Myoepithelial Carcinoma

J Cutan Pathol. 2007 Aug;34(8):648-53. Abstract quote

Background: Cutaneous myoepithelioma, both benign and malignant, is a rare neoplasm composed of neoplastic myoepithelial cells showing diverse histopathological features, and criteria for discriminating benign or malignant have not been fully clarified.

Patient: We present a case of cutaneous myoepithelial carcinoma in a 62-year-old woman presenting a solid mass in the right back.

Results: Resected tumor was located in the whole dermis and subcutis. Histopathologically, two different growth patterns were noted: a small-nested or trabecular pattern in the superficial part and a large nodular pattern with extensive central necrosis in the deep part. Tumor cells were all epithelioid, although plasmacytoid and glycogen-rich clear cells were also observed within the large nodules of the deep part. Immunohistochemically, the cells were positive for both epithelial and myogenic markers, suggesting myoepithelial origin. Lymphatic invasion and lymph node metastasis were evident despite inconspicuous atypia and low mitotic rate.

Conclusion: The final diagnosis was cutaneous myoepithelial carcinoma. At present, it seems to be difficult to predict the behavior of myoepithelioma of the skin and soft tissue, although atypia and high mitotic rate are reported to be associated with local recurrence and metastasis.

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/ Other Diagnostic Testing
Gross Appearance and Clinical Variants
Histopathological Features and Variants
Special Stains/ Immunohistochemistry/ Electron Microscopy
Differential Diagnosis
Prognosis
Treatment
Commonly Used Terms
Internet Links

CLINICAL/GROSS VARIANTS
SKIN
A case of cutaneous myoepithelial carcinoma. Tanahashi J, Kashima K, Daa T, Kondo Y, Kuratomi E, Yokoyama S. Department of Pathology, Faculty of Medicine, Oita University, Yufu City, Japan.	J Cutan Pathol. 2007 Aug;34(8):648-53. Abstract quote Background: Cutaneous myoepithelioma, both benign and malignant, is a rare neoplasm composed of neoplastic myoepithelial cells showing diverse histopathological features, and criteria for discriminating benign or malignant have not been fully clarified. Patient: We present a case of cutaneous myoepithelial carcinoma in a 62-year-old woman presenting a solid mass in the right back. Results: Resected tumor was located in the whole dermis and subcutis. Histopathologically, two different growth patterns were noted: a small-nested or trabecular pattern in the superficial part and a large nodular pattern with extensive central necrosis in the deep part. Tumor cells were all epithelioid, although plasmacytoid and glycogen-rich clear cells were also observed within the large nodules of the deep part. Immunohistochemically, the cells were positive for both epithelial and myogenic markers, suggesting myoepithelial origin. Lymphatic invasion and lymph node metastasis were evident despite inconspicuous atypia and low mitotic rate. Conclusion: The final diagnosis was cutaneous myoepithelial carcinoma. At present, it seems to be difficult to predict the behavior of myoepithelioma of the skin and soft tissue, although atypia and high mitotic rate are reported to be associated with local recurrence and metastasis.

HISTOPATHOLOGICAL VARIANTS	CHARACTERIZATION
GENERAL	Infiltrative multinodular growth pattern composed of cellular areas with epithelioid, hyaline, spindle, clear, and mixed cell types Majority (60%) are low grade cytology No true glands are formed There is a myxoid and/or hyalinized extracellular matrix. Mitotic figures range from 3-51 per 10 hpf. Necrosis, perineural, and vascular invasion are frequent. May have chondroid metaplasia, squamous and sebaceous metaplasia
VARIANTS
Clear cell	Histopathol 1996;28:309-315 Oral Surg Oral Med Oral Pathol 1991;72:200-207 Tight nests, hyalinized cords, trabeculate, vacuolated signet ring cell-like and lipoblast-like morphologies Usually mixed with other histological forms of myoepithelial carcinoma Tend to have more aggressive behavior with 50% recurrence rate and 40% metastatic rate to lung and scalp

SPECIAL STAINS/ IMMUNO-HISTOCHEMISTRY	CHARACTERIZATION
Immunostain	Percentage
AE1:AE3	100%
S-100 protein	100%
Vimentin	100%
34BetaE12	92%
CAM5.2	89%
Calponin	75%
Cytokeratin 14	53%
Smooth muscle actin	50%
GFAP	31%
EMA	21%
CEA	0%

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
Malignant mixed tumors
Polymorphous low grade adenocarcinoma of the salivary glands
Adenoid cystic carcinoma	Especially for the epithelioid type of myoepithelial carcinoma

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSIS	Am J Surg Pathol 2000;24:761-774. In spite of earlier studies dividing these tumors into low and high grade, there is no consistent association between the histology and behavior. In a follow up of 17 patients, the following results were obtained.
Outcome	Percentage
Metastases	47% (8/17)
Died of disease	29% (5/17) Mean 32 months
Alive with disease	12% (2/17)
Alive without disease	59% (10/17) Mean 42.2 months
TREATMENT	Complete excision