Pathology of Microcystic Adnexal Carcinoma

Dr Sampurna Roy MD                                    2022   

Microcystic Adnexal Carcinoma a slow growing locally aggressive adnexal tumour was first reported by Goldstein et al, in 1982. 

This tumour shows both eccrine and pilar differentiation.

However, it has been recently regarded as an apocrine tumour.

Clinical presentation:

The tumour usually presents as skin coloured indurated plaque or nodule.

Site:

The lesion usually occurs on the upper lip or elsewhere on the face. It is also noted in the axilla, extremities, genital skin, trunk and scalp.

Locally Aggressive Adnexal Tumour- Microcystic Adnexal Carcinoma [Pathology Infographic

Microscopic features: Microscopically, this infiltrating tumour involves the dermis, subcutis and may also extend into the underlying muscle. The superficial part is composed of numerous  keratinous cysts. Solid islands and strands of basaloid and squamous cells alternate with the cysts. These cells may show ductal differentiation. Focal microcalcification, clear cell changes, prominent lumina and  arborizing tubules may be present. In the mid dermis, the basaloid strand and ducts are prominent but the keratinous cysts are diminished in number. Focally sebaceous and follicular differentiation may be seen. The deeper component has a schirrous appearance and shows smaller  nests and strands of cells in a dense hyalinized stroma. The epithelial elements are diminished to small clusters of 2 or 3 cells. Cytologically the tumour cells are of uniform size. Mitotic figures are rarely seen. Prominent glandular component may be present (known as sclerosing sweat duct carcinoma or malignant syringoma). Immunohistochemistry:  Epithelial membrane antigen - positive   Immunohistochemically the luminal cells express CEA. The tumour stain positively for Ber-EP4. The tumour cells also stain for EMA and various cytokeratins (particularly CK7 and CK15). Some S100 positive cells are present, but the stroma is CD34 negative. (Differential diagnosis: In Desmoplastic trichoepithelioma the stroma may be CD34 positive). Low level of Ki 67 indicates low proliferative index. In Microcystic Adnexal Carcinoma, calcifications, granulomas, connection to follicles, keratin expression pattern, PHLDA1 positivity and K77 negativity indicate a follicular histogenesis.

Differential Diagnosis:

Desmoplastic trichoepithelioma, morpheic basal cell carcinoma, metastatic breast carcinoma, syringoma, papillary eccrine adenoma.

Desmoplastic trichoepithelioma and syringoma do not show evidence of aggressive growth pattern and perineural spread.

It is not possible to give a definitive diagnosis in shave or superficial punch biopsies.

In morpheic basal cell carcinoma there is no lumen formation or zonation  of the tumour.

Mohs micrograph surgery is the current treatment of choice. Local recurrence occurs in 50% cases.

This is less likely if excision margins are free of tumour in the initial biopsy.

Malignant sweat gland tumours: an update

Anatomoclinical study of 30 cases of sclerosing sweat duct carcinomas (microcystic adnexal carcinoma, syringomatous carcinoma and squamoid eccrine ductal carcinoma).

Microcystic adnexal carcinoma simulating scarring alopecia.

Longtime undetected microcystic adnexal carcinoma of the scalp: considerations and implications.

Expression of p75 neurotrophin receptor in desmoplastic trichoepithelioma, infiltrative basal cell carcinoma, and microcystic adnexal carcinoma.

The immunohistochemical differential diagnosis of microcystic adnexal carcinoma, desmoplastic trichoepithelioma and morpheaform basal cell carcinoma using BerEP4 and stem cell markers.

Microcystic adnexal carcinoma of the upper lip misdiagnosed benign desmoplastic trichoepithelioma.

Microcystic adnexal carcinoma versus desmoplastic trichoepithelioma: a comparative study.