Asymptomatic nodule on lip

Diagnosis: Chondroid syringoma, apocrine type (apocrine mixed tumor) [Figure - 2] shows an epithelial neoplasm with abundant basophilic chondroid stroma and mucin. The epithelial component is made up of elongated and branched tubules lined by a double layer of epithelium [Figure - 3]. Some of the tubules show decapitation of secretion indicating their apocrine nature [Figure - 4].

Discussion

Chondroid syringoma, also called mixed tumor of the skin is a benign epithelial neoplasm with secondary changes in the stroma. It is common during the fourth to sixth decade of life. It is twice as common in males as in females. It is usually located on the face, scalp and neck as a solitary firm intradermal or subcutaneous nodule, 0.5 to 3 cm in diameter.[1] The overlying skin is attached to the tumor mass but is usually normal in texture and color.

Histopathologically these tumors are noncapsulated and sharply circumscribed. Tumor mass consists of variable admixtures of two components, epithelium and chondroid or myxoid connective tissue. Based on the characteristics of the tubules or lumina, two types of chondroid syringoma are known: one shows elongated and wide, tubular and cystic, partially branching lumina and the other small, tubular, monomorphous nonbranching lumina.[2]

These tubules may show apocrine or eccrine differentiation.[2] The first type is usually lined by a double layer of cells, inner cuboidal and outer flattened. The inner layer may be sometimes columnar and shows apocrine secretion. While the second type is lined by a single layer of cells without apocrine secretion.[2] The stroma shows abundant mucoid material. Due to shrinkage of the mucoid matter, fibroblasts and epithelial cells are surrounded by a halo giving a chondroid appearance.[3]

Chondroid syringomas are called mixed tumors of the skin because they frequently contain other epithelial or stromal elements. An epithelial element that may occur within these neoplasms are follicular structures with variable differentiation.[4] Nonepithelial elements occasionally seen within mixed tumors are fat cells, mucin or true cartilage.

These tumors usually grow slowly for many years. Simple excision is the only treatment. Recurrences are common unless complete excision is carried out. Malignant change is very rare.