Radiological investigations revealed a lytic lesion in the left acetabulum. A computerised tomography (CT)-guided biopsy was obtained from the lesion. The histopathological examination of the hematoxylin and eosin (H&E) stained sections revealed occasional fragments of dead bone with a few clusters of round to polygonal tumor cells with mild cellular pleomorphism, eccentrically placed round nuclei, coarse chromatin, occasional prominent nucleoli, and a moderate amount of cytoplasm. Immunohistochemistry revealed the tumor cells to be positive for cytokeratin-7 (CK7) and GATA3 and negative for TTF1 and p63 (Figure 1A-D). Based on the histopathological and immunohistochemical features, a diagnosis of metastatic carcinoma was rendered, with a suggestion of a primary of breast origin. Following this, the patient was workedup for confirming the breast primary. However, clinical examination, mammography and positron emission tomography (PET) all failed to identify any lesion in the breast or lungs.
Consequently, FNAC from the right cervical swelling was advised and simultaneously a sample for cell-block preparation was also collected. The smears were cellular and showed tumor cells predominantly dispersed singly as well as arranged in loose clusters in a background of chondromyxoid stroma. The tumor cells were round to polygonal with mild pleomorphism, eccentrically placed round nuclei, coarse chromatin, occasional prominent nucleoli, and a moderate amount of cytoplasm with some showing cytoplasmic vacuolations. Additionally, occasional loose clusters of relatively smaller cells with scant cytoplasm were also noted (Figure 2A-D). The H&E stained section from the cell-block revealed tumor cells arranged in the form of tubules lined by a dual layer of tumor cells. The luminal cells showed a scant to moderate amount of pale to eosinophilic cytoplasm and the basally placed cells showed a moderate amount of clear to vacuolated cytoplasm. A few scattered mitotic figures and occasional lymphoid aggregates were also noted. On performing IHC, the luminal cells showed strong diffuse membranous positivity for CK7 (epithelial marker) and the abluminal cells showed strong nuclear positivity for p63 (myoepithelial marker). Less than 10% of tumor cells showed nuclear positivity for GATA3 (Figure 3A-F). Based on the cytomorphological features on smears and cellblock and the immunocytochemistry, a final diagnosis of metastatic epithelial-myoepithelial carcinoma was given.
The major differential diagnoses on cytomorphology include pleomorphic adenoma, myoepithelioma and plasmacytoma, especially when the myoepithelial component predominates in the smears. Cell-block sections can provide useful information regarding the tumor cell architecture, as was evident in the index case. Additionally, immunohistochemistry can be performed on the cell-block sections for supplementing the morphologic diagnosis. A valuable learning point highlighted by the present report is that nuclear positivity for GATA3 should not always be recognized as an indicator of breast or urinary bladder origin. It is important to remember that variable GATA3 positivity can also be seen in some of the salivary gland neoplasms. Although amongst the salivary neoplasms, salivary duct carcinoma and mammary analogue secretory carcinoma show the most consistent immunostaining for GATA3 but the same can also be seen in EMCs [10,11]. Hence the need to include salivary gland neoplasms in the list of differential diagnoses for cases with GATA3 positivity.
In conclusion, the present report, in addition to highlighting the cytomorphological and immunocytochemical features of EMC, reemphasizes the diagnostic utility of FNAC as a minimally invasive technique for diagnosis of such challenging cases.
CONFLICT of INTEREST
The authors declare no conflict of interest.
AUTHORSHIP CONTRIBUTIONS
Concept: PG, Design: PG, AR, Data collection or
processing: PG, NK, AR, Analysis or Interpretation: PG,
NK, AR, Literature search: PG, Writing: PG, Approval: PG,
NK, AR.
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