Table 3 Morphological approach to benign cutaneous sweat gland lesions.
| Predominant morphology | Lesion | General features |
|---|---|---|
| Solid tumours with prominent basaloid component | Poroma, hidroacanthoma simplex and dermal duct tumour | Large nodules of monomorphic small “poroid” cells connected to the epidermis |
| Nodular hidradenoma | Large dermal nodules | |
| Cylindroma | Jigsaw‐puzzle appearance | |
| Thickened basement membrane | ||
| Spiradenoma | Basaloid cells with two cell types | |
| Cystic lesions | Hidrocystoma | Simple cyst lined by two rows of cells |
| Lining may have eccrine or apocrine epithelial features | ||
| Papillary projections or solid buds of secretory cells may be seen | ||
| Solid‐cystic tumours | Nodular hidradenoma | Solid lobules with cystic changes |
| May have spindle or squamous differentiation | ||
| Eosinophilic or clear cell change may be prominent | ||
| Mixed tumour of the skin | Tubular or anastomosing ductal/glandular proliferation | |
| Chondromyxoid stroma | ||
| Eccrine more common than apocrine | ||
| May also have “hamartomatous” components | ||
| Glandular tumours with eccrine differentiation | Syringoma | “Tadpole” or “comma shaped” small ducts with two rows of cells |
| Tubulopapillary hidradenoma with eccrine differentiation (papillary eccrine adenoma) | Dermal/subcutaneous tubular structures | |
| Intraluminal papillary projections | ||
| Syringofibroadenoma (acrosyringeal adenomatosis) | Diffuse proliferation of anastomosing acrosyringeal epithelium in epidermis and dermis | |
| Glandular tumours with apocrine differentiation | Hidradenoma papilliferum | Vulvar/perianal |
| Mostly in females | ||
| Prominent papillary fronds | ||
| Fibrous stroma | ||
| Tubulopapillary hidradenoma with apocrine differentiation (tubular apocrine adenoma and fibroadenoma) | Dermal/subcutaneous tubular apocrine structures | |
| Lobular pattern of with epidermal connection | ||
| Intraluminal papillary projections | ||
| SCAP | Mostly over scalp in young | |
| Elaborate epithelial papillary infolding | ||
| Open to epidermis | ||
| Plasma cell‐rich stroma | ||
| Apocrine differentiation is not always apparent | ||
| Tumours demonstrating clear cell change | Nodular hidradenoma | This may occur in many sweat gland tumours |
| Syringoma | Should be considered in conjunction with other features | |
| Poroma | Follicular lesions with trichilemmal differentiation are also in the differential | |
| Spiradenoma | ||
| Miscellaneous/hamartomatous/hyperplastic lesions | Apocrine/eccrine nevus | Localised proliferation of apocrine/eccrine glandular/ductal structures within deep dermis |
| Syringometaplasia | Mostly reaction to damaged eccrine ductal epithelium induced by different stimuli; especially chemotherapeutic drugs. Metaplasia of eccrine duct epithelium into squamous cells with intercellular bridges similar to the stratum spinosum | |
| Keratinisation and focal necrosis110 | ||
| Apocrine hyperplasia | Axillae and groin | |
| Nipple adenomatosis | Nipple | |
| Papillated ducts open to surface | ||
| Apocrine differentiation | ||
| Composite/mixed skin adnexal tumours | Have two or more lines of differentiation towards eccrine, apocrine, sebaceous or pilar structures |
SCAP, syringocystadenoma papilliferum.