http://www.histopathology-india.net/SwCa.htm

Cysts:

Hydrocystoma -Eccrine/Apocrine

Hamartomas:

Eccrine/Apocrine naevus

Eccrine Angiomatous Hamartoma

Porokeratotic eccrine ostial naevus

Benign Neoplasms:

Syringocystadenoma Papilliferum

Hidradenoma Papilliferum

Nipple Adenoma

Syringoma

Spiradenoma

Cylindroma

Chondroid Syringoma (benign mixed tumour)

Poroma

Hidradenoma

Apocrine adenoma

Papillary eccrine adenoma

Syringofibroadenoma

Adenoid cystic carcinomas are regarded by some authors as apocrine in origin.

Site: 

Located on the scalp and on the chest. Rarely the tumour arises from the skin of the eyelid.

Adenoid Cystic Carcinoma of the External Ear ; Pulmonary Adenoid Cystic Carcinoma.

Microscopic features:

  Images:(dermatopathology cases)

- Cords of basaloid cells arranged in a cribiform pattern.
- Focal tubular areas.
- Cystic spaces containing basophilic mucinous material.
- Perineural invasion is an important feature.

Immunohistochemistry:

Epithelial membrane antigen:  Positive
CEA : sometimes positive
Cytokeratin, vimentin and S100 protein :  focal positive staining

Differential diagnoses: 

1. Adenoid basal cell carcinoma: [Adenoid cystic carcinoma is characterized by:   Absence of retraction artefact , absence of contiguity with the epidermis or hair sheaths ,  lack of peripheral palisading of the nuclei, and occasional presence of central apoptotic or even necrotic cells. Pseudocysts stain positively to Alcian blue and periodic acid-Schiff ].

2. Primary cutaneous cribriform carcinoma: 

Primary cutaneous cribriform carcinoma: a rare apocrine tumour.J Cutan Pathol. 2005 Sep;32(8):577-80.

Unlike most of the sweat gland carcinomas, this tumour tends to recur locally and rarely spreads to lymph nodes or distant organs.

Primary cutaneous adenoid cystic carcinoma metastatic to cervical lymph nodes.Head Neck. 2000 Jan;22(1):84-6

Primary cutaneous adenoid cystic carcinoma of the eyelid.Am J Ophthalmol. 2001 Feb;131(2):281-3.

Primary cutaneous adenoid cystic carcinoma with lymphnode metastasis. Am J  Dermatopathol 1998; 20: 571-577   

. A comparative immunohistochemical study of adenoid cystic carcinoma of the skin and salivary glands. Am J Dermatopathol 1991;13: 162-168

Primary adenoid cystic carcinoma masquerading as syringoma of the scalp. Am J Dermatopathol. 1990; 12: 169-174

Primary adenoid cystic carcinoma : case report,  immunohistochemistry, and review of the literature. Br J Dermatol 1988; 118: 567-578  

Primary cutaneous adenoid cystic carcinoma. J Am Acad Dermatol 1987; 17: 113-118 

Primary adenoid cystic carcinoma of the skin.  A clinical, histological and immunohistochemical comparison with adenoid cystic carcinoma of salivary glands and adenoid basal cell carcinoma. Am J Dermatopathol 1986; 8: 2-13

Primary cutaneous adenoid cystic carcinoma. Arch Dermatol 1984; 120: 774-777 

Adenoid cystic carcinoma involving the external auditory canal. A clinicopathologic study of 16 cases. Cancer 1982; 50: 2873-2883

Sweat-gland carcinomas: prognosis related to histological type. Histopathology 1980; 4: 445-466

Hair Germ Differentiation:

Trichoepithelioma 

Desmoplastic  Trichoepithelioma

Trichofolliculoma

Trichoblastoma

Cutaneous lymphadenoma

Infundibular differentiation:

Trichoadenoma

Dilated Pore of Winer

Pilar Sheath Acanthoma

Tumour of Follicular Infundibulum

Outer root sheath differentiation:
                    
Trichilemmoma

Trichilemmal Carcinoma

Proliferating Trichilemmal Cyst (Pilar Tumour)