Syringoma
Histopathology:
– The dermis shows small, rounded nests (orange arrow) and few compressed angulated (coma/tadpole-shape) tubular ducts (coma/tadpole-shape) (red arrow) and cord-like structures (blue arrow), in a dense collagenised-fibrotic stroma.
– Some of the tubules show small lumen filled with pale eosinophilic material (green arrow). Tubules show inner bland cuboidal and peripheral myoepithelial cells layer. Cuboidal cells are polygonal with bland nuclear chromatin and pale eosinophilic cytoplasm.
– Keratin filled horn cysts are not seen. Cytologic atypia including nuclear hyperchromasia, prominent nucleoli, mitoses, or necrosis are not seen.
Practical Points of Pathoclinics:
- Syringoma is a benign ductal proliferation, restricted in the superficial dermis.
- Clinically, single, or multiple yellowish-white colored small popular lesions affecting the skin of the face and eyelids (most common areas).
- Some cases show a variable to significant amount of clear cell changes due to abundant glycogen in the cytoplasm. Clear cell variant is common in diabetes mellitus.
- In a small biopsy of a single lesion, the presence of small coma-shaped tubular structures in a dense desmoplastic stroma may mimic microcystic adnexal carcinoma. Evidence of keratin cysts, perineural invasion, and more infiltrative patterns in the deep dermis and subcutis favors microcystic adnexal carcinoma.
- Horn cysts filled with keratin are not seen in syringoma, while it is common in desmoplastic trichoepithelioma. Papillary mesenchymal bodies are seen in trichoepithelioma. Trichoepithelioma does not show true ductal differentiation.
- Lack of palisading arrangements of basaloid (blue) cells, retraction clefts around mucinous stroma, and mitoses in the present case, against the basal cell carcinoma of morphea type.
