New Variants of Epithelial-Myoepithelial Carcinoma: Oncocytic-Sebaceous and Apocrine

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      New Variants of Epithelial-Myoepithelial Carcinoma
                                       Oncocytic-Sebaceous and Apocrine
                   Raja R. Seethala, MD; Jeffrey A. Richmond, MD; Aaron P. Hoschar, MD; E. Leon Barnes, MD

● Context.—Recently described variants of epithelial-myo-              sebaceous elements. Phosphotungstic acid hematoxylin
epithelial carcinoma have not been well characterized but              staining, antimitochondrial antibody immunohistochemis-
raise a distinct set of differential diagnostic considerations         try, and ultrastructural examination confirm the abun-
than the classic type.                                                 dance of mitochondria in OEMCa but not in ApEMCa. The
   Objective.—To report a detailed analysis of oncocytic-              ductal component in ApEMCa was distinguished from that
sebaceous epithelial-myoepithelial carcinoma (OEMCa)                   of OEMCa by apical snouts, intracytoplasmic vacuoles, nu-
and a similar, but novel, variant, apocrine epithelial-myo-            clear pleomorphism, prominent nucleoli, and androgen re-
epithelial carcinoma (ApEMCa).                                         ceptor immunoreactivity.
   Design.—Clinical, histologic, and immunophenotypic                     Conclusions.—Oncocytic-sebaceous epithelial-myoepi-
features of 5 OEMCas and 5 ApEMCas were analyzed. Ul-                  thelial carcinoma and ApEMCa should be considered in the
trastructural examination was also performed on 3 OEMCa
                                                                       differential diagnosis of oncocytic/oncocytoid salivary
and 1 ApEMCa tumors.
   Results.—The mean age for OEMCa (74.4 years; range,                 gland tumors. Oncocytic-sebaceous epithelial-myoepithe-
58–82 years) was slightly higher than for ApEMCa (61.6;                lial carcinoma morphology may reflect a senescent phe-
range, 46–79 years). All tumors arose in the parotid glands            notype, similar to other oncocytic lesions. The ductal com-
and demonstrated a multinodular pattern of growth with                 ponent of ApEMCa shares some similarities with salivary
an average size of 3.3 cm (range, 2.3–6.5 cm). Available               duct carcinoma and supports the notion that epithelial-
follow-up (n      6; 3 OEMCas, 3 ApEMCas) shows a favor-               myoepithelial carcinoma can serve as the progenitor tumor
able course (no evidence of disease; mean, 17.4 months).               for hybrid tumors.
Both were morphologically similar, but only OEMCa had                     (Arch Pathol Lab Med. 2009;133:950–959)


E  pithelial-myoepithelial carcinoma (EMCa) is an uncom-
     mon, biphasic salivary gland malignancy composed
of ductal epithelial cells and myoepithelial cells with a
                                                                       epithelial component and sebaceous elements, populated
                                                                       8% of all our EMCa.4 The cells in this variant are true
                                                                       oncocytes because the prominent granular, eosinophilic
broad morphologic spectrum. In the classic definition of                cytoplasm is constituted by abundant mitochondria. Sub-
EMCa, the myoepithelial component consists of polygonal                sequent to that publication, we encountered several EMCa
cells with clear cytoplasm, whereas the ductal component               that were, at first glance, very similar to OEMCa in terms
is composed of small lumina lined by cuboidal, mildly                  of the abundant granular, eosinophilic cytoplasm. How-
eosinophilic cells reminiscent of intercalated ducts.1–3               ever, unlike the oncocytes in OEMCa, these cells could
However in our previously reported series of 61 cases,4 we             only be considered ‘‘oncocytoid’’ because they did not
had observed a much broader morphologic spectrum with                  quite show the same degree of granularity or abundant
respect to cytoplasmic characteristics, relative cell type             mitochondria by histochemical or immunohistochemical
proportion, and pattern of arrangement. As a result, sev-              stains. Additionally, these cells showed periapical snouts,
eral new and rediscovered histologic variants emerged.                 vacuolated cytoplasm, and nuclei with prominent cent
				
DOCUMENT INFO
Description: CONTEXT: Recently described variants of epithelial-myoepithelial carcinoma have not been well characterized but raise a distinct set of differential diagnostic considerations than the classic type. OBJECTIVE: To report a detailed analysis of oncocytic-sebaceous epithelial-myoepithelial carcinoma (OEMCa) and a similar, but novel, variant, apocrine epithelial-myoepithelial carcinoma (ApEMCa). DESIGN: Clinical, histologic, and immunophenotypic features of 5 OEMCas and 5 ApEMCas were analyzed. Ultrastructural examination was also performed on 3 OEMCa and 1 ApEMCa tumors. RESULTS: The mean age for OEMCa (74.4 years; range, 58-82 years) was slightly higher than for ApEMCa (61.6; range, 46-79 years). All tumors arose in the parotid glands and demonstrated a multinodular pattern of growth with an average size of 3.3 cm (range, 2.3-6.5 cm). Available follow-up (n = 6; 3 OEMCas, 3 ApEMCas) shows a favorable course (no evidence of disease; mean, 17.4 months). Both were morphologically similar, but only OEMCa had sebaceous elements. Phosphotungstic acid hematoxylin staining, antimitochondrial antibody immunohistochemistry, and ultrastructural examination confirm the abundance of mitochondria in OEMCa but not in ApEMCa. The ductal component in ApEMCa was distinguished from that of OEMCa by apical snouts, intracytoplasmic vacuoles, nuclear pleomorphism, prominent nucleoli, and androgen receptor immunoreactivity. CONCLUSIONS: Oncocytic-sebaceous epithelial-myoepithelial carcinoma and ApEMCa should be considered in the differential diagnosis of oncocytic/oncocytoid salivary gland tumors. Oncocytic-sebaceous epithelial-myoepithelial carcinoma morphology may reflect a senescent phenotype, similar to other oncocytic lesions. The ductal component of ApEMCa shares some similarities with salivary duct carcinoma and supports the notion that epithelial-myoepithelial carcinoma can serve as the progenitor tumor for hybrid tumors.
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