Chondroid Syringoma (Mixed Tumor of Skin)

Chondroid syringoma represents the cutaneous counterpart of mixed tumor ("pleomorphic adenoma") of salivary glands, therefore it is also termed 'mixed tumour of the skin'.

The cutaneous lesion has different behaviour in that it rarely recurs even if inadequately excised.

It is generally accepted that there are both eccrine and apocrine variants of mixed tumour of skin.

Age:

Usually occurs in middle aged and elderly patients.

Common sites:

Head and neck region and rarely in the distal extremities.

Clinical presentation:

The tumour presents as a solitary, slow growing nodule (0.5 - 3 cm in diameter).

Microscopic features: Dermatopathology Quiz Case No 62

Well circumscribed tumour located in the dermis and subcutaneous tissue ; No epidermal connection with the overlying epidermis. ;

Tumour consists of epithelial component set in a chondroid, myxoid and fibrous stroma ;

There are epithelial nests, islands, ducts and tubular structures ;

Tubules or lumina may be:

(i) Large, multilayered, or complex structures.

(ii) Small relatively round tubules or simple tubules.

Focal areas of apocrine secretion may be present ;

In rare cases there are intracytoplasmic lumina of eccrine type;

Some cases show follicular and sebaceous differentiation (shadow cells, other elements of hair follicles and sebocytes) ;

Other features include: Keratinous cyst formation ; Presence of eosinophilic globules (collagenous spherulosis);

Islands of squamous epithelium ; Areas of ossification.

Immunohistochemistry:

Epithelial cells are Carcinoembryonic antigen (CEA) and cytokeratin positive;

The outer layer of ductal cells (myoepithelial cells) are S100 protein positive.

Hyaline cell-rich chondroid syringoma :-

Histopathological features:

Lobulated neoplasm composed of hyaline cells with plasmacytoid features showing ovoid nuclei, with occasional invaginations, finely granular chromatin, and discrete nucleoli; the cytoplasm is deeply eosinophilic with occasional dot-shaped paranuclear hyaline inclusions ; Hyaline cells might possess an aberrant myoepithelial differentiation;

Immunohistochemistry: Hyaline cells are strongly and diffusely positive for S-100 protein, pan and high molecular weight cytokeratins.

Cells are focally positive for GFAP, neuron-specific enolase, and cytokeratin 14.

Differential diagnosis: Malignant melanoma and extra-skeletal myxoid-chondrosarcoma.

Atypical mixed tumours:- Borderline features of malignancy characterized by an infiltrative margin, satellite tumour nodules, and tumour necrosis . These tumours do not metastasize.

Malignant chondroid syringoma:- A few cases have been reported;

More common in women ;

Occurs most often in trunk and extremities ;

May metastasize to both the regional and distant lymph nodes, causing the death of the patient. In these cases, radiation therapy follows the surgical excision.

Microscopic features: Lobulated appearance ;

Composed of epithelial and mesenchyme-like component (myxomatous and cartilaginous areas) ;

Epithelial component predominates at the periphery of the tumour;

Mesenchymal component is at the center;

Scattered mitoses ; Variable pleomorphism.

Immunohistochemistry: Positive staining for cytokeratin, S-100 protein, neuron- specific enolase and glial fibrillary acidic protein.