PMC9905423_01
(A, C): Mammogram of the right breast showing an 8 x 8mm partly circumscribed nodule in the right axillary tail, corresponding to the intramammary lymph mode on ultrasound. Abnormal lymph nodes are also seen in bilateral axillae, denser on the right. (B, D): Mammogram of the left breast showing a vague asymmetric density in the upper outer quadrant, corresponding to the palpable lump. The overlying skin is thickened with slight retraction of the nipple.
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Mammogram ( Figure 1 ) found a vague asymmetric density in the left upper outer quadrant, corresponding to the palpable lump.
(A-D) Ultrasound images of the left breast showing multiple ill-defined heterogeneously hypoechoic lesions extending from the 11 o'clock to 3 o'clock position. (E, F) Ultrasound images of bilateral axilla showing abnormal axillary lymphadenopathy.
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Breast ultrasound revealed multiple vague and ill-defined heterogeneously hypoechoic lesions extending from the 11 to 3 o'clock positions of the left breast ( Figures 2A-D ). In addition, abnormal intramammary lymph nodes were present in the right breast upper outer quadrant, and there were also multiple abnormal lymph nodes in both axillae, compatible with metastasis ( Figures 2E, F ).
H&E-stained sections at 100x magnification of (A) the endometrial curettage specimen, showing high-grade endometrial carcinoma with clear cell features. Fragments of tumor tissue are seen with tubulo-papillary and glandular architecture with a hobnailed appearance. The cells contain nuclear atypia, pleomorphism, and prominent nucleoli with areas of clear cytoplasm. (B) The breast tumor shows similar morphology to the endometrial tumor in 
Figure 3
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Interestingly, both the breast and endometrial lesions had significant morphologic resemblance on histology ( Figure 3 ).
Immunohistochemical stains show similarities in the endometrial and breast tumor. (A) The endometrial tumor stains negative for GATA-3 (a breast marker). (B) Similarly, the breast tumor also stains negative for GATA-3, although the adjacent breast ducts are positive. (C, E) show that the endometrial tumor stains positive for PAX8 (marker for Mullerian tumors) and napsin A (marker for clear cell carcinoma). In (D, F) the breast tumor similarly stains positive for PAX8 and napsin A, whereas the adjacent breast tissues are negative.
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Immunohistochemical staining of the left breast tumor and right axillary lymph node ( Figures 4 ,  5 ) showed negative results for breast markers GATA-3 and mammaglobin but showed diffusely positive results for PAX8, which is frequently expressed in endometrial carcinoma.
Immunohistochemical stains show that both the (A) endometrial and (B) breast tumors stain positive for estrogen receptor (ER). (C) The breast tumor is negative for HER2 expression, and (D) the endometrial tumor does not express mammaglobin, a breast marker.
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Immunohistochemical staining of the left breast tumor and right axillary lymph node ( Figures 4 ,  5 ) showed negative results for breast markers GATA-3 and mammaglobin but showed diffusely positive results for PAX8, which is frequently expressed in endometrial carcinoma.