MAC on Cheek Clinical photograph of microcystic adnexal carcinoma (MAC) on the cheek of a middle-aged woman shows a flesh-colored papular to plaque-like lesion.
MAC at Low Magnification Scanning magnification of a microcystic adnexal carcinoma shows a diffusely infiltrative neoplasm in the dermis and extending into the dermal-subcutaneous interface .
MAC at Higher Magnification Higher magnification of the deep area of MAC shows infiltrative tumor nests and cords invading into the subcutaneous adipose tissue.
Perineural Invasion in MAC High magnification of a deep area of MAC shows tumor cell aggregates closely approaching a nerve .
TERMINOLOGY
Abbreviations
• Microcystic adnexal carcinoma (MAC)
Synonyms
• Sclerosing sweat duct carcinoma
• Syringoid carcinoma, malignant syringoma (older terms, should be avoided)
Definitions
• Low-grade malignant adnexal tumor with follicular and ductal differentiation
ETIOLOGY/PATHOGENESIS
Environmental Exposure
• Some cases may be related to solar damage (UV radiation) or radiation therapy
Higher incidence reported on left side of face, which receives greater solar exposure during driving
Unknown
• Most cases
CLINICAL ISSUES
Epidemiology
• Incidence
Uncommon adnexal tumors
• Age
Usually occur in middle-aged to older adults
• Sex
Slightly greater in females
Site
• Most common on face
Upper lip is most common site
• Can also occur on scalp, trunk, extremities, axillae, and groin
Presentation
• Indurated, plaque-like, or nodular lesion
Treatment
• Surgical approaches
Complete excision with clear margins
Mohs excision is effective and likely optimal approach in most cases
• Adjuvant therapy
Reports of effectiveness with adjuvant radiotherapy
Prognosis
• High incidence of local recurrence (up to 50%), but only very rare metastases
Metastases have been reported to local lymph nodes, but may represent local, deep invasion, rather than true metastasis
MACROSCOPIC
Size
• Typically measure > 1 cm in diameter
MICROSCOPIC
Histologic Features
• Bland-appearing, dermal-based adnexal tumor
• Deeply invasive and not well circumscribed
• Perineural invasion often present in deeper areas
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and cords invading into the subcutaneous adipose tissue.
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